VOLUME XI, SLICE V

Gassendi, Pierre to Geocentric

ARTICLES IN THIS SLICE:

GASSENDI, PIERRE GEFLE GASTEIN GEGENBAUR, CARL GASTRIC ULCER GEGENSCHEIN GASTRITIS GEIBEL, EMANUEL GASTROPODA GEIGE GASTROTRICHA GEIGER, ABRAHAM GATAKER, THOMAS GEIJER, ERIK GUSTAF GATCHINA GEIKIE, SIR ARCHIBALD GATE GEIKIE, JAMES GATEHOUSE GEIKIE, WALTER GATES, HORATIO GEILER VON KAISERSBERG, JOHANN GATESHEAD GEINITZ, HANS BRUNO GATH GEISHA GATLING, RICHARD JORDAN GEISLINGEN GATTY, MARGARET GEISSLER, HEINRICH GAU, JOHN GELA GAUDEN, JOHN GELADA GAUDICHAUD-BEAUPRÉ, CHARLES GELASIUS GAUDRY, JEAN ALBERT GELATI GAUDY GELATIN GAUERMANN, FRIEDRICH GELDERLAND (duchy) GAUGE GELDERLAND (province of Holland) GAUHATI GELDERN GAUL, GILBERT WILLIAM GELL, SIR WILLIAM GAUL GELLERT, CHRISTIAN FÜRCHTEGOTT GAULT GELLERT GAUNTLET GELLIUS, AULUS GAUR (ruined city of India) GELLIVARA GAUR (wild ox) GELNHAUSEN GAUSS, KARL FRIEDRICH GELO GAUSSEN, FRANÇOIS SAMUEL LOUIS GELSEMIUM GAUTIER, ÉMILE THÉODORE LÉON GELSENKIRCHEN GAUTIER, THÉOPHILE GEM GAUTIER D'ARRAS GEM, ARTIFICIAL GAUZE GEMBLOUX GAVARNI GEMINI GAVAZZI, ALESSANDRO GEMINIANI, FRANCESCO GAVELKIND GEMISTUS PLETHO, GEORGIUS GAVESTON, PIERS GEMMI PASS GAVOTTE GENDARMERIE GAWAIN GENEALOGY GAWLER GENELLI, GIOVANNI BUONAVENTURA GAY, JOHN GENERAL GAY, MARIE FRANÇOISE SOPHIE GENERATION GAY, WALTER GENESIS GAYA GENET GAYAL GENEVA (New York, U.S.A.) GAYANGOS Y ARCE, PASCUAL DE GENEVA (Switzerland) GAYARRÉ, CHARLES ÉTIENNE ARTHUR GENEVA CONVENTION GAY-LUSSAC, JOSEPH LOUIS GENEVA, LAKE OF GAZA, THEODORUS GENEVIÈVE, ST GAZA GENEVIÈVE, OF BRABANT GAZALAND GENGA, GIROLAMO GAZEBO GENISTA GAZETTE GENIUS GEAR GENUS, STÉPHANIE DE SAINT-AUBIN GEBER GENNA GEBHARD TRUCHSESS VON WALDBURG GENNADIUS II. GEBWEILER GENOA GECKO GENOVESI, ANTONIO GED, WILLIAM GENSONNÉ, ARMAND GEDDES, ALEXANDER GENTIAN GEDDES, ANDREW GENTIANACEAE GEDDES, JAMES LORRAINE GENTILE GEDDES, SIR WILLIAM DUGUID GENTILE DA FABRIANO GEDYMIN GENTILESCHI, ARTEMISIA and ORAZIO DE' GEE, THOMAS GENTILI, ALBERICO GEEL, JACOB GENTLE GEELONG GENTLEMAN GEESTEMÜNDE GENTZ, FRIEDRICH VON GEFFCKEN, FRIEDRICH HEINRICH GEOCENTRIC GEFFROY, MATHIEU AUGUSTE

GASSENDI[1] [GASSEND], PIERRE (1592-1655), French philosopher, scientist and mathematician, was born of poor parents at Champtercier, near Digne, in Provence, on the 22nd of January 1592. At a very early age he gave indications of remarkable mental powers and was sent to the college at Digne. He showed particular aptitude for languages and mathematics, and it is said that at the age of sixteen he was invited to lecture on rhetoric at the college. Soon afterwards he entered the university of Aix, to study philosophy under P. Fesaye. In 1612 he was called to the college of Digne to lecture on theology. Four years later he received the degree of doctor of theology at Avignon, and in 1617 he took holy orders. In the same year he was called to the chair of philosophy at Aix, and seems gradually to have withdrawn from theology. He lectured principally on the Aristotelian philosophy, conforming as far as possible to the orthodox methods. At the same time, however, he followed with interest the discoveries of Galileo and Kepler, and became more and more dissatisfied with the Peripatetic system. It was the period of revolt against the Aristotelianism of the schools, and Gassendi shared to the full the empirical tendencies of the age. He, too, began to draw up objections to the Aristotelian philosophy, but did not at first venture to publish them. In 1624, however, after he had left Aix for a canonry at Grenoble, he printed the first part of his _Exercitationes paradoxicae adversus Aristoteleos_. A fragment of the second book was published later at La Haye (1659), but the remaining five were never composed, Gassendi apparently thinking that after the _Discussiones Peripateticae_ of Francesco Patrizzi little field was left for his labours.

After 1628 Gassendi travelled in Flanders and Holland. During this time he wrote, at the instance of Mersenne, his examination of the mystical philosophy of Robert Fludd (_Epistolica dissertatio in qua praecipua principia philosophiae Ro. Fluddi deteguntur_, 1631), an essay on parhelia (_Epistola de parheliis_), and some valuable observations on the transit of Mercury which had been foretold by Kepler. He returned to France in 1631, and two years later became provost of the cathedral church at Digne. Some years were then spent in travelling through Provence with the duke of Angoulême, governor of the department. The only literary work of this period is the _Life of Peiresc_, which has been frequently reprinted, and was translated into English. In 1642 he was engaged by Mersenne in controversy with Descartes. His objections to the fundamental propositions of Descartes were published in 1642; they appear as the fifth in the series contained in the works of Descartes. In these objections Gassendi's tendency towards the empirical school of speculation appears more pronounced than in any of his other writings. In 1645 he accepted the chair of mathematics in the Collège Royal at Paris, and lectured for many years with great success. In addition to controversial writings on physical questions, there appeared during this period the first of the works by which he is known in the history of philosophy. In 1647 he published the treatise _De vita, moribus, et doctrina Epicuri libri octo_. The work was well received, and two years later appeared his commentary on the tenth book of Diogenes Laërtius, _De vita, moribus, et placitis Epicuri, seu Animadversiones in X. librum Diog. Laër_. (Lyons, 1649; last edition, 1675). In the same year the more important _Syntagma philosophiae Epicuri_ (Lyons, 1649; Amsterdam, 1684) was published.

In 1648 ill-health compelled him to give up his lectures at the Collège Royal. He travelled in the south of France, spending nearly two years at Toulon, the climate of which suited him. In 1653 he returned to Paris and resumed his literary work, publishing in that year lives of Copernicus and Tycho Brahe. The disease from which he suffered, lung complaint, had, however, established a firm hold on him. His strength gradually failed, and he died at Paris on the 24th of October 1655. A bronze statue of him was erected by subscription at Digne in 1852.

His collected works, of which the most important is the _Syntagma philosophicum_ (_Opera_, i. and ii.), were published in 1658 by Montmort (6 vols., Lyons). Another edition, also in 6 folio volumes, was published by N. Averanius in 1727. The first two are occupied entirely with his _Syntagma philosophicum_; the third contains his critical writings on Epicurus, Aristotle, Descartes, Fludd and Lord Herbert, with some occasional pieces on certain problems of physics; the fourth, his _Institutio astronomica_, and his _Commentarii de rebus celestibus_; the fifth, his commentary on the tenth book of Diogenes Laërtius, the biographies of Epicurus, N.C.F. de Peiresc, Tycho Brahe, Copernicus, Georg von Peuerbach, and Regiomontanus, with some tracts on the value of ancient money, on the Roman calendar, and on the theory of music, to all which is appended a large and prolix piece entitled _Notitia ecclesiae Diniensis_; the sixth volume contains his correspondence. The _Lives_, especially those of Copernicus, Tycho and Peiresc, have been justly admired. That of Peiresc has been repeatedly printed; it has also been translated into English. Gassendi was one of the first after the revival of letters who treated the _literature_ of philosophy in a lively way. His writings of this kind, though too laudatory and somewhat diffuse, have great merit; they abound in those anecdotal details, natural yet not obvious reflections, and vivacious turns of thought, which made Gibbon style him, with some extravagance certainly, though it was true enough up to Gassendi's time--"le meilleur philosophe des littérateurs, et le meilleur littérateur des philosophes."

Gassendi holds an honourable place in the history of physical science. He certainly added little to the stock of human knowledge, but the clearness of his exposition and the manner in which he, like Bacon, urged the importance of experimental research, were of inestimable service to the cause of science. To what extent any place can be assigned him in the history of philosophy is more doubtful. The _Exercitationes_ on the whole seem to have excited more attention than they deserved. They contain little or nothing beyond what had been already advanced against Aristotle. The first book expounds clearly, and with much vigour, the evil effects of the blind acceptance of the Aristotelian dicta on physical and philosophical study; but, as is the case with so many of the anti-Aristotelian works of this period, the objections show the usual ignorance of Aristotle's own writings. The second book, which contains the review of Aristotle's dialectic or logic, is throughout Ramist in tone and method. The objections to Descartes--one of which at least, through Descartes's statement of it in the appendix of objections in the _Meditationes_ has become famous--have no speculative value, and in general are the outcome of the crudest empiricism. His labours on Epicurus have a certain historical value, but the want of consistency inherent in the philosophical system raised on Epicureanism is such as to deprive it of genuine worth. Along with strong expressions of empiricism we find him holding doctrines absolutely irreconcilable with empiricism in any form. For while he maintains constantly his favourite maxim "that there is nothing in the intellect which has not been in the senses" (_nihil in intellectu quod non prius fuerit in sensu_), while he contends that the imaginative faculty (_phantasia_) is the counterpart of sense--that, as it has to do with material images, it is itself, like sense, material, and essentially the same both in men and brutes; he at the same time admits that the intellect, which he affirms to be immaterial and immortal--the most characteristic distinction of humanity--attains notions and truths of which no effort of sensation or imagination can give us the slightest apprehension (Op. ii. 383). He instances the capacity of forming "general notions"; the very conception of universality itself (_ib._ 384), to which he says brutes, who partake as truly as men in the faculty called _phantasia_, never attain; the notion of God, whom he says we may imagine to be corporeal, but understand to be incorporeal; and lastly, the reflex action by which the mind makes its own phenomena and operations the objects of attention.

The _Syntagma philosophicum_, in fact, is one of those eclectic systems which unite, or rather place in juxtaposition, irreconcilable dogmas from various schools of thought. It is divided, according to the usual fashion of the Epicureans, into logic (which, with Gassendi as with Epicurus, is truly _canonic_), physics and ethics. The logic, which contains at least one praiseworthy portion, a sketch of the history of the science, is divided into theory of right apprehension (_bene imaginari_), theory of right judgment (_bene proponere_), theory of right inference (_bene colligere_), theory of right method (_bene ordinare_). The first part contains the specially empirical positions which Gassendi afterwards neglects or leaves out of account. The senses, the sole source of knowledge, are supposed to yield us immediately cognition of individual things; phantasy (which Gassendi takes to be material in nature) reproduces these ideas; understanding compares these ideas, which are particular, and frames general ideas. Nevertheless, he at the same time admits that the senses yield knowledge--not of things--but of qualities only, and holds that we arrive at the idea of thing or substance by induction. He holds that the true method of research is the analytic, rising from lower to higher notions; yet he sees clearly, and admits, that inductive reasoning, as conceived by Bacon, rests on a general proposition not itself proved by induction. He ought to hold, and in disputing with Descartes he did apparently hold, that the evidence of the senses is the only convincing evidence; yet he maintains, and from his special mathematical training it was natural he should maintain, that the evidence of reason is absolutely satisfactory. The whole doctrine of judgment, syllogism and method is a mixture of Aristotelian and Ramist notions.

In the second part of the _Syntagma_, the physics, there is more that deserves attention; but here, too, appears in the most glaring manner the inner contradiction between Gassendi's fundamental principles. While approving of the Epicurean physics, he rejects altogether the Epicurean negation of God and particular providence. He states the various proofs for the existence of an immaterial, infinite, supreme Being, asserts that this Being is the author of the visible universe, and strongly defends the doctrine of the foreknowledge and particular providence of God. At the same time he holds, in opposition to Epicureanism, the doctrine of an immaterial rational soul, endowed with immortality and capable of free determination. It is altogether impossible to assent to the supposition of Lange (_Gesch. des Materialismus_, 3rd ed., i. 233), that all this portion of Gassendi's system contains nothing of his own opinions, but is introduced solely from motives of self-defence. The positive exposition of atomism has much that is attractive, but the hypothesis of the _calor vitalis_ (vital heat), a species of _anima mundi_ (world-soul) which is introduced as physical explanation of physical phenomena, does not seem to throw much light on the special problems which it is invoked to solve. Nor is his theory of the weight essential to atoms as being due to an inner force impelling them to motion in any way reconcilable with his general doctrine of mechanical causes.

In the third part, the ethics, over and above the discussion on freedom, which on the whole is indefinite, there is little beyond a milder statement of the Epicurean moral code. The final end of life is happiness, and happiness is harmony of soul and body (_tranquillitas animi et indolentia corporis_). Probably, Gassendi thinks, perfect happiness is not attainable in this life, but it may be in the life to come.

The _Syntagma_ is thus an essentially unsystematic work, and clearly exhibits the main characteristics of Gassendi's genius. He was critical rather than constructive, widely read and trained thoroughly both in languages and in science, but deficient in speculative power and original force. Even in the department of natural science he shows the same inability steadfastly to retain principles and to work from them; he wavers between the systems of Brahe and Copernicus. That his revival of Epicureanism had an important influence on the general thinking of the 17th century may be admitted; that it has any real importance in the history of philosophy cannot be granted.

AUTHORITIES.--Gassendi's life is given by Sorbière in the first collected edition of the works, by Bugerel, _Vie de Gassendi_ (1737; 2nd ed., 1770), and by Damiron, _Mémoire sur Gassendi_ (1839). An abridgment of his philosophy was given by his friend, the celebrated traveller, Bernier (_Abrégé de la philosophie de Gassendi_, 8 vols., 1678; 2nd ed., 7 vols., 1684). The most complete surveys of his work are those of G.S. Brett (_Philosophy of Gassendi_, London, 1908), Buhle (_Geschichte der neuern Philosophie_, iii. 1, 87-222), Damiron (_Mémoires pour servir à l'histoire de philosophie au XVII^e siècle_), and P.F. Thomas (_La Philosophie de Gassendi_, Paris, 1889). See also Ritter, _Geschichte der Philosophie_, x. 543-571; Feuerbach, _Gesch. d. neu. Phil. von Bacon bis Spinoza_, 127-150; F.X. Kiefl, _P. Gassendis Erkenntnistheorie und seine Stellung zum Materialismus_ (1893) and "Gassendi's Skepticismus" in _Philos. Jahrb._ vi. (1893); C. Güttler, "Gassend oder Gassendi?" in _Archiv f. Gesch. d. Philos._ x. (1897), pp. 238-242. (R. Ad.; X.)

FOOTNOTE:

[1] It was formerly thought that _Gassendi_ was really the genitive of the Latin form _Gassendus_. C. Güttler, however, holds that it is a modernized form of the O. Fr. _Gassendy_ (see paper quoted in bibliography).

GASTEIN, in the duchy of Salzburg, Austria, a side valley of the Pongau or Upper Salzach, about 25 m. long and 1¼ m. broad, renowned for its mineral springs. It has an elevation of between 3000 and 3500 ft. Behind it, to the S., tower the mountains Mallnitz or Nassfeld-Tauern (7907 ft.) and Ankogel (10,673 ft.), and from the right and left of these mountains two smaller ranges run northwards forming its two side walls. The river Ache traverses the valley, and near Wildbad-Gastein forms two magnificent waterfalls, the upper, the Kesselfall (196 ft.), and the lower, the Bärenfall (296 ft.). Near these falls is the Schleierfall (250 ft.), formed by the stream which drains the Bockhart-see. The valley is also traversed by the so-called Tauern railway (opened up to Wildbad-Gastein in September 1905), which goes to Mallnitz, piercing the Tauern range by a tunnel 9260 yds. in length. The principal villages of the valley are Hof-Gastein, Wildbad-Gastein and Böckstein.

HOF-GASTEIN, pop. (1900) 840, the capital of the valley, is also a watering-place, the thermal waters being conveyed here from Wildbad-Gastein by a conduit 5 m. long, constructed in 1828 by the emperor Francis I. of Austria. Hof-Gastein was, after Salzburg, the richest place in the duchy, owing to its gold and silver mines, which were already worked during the Roman period. During the 16th century these mines were yielding annually 1180 lb. of gold and 9500 lb. of silver, but since the 17th century they have been much neglected and many of them are now covered by glaciers.

WILDBAD-GASTEIN, commonly called _Bad-Gastein_, one of the most celebrated watering-places in Europe, is picturesquely situated in the narrow valley of the Gasteiner Ache, at an altitude of 3480 ft. The thermal springs, which issue from the granite mountains, have a temperature of 77°-120° F., and yield about 880,000 gallons of water daily. The water contains only 0.35 to 1000 of mineral ingredients and is used for bathing purposes. The springs are resorted to in cases of nervous affections, senile and general debility, skin diseases, gout and rheumatism. Wildbad-Gastein is annually visited by over 8500 guests. The springs were known as early as the 7th century, but first came into fame by a successful visit paid to them by Duke Frederick of Austria in 1436. Gastein was a favourite resort of William I. of Prussia and of the Austrian imperial family, and it was here that, on the 14th of August 1865, was signed the agreement known as the Gastein Convention, which by dividing the administration of the conquered provinces of Schleswig and Holstein between Austria and Prussia postponed for a while the outbreak of war between the two powers. It was also here (August-September 1879) that Prince Bismarck negotiated with Count Julius Andrássy the Austro-German treaty, which resulted in the formation of the Triple Alliance.

See Pröll, _Gastein, Its Springs and Climate_ (Vienna, 5th ed., 1893).

GASTRIC ULCER (ulcer of the stomach), a disease of much gravity, commonest in females, and especially in anaemic domestic servants. It is connected in many instances with impairment of the circulation in the stomach and the formation of a clot in a small blood-vessel (thrombosis). It may be due to an impoverished state of the blood (anaemia), but it may also arise from disease of the blood-vessels, the result of long-continued indigestion and gastric catarrh.

When clotting takes place in a blood-vessel the nutrition of that limited area of the stomach is cut off, and the patch undergoes digestion by the unresisted action of the gastric juices, an ulcer being formed. The ulcer is usually of the size of a silver threepence or sixpence, round or oval, and, eating deeply, is apt to make a hole right through the coats of the stomach. Its usual site is upon the posterior wall of the upper curvature, near to the pyloric orifice. It may undergo a healing process at any stage, in which case it may leave but little trace of its existence; while, on the other hand, it may in the course of cicatrizing produce such an amount of contraction as to lead to stricture of the pylorus, or to a peculiar hour-glass deformity of the stomach. Perforation is in most cases quickly fatal, unless previously the stomach has become adherent to some neighbouring organ, by which the dangerous effects of this occurrence may be averted, or unless the condition has been promptly recognized and an operation has been quickly done. Usually there is but one ulcer, but sometimes there are several ulcers.

The symptoms of ulcer of the stomach are often indefinite and obscure, and in some cases the diagnosis has been first made on the occurrence of a fatal perforation. First among the symptoms is pain, which is present at all times, but is markedly increased after food. The pain is situated either at the lower end of the breast-bone or about the middle of the back. Sometimes it is felt in the sides. It is often extremely severe, and is usually accompanied with localized tenderness and also with a sense of oppression, and by an inability to wear tight clothing. The pain is due to the movements of the stomach set up by the presence of the food, as well as to the irritation of the inflamed nerve filaments in the floor of the ulcer. Vomiting is a usual symptom. It occurs either soon after the food is swallowed or at a later period, and generally relieves the pain and discomfort. Vomiting of blood (haematemesis) is a frequent and important symptom. The blood may show itself in the form of a brown or coffee-like mixture, or as pure blood of dark colour and containing clots. It comes from some vessel or vessels which the ulcerative process has ruptured. Blood is also found mixed with the discharges from the bowels, rendering them dark or tarry-looking. The general condition of the patient with gastric ulcer is, as a rule, that of extreme ill-health, with pallor, emaciation and debility. The tongue is red, and there is usually constipation. In most of the cases the disease is chronic, lasting for months or years; and in those cases where the ulcers are large or multiple, incomplete healing may take place, relapses occurring from time to time. But the ulcers may give rise to no marked symptoms, and there have been instances where fatal perforation suddenly took place, and where post-mortem examination revealed the existence of long-standing ulcers which had given rise to no suggestive symptoms. While gastric ulcer is to be regarded as dangerous, its termination, in the great majority of cases, is in recovery. It frequently, however, leaves the stomach in a delicate condition, necessitating the utmost care as regards diet. Occasionally the disease proves fatal by sudden haemorrhage, but a fatal result is more frequently due to perforation and the escape of the contents of the stomach into the peritoneal cavity, in which case death usually occurs in from twelve to forty-eight hours, either from shock or from peritonitis. Should the stomach become adherent to another organ, and fatal perforation be thus prevented, chronic "indigestion" may persist, owing to interference with the natural movements of the stomach. Stricture of the pylorus and consequent dilatation of the stomach may be caused by the cicatrization of an ulcer.

The patient should at once be sent to bed and kept there, and allowed for a while nothing stronger than milk and water or milk and lime water. But if bleeding has recently taken place no food whatever should be allowed by the stomach, and the feeding should be by nutrient enemata. As the symptoms quiet down, eggs may be given beaten up with milk, and later, bread and milk and home-made broths and soups. Thus the diet advances to chicken and vegetables rubbed through a sieve, to custard pudding and bread and butter. As regards medicines, iron is the most useful, but no pills of any sort should be given. Under the influence of rest and diet most gastric ulcers get well. The presence of healthy-looking scars upon the surface of the stomach, which are constantly found in operating upon the interior of the abdomen, or as revealed in post-mortem examinations, are evidence of the truth of this statement. It is unlikely that under the treatment just described perforation of the stomach will take place, and if the surgeon is called in to assist he will probably advise that operation is inadvisable. Moreover, he knows that if he should open the abdomen to search for an ulcer of the stomach he might fail to find it; more than that, his search might also be in vain if he opened the stomach itself and examined the interior. Serious haemorrhages, however, may make it necessary that a prompt and thorough search should be made in order that the surgeon may endeavour to locate the ulcer, and, having found it, secure the damaged vessel and save the patient from death by bleeding.

Perforation of a gastric ulcer having taken place, the septic germs, which were harmless whilst in the stomach, escape with the rest of the contents of the stomach into the general peritoneal cavity. The immediate effects of this leakage are sudden and severe pain in the upper part of the abdomen and a great shock to the system (collapse). The muscles of the abdominal wall become hard and resisting, and as peritonitis appears and the intestines are distended with gas, the abdomen is distended and becomes greatly increased in size and ceases to move, the respiratory movements being short and quick. At first, most likely, the temperature drops below normal, and the pulse quickens. Later, the temperature rises. If nothing is done, death from the septic poisoning of peritonitis is almost certain.

The treatment of ruptured gastric ulcer demands immediate operation. An incision should be made in the upper part of the middle line of the abdomen, and the perforation should be looked for. There is not, as a rule, much difficulty in finding it, as there are generally deposits of lymph near the spot, and other signs of local inflammation; moreover, the contents of the stomach may be seen escaping from the opening. The ulcer is to be closed by running a "purse-string" suture in the healthy tissue around it, and the place is then buried in the stomach by picking up small folds of the stomach-wall above and below it and fixing them together by suturing. This being done, the surface of the stomach, and the neighbouring viscera which have been soiled by the leakage, are wiped clean and the abdominal wound is closed, provision being made for efficient drainage. A large proportion of cases of perforated gastric ulcer thus treated recover. (E. O.*)

GASTRITIS (Gr. [Greek: gastêr], stomach), an inflammatory affection of the stomach, of which the condition of catarrh, or irritation of its mucous membrane, is the most frequent and most readily recognized. This may exist in an acute or a chronic form, and depends upon some condition, either local or general, which produces a congested state of the circulation in the walls of the stomach (see DIGESTIVE ORGANS: _Pathology_).

_Acute Gastritis_ may arise from various causes. The most intense forms of inflammation of the stomach are the toxic conditions which follow the swallowing of corrosive poisons, such as strong mineral acids of alkalis which may extensively destroy the mucous membrane. Other non-corrosive poisons cause acute degeneration of the stomach wall (see POISONS). Acute inflammatory conditions may be secondary to zymotic diseases such as diphtheria, pyaemia, typhus fever and others. Gastritis is also caused by the ingestion of food which has begun to decompose, or may result from eating unsuitable articles which themselves remain undigested and so excite acute catarrhal conditions. These give rise to the symptoms well known as characterizing an acute "bilious attack," consisting in loss of appetite, sickness or nausea, and headache, frontal or occipital, often accompanied with giddiness. The tongue is furred, the breath foetid, and there is pain or discomfort in the region of the stomach, with sour eructations, and frequently vomiting, first of food and then of bilious matter. An attack of this kind tends to subside in a few days, especially if the exciting cause be removed. Sometimes, however, the symptoms recur with such frequency as to lead to the more serious chronic form of the disease.

The treatment bears reference, in the first place, to any known source of irritation, which, if it exist, may be expelled by an emetic or purgative (except in cases due to poisoning). This, however, is seldom necessary, since vomiting is usually present. For the relief of sickness and pain the sucking of ice and counter-irritation over the region of the stomach are of service. Further, remedies which exercise a soothing effect upon an irritable mucous membrane, such as bismuth or weak alkaline fluids, and along with these the use of a light milk diet, are usually sufficient to remove the symptoms.

_Chronic Gastric Catarrh_ may result from the acute or may arise independently. It is not infrequently connected with antecedent disease in other organs, such as the lungs, heart, liver or kidneys, and it is especially common in persons addicted to alcoholic excess. In this form the texture of the stomach is more altered than in the acute form, except in the toxic and febrile forms above referred to. It is permanently in a state of congestion, and its mucous membrane and muscular coat undergo thickening and other changes, which markedly affect the function of digestion. The symptoms are those of dyspepsia in an aggravated form (see DYSPEPSIA), of which discomfort and pain after food, with distension and frequently vomiting, are the chief; and the treatment must be conducted in reference to the causes giving rise to it. The careful regulation of the diet, alike as to the amount, the quality, and the intervals between meals, demands special attention. Feeding on artificially soured milk may in many cases be useful. Lavage or washing out of the stomach with weak alkaline solutions has been used with marked success in the treatment of chronic gastritis. Of medicinal agents, bismuth, arsenic, nux vomica, and the mineral acids are all of acknowledged efficacy, as are also preparations of pepsin.

GASTROPODA, the second of the five classes of animals constituting the phylum Mollusca. For a discussion of the relationship of the Gastropoda to the remaining classes of the phylum, see MOLLUSCA.

The Gastropoda are mainly characterized by a loss of symmetry, produced by torsion of the visceral sac. This torsion may be resolved into two successive movements. The first is a ventral flexure in the antero-posterior or sagittal plane; the result of this is to approximate the two ends of the alimentary canal. In development, the openings of the mantle-cavity and the anus are always originally posterior; later they are brought forward ventrally. During this first movement flexure is also produced by the coiling of the visceral sac and shell; primitively the latter was bowl-shaped; but the ventral flexure, which brings together the two extremities of the digestive tube, gives the visceral sac the outline of a more or less acute cone. The shell necessarily takes this form also, and then becomes coiled in a dorsal or anterior plane--that is to say, it becomes exogastric. This condition may be seen in embryonic _Patellidae, Fissurellidae_ and _Trochidae_ (fig. 1, A), and agrees with the method of coiling of a mollusc without lateral torsion, such as _Nautilus_. But ultimately the coil becomes ventral or endogastric, in consequence of the second torsion movement then apparent.

The shell is represented as fixed, while the head and foot rotate from left to right. In reality the head and foot are fixed and the shell rotates from right to left.

The second movement is a lateral torsion of the visceral mass, the foot remaining a fixed point; this torsion occurs in a plane approximately at right angles to that of the first movement, and carries the pallial aperture and the anus from behind forwards. If, at this moment, the animal were placed with mouth and ventral surface turned towards the observer, this torsion carries the circumanal complex in a clockwise direction (along the right side in dextral forms) through 180° as compared with its primitive condition. The (primitively) right-hand organs of the complex thus become left-hand, and vice versa. The visceral commissure, while still surrounding the digestive tract, becomes looped; its right half, with its proper ganglion, passes to the left side over the dorsal face of the alimentary canal (whence the name supra-intestinal), while the left half passes below towards the right side, thus originating the name infra-intestinal given to this half and to its ganglion. Next, the shell, the coil of which was at first exogastric, being also included in this rotation through 180°, exhibits an endogastric coiling (fig. 1, B, C). This, however, is not generally retained in one plane, and the spire projects, little by little, on the side which was originally left, but finally becomes right (in dextral forms, with a clockwise direction, if viewed from the side of the spire; but counter-clockwise in sinistral forms). Finally, the original symmetry of the circumanal complex vanishes; the anus leaves the centre of the pallial cavity and passes towards the right side (left side in sinistral forms); the organs of this side become atrophied and disappear. The essential feature of the asymmetry of Gastropoda is the atrophy or disappearance of the primitively left half of the circumanal complex (the right half in sinistral forms), including the gill, the auricle, the osphradium, the hypobranchial gland and the kidney.

In dextral Gastropods the only structure found on the topographically right side of the rectum is the genital duct. But this is not part of the primitive complex. It is absent in the most primitive and symmetrical forms, such as _Haliotis_ and _Pleurotomaria_. Originally the gonads opened into the kidneys. In the most primitive existing Gastropods the gonad opens into the right kidney (_Patellidae, Trochidae, Fissurellidae_). The gonaduct, therefore, is derived from the topographically right kidney. The transformation has been actually shown to take place in the development of Paludina. In a dextral Gastropod the shell is coiled in a right-handed spiral from apex to mouth, and the spiral also projects to the right of the median plane of the animal.

When the shell is sinistral the asymmetry of the organs is usually reversed, and there is a complete situs _inversus viscerum_, the direction of the spiral of the shell corresponding to the position of the organs of the body. _Triforis, Physa, Clausilia_ are examples of sinistral Gastropods, but reversal also occurs as an individual variation among forms normally dextral. But there are forms in which the involution is "hyperstrophic," that is to say, the turns of the spire projecting but slightly, the spire, after flattening out gradually, finally becomes re-entrant and transformed into a false umbilicus; at the same time that part which corresponds to the umbilicus of forms with a normal coil projects and constitutes a false spire; the coil thus appears to be sinistral, although the asymmetry remains dextral, and the coil of the operculum (always the opposite to that of the shell) sinistral (e.g. _Lanistes_ among Streptoneura, _Limacinidae_ among Opisthobranchia). The same, _mutatis mutandis_, may occur in sinistral shells.

The problem of the causes of the torsion of the Gastropod body has been much discussed. E.R. Lankester in the ninth edition of this work attributed it to the pressure of the shell and visceral hump towards the right side. He referred also to the nautiloid shell of the larva falling to one side. But these are two distinct processes. In the larva a nautiloid shell is developed which is coiled exogastrically, that is, dorsally, and the pallial cavity is posterior or ventral (fig. 2, C): the larva therefore resembles _Nautilus_ in the relations of body and shell. The shell then rotates towards the left side through 180°, so that it becomes ventral or endogastric (fig. 2, D). The pallial cavity, with its organs, is by this torsion moved up the _right_ side of the larva to the dorsal surface, and thus the left organs become right and vice versa. In the subsequent growth of the shell the spire comes to project on the right side, which was originally the left. Neither the rotation of the shell as a whole nor its helicoid spiral coiling is the immediate cause of the torsion of the body in the individual, for the direction of the torsion is indicated in the segmentation of the ovum, in which there is a complete reversal of the cleavage planes in sinistral as compared with dextral forms. The facts, however, strongly suggest that the original cause of the torsion was the weight of the exogastric shell and visceral hump, which in an animal creeping on its ventral surface necessarily fell over to one side. It is not certain that the projection of the spire to the originally left side of the shell has anything to do with the falling over of the shell to that side. The facts do not support such a suggestion. In the larva there is no projection at the time the torsion takes place. In some forms the coiling disappears in the adult, leaving the shell simply conical as in _Patellidae, Fissurellidae_, &c., and in some cases the shell is coiled in one plane, e.g. _Planorbis_. In all these cases the torsion and asymmetry of the body are unaffected.

The characteristic torsion attains its maximum effect among the majority of the Streptoneura. It is followed in some specialized Heteropoda and in the Euthyneura by a torsion in the opposite direction, or detorsion, which brings the anus farther back and untwists the visceral commissure (see Euthyneura, below). This conclusion has shown that the Euthyneura do not represent an archaic form of Gastropoda, but are themselves derived from streptoneurous forms. The difference between the two sub-classes has been shown to be slight; certain of the more archaic Tectibranchia (_Actaeon_) and Pulmonata (_Chilina_) still have the visceral commissure long and not untwisted. The fact that all the Euthyneura are hermaphrodite is not a fundamental difference; several Streptoneura are so, likewise _Valvata, Oncidiopsis, Marsenina, Odostomia, Bathysciadium, Entoconcha_.

_Classification._--The class Gastropoda is subdivided as follows:

Sub-class I. Streptoneura. Order 1. Aspidobranchia. Sub-order 1. Docoglossa. " 2. Rhipidoglossa. Order 2. Pectinibranchia. Sub-order 1. Taenioglossa. Tribe 1. Platypoda. " 2. Heteropoda. Sub-order 2. Stenoglossa. Tribe 1. Rachiglossa. " 2. Toxiglossa.

Sub-class II. Euthyneura. Order 1. Opisthobranchia. Sub-order 1. Tectibranchia. Tribe 1. Bullomorpha. " 2. Aplysiomorpha. " 3. Pleurobranchomorpha. Sub-order 2. Nudibranchia. Tribe 1. Tritoniomorpha. " 2. Doridomorpha. " 3. Eolidomorpha. " 4. Elysiomorpha. Order 2. Pulmonata. Sub-order 1. Basommatophora. " 2. Stylommatophora. Tribe 1. Holognatha. " 2. Agnatha. " 3. Elasmognatha. " 4. Ditremata.

Sub-Class I.--STREPTONEURA

In this division the torsion of the visceral mass and visceral commissure is at its maximum, the latter being twisted into a figure of eight. The right half of the commissure with its ganglion is supra-intestinal, the left half with its ganglion infra-intestinal. In some cases each pleural ganglion is connected with the opposite branch of the visceral commissure by anastomosis with the pallial nerve, a condition which is called dialyneury; or there may be a direct connective from the pleural ganglion to the visceral ganglion of the opposite side, which is called zygoneury. The head bears only one pair of tentacles. The radular teeth are of several different kinds in each transverse row. The heart is usually posterior to the branchia (proso-branchiate). The sexes are usually separate.

The old division into Zygobranchia and Azygobranchia must be abandoned, for the Azygobranchiate Rhipidoglossa have much greater affinity to the Zygobranchiate _Haliotidae_ and _Fissurellidae_ than to the Azygobranchia in general. This is shown by the labial commissure and pedal cords of the nervous system, by the opening of the gonad into the right kidney, and by other points. Further, the _Pleurotomariidae_ have been discovered to possess two branchiae. The sub-class is now divided into two orders: the Aspidobranchia in which the branchia or ctenidium is bipectinate and attached only at its base, and the Pectinibranchia in which the ctenidium is monopectinate and attached to the mantle throughout its length.

Order I. ASPIDOBRANCHIA.--These are the most primitive Gastropods, retaining to a great degree the original symmetry of the organs of the pallial complex, having two kidneys, in some cases two branchiae, and two auricles. The gonad has no accessory organs and except in _Neritidae_ no duct, but discharges into the right kidney.

Forms adapted to terrestrial life and to aerial respiration occur in various divisions of Gastropods, and do not constitute a single homogeneous group. Thus the _Helicinidae_, which are terrestrial, are now placed among the Aspidobranchia. In these there are neither branchia nor osphradium, and the pallial chamber which retains its large opening serves as a lung. Degeneration of the shell occurs in some members of the order. It is largely covered by the mantle in some _Fissurellidae_, is entirely internal in _Pupilia_ and absent in _Titiscaniidae_.

The common limpet is a specially interesting and abundant example of the more primitive Aspidobranchia. The foot of the limpet is a nearly circular disk of muscular tissue; in front, projecting from and raised above it, are the head and neck (figs. 4, 13). The visceral hump forms a low conical dome above the sub-circular foot, and standing out all round the base of this dome so as completely to overlap the head and foot, is the circular mantle-skirt. The depth of free mantle-skirt is greatest in front, where the head and neck are covered in by it. Upon the surface of the visceral dome, and extending to the edge of the free mantle-skirt, is the conical shell. When the shell is taken away (best effected by immersion in hot water) the surface of the visceral dome is found to be covered by a black-coloured epithelium, which may be removed, enabling the observer to note the position of some organs lying below the transparent integument (fig. 5). The muscular columns (c) attaching the foot to the shell form a ring incomplete in front, external to which is the free mantle-skirt. The limits of the large area formed by the flap over the head and neck (ecr) can be traced, and we note the anal papilla showing through and opening on the right shoulder, so to speak, of the animal into the large anterior region of the sub-pallial space. Close to this the small renal organ (i, mediad) and the larger renal organ (k, to the right and posteriorly) are seen, also the pericardium (l) and a coil of the intestine (int) embedded in the compact liver.

On cutting away the anterior part of the mantle-skirt so as to expose the sub-pallial chamber in the region of the neck, we find the right and left renal papillae (discovered by Lankester in 1867) on either side of the anal papilla (fig. 6), but no gills. If a similar examination be made of the allied genus _Fissurella_ (fig. 17, d), we find right and left of the two renal apertures a right and left gill-plume or ctenidium, which here as in _Haliotis_ and _Pleurotomaria_ retain their original paired condition. In _Patella_ no such plumes exist, but right and left of the neck are seen a pair of minute oblong yellow bodies (fig. 6, d), which were originally described by Lankester as orifices possibly connected with the evacuation of the generative products. On account of their position they were termed by him the "capito-pedal orifices," being placed near the junction of head and foot. J.W. Spengel has, however, in a most ingenious way shown that these bodies are the representatives of the typical pair of ctenidia, here reduced to a mere rudiment. Near to each rudimentary ctenidium Spengel has discovered an olfactory patch or osphradium (consisting of modified epithelium) and an olfactory nerve-ganglion (fig. 8). It will be remembered that, according to Spengel, the osphradium of mollusca is definitely and intimately related to the gill-plume or ctenidium, being always placed near the base of that organ; further, Spengel has shown that the nerve-supply of this olfactory organ is always derived from the visceral loop. Accordingly, the nerve-supply affords a means of testing the conclusion that we have in Lankester's capito-pedal bodies the rudimentary ctenidia. The accompanying diagrams (figs. 9, 10) of the nervous systems of _Patella_ and of _Haliotis_, as determined by Spengel, show the identity in the origin of the nerves passing from the visceral loop to Spengel's olfactory ganglion of the Limpet, and that of the nerves which pass from the visceral loop of _Haliotis_ to the olfactory patch or osphradium, which lies in immediate relation on the right and on the left side to the right and left gill-plumes (ctenidia) respectively. The same diagrams serve to demonstrate the streptoneurous condition of the visceral loop in Aspidobranchia.

Thus, then, we find that the limpet possesses a symmetrically disposed pair of ctenidia in a rudimentary condition, and justifies its position among Aspidobranchia. At the same time it possesses a totally distinct series of _functional_ gills, which are not derived from the modification of the typical molluscan ctenidium. These gills are in the form of delicate lamellae (fig. 4, f), which form a series extending completely round the inner face of the depending mantle-skirt. This circlet of gill-lamellae led Cuvier to class the limpets as Cyclobranchiata, and, by erroneous identification of them with the series of metamerically repeated ctenidia of _Chiton_, to associate the latter mollusc with the former. The gill-lamellae of _Patella_ are processes of the mantle comparable with the plait-like folds often observed on the roof of the branchial chamber in other Gastropoda (e.g. _Buccinum_ and _Haliotis_). They are termed pallial gills. The only other molluscs in which they are exactly represented are the curious Opisthobranchs _Phyllidia_ and _Pleurophyllidia_ (fig. 55). In these, as in _Patella_, the typical ctenidia are aborted, and the branchial function is assumed by close-set lamelliform processes arranged in a series beneath the mantle-skirt on either side of the foot. In fig. 4, d, the large branchial vein of _Patella_ bringing blood from the gill-series to the heart is seen; where it crosses the series of lamellae there is a short interval devoid of lamellae.

The heart in _Patella_ consists of a single auricle (not two as in _Haliotis_ and _Fissurella_) and a ventricle; the former receives the blood from the branchial vein, the latter distributes it through a large aorta which soon leads into irregular blood-lacunae.

The existence of two renal organs in _Patella_, and their relation to the pericardium (a portion of the coelom), is important. Each renal organ is a sac lined with glandular epithelium (ciliated cell, with concretions) communicating with the exterior by its papilla, and by a narrow passage with the pericardium. The connexion with the pericardium of the smaller of the two renal organs was demonstrated by Lankester in 1867, at a time when the fact that the renal organ of the Mollusca, as a rule, opens into the pericardium, and is therefore a typical nephridium, was not known. Subsequent investigations carried on under the direction of the same naturalist have shown that the larger as well as the smaller renal sac is in communication with the pericardium. The walls of the renal sacs are deeply plaited and thrown into ridges. Below the surface these walls are excavated with blood-vessels, so that the sac is practically a series of blood-vessels covered with renal epithelium, and forming a meshwork within a space communicating with the exterior. The larger renal sac (remarkably enough, that which is aborted in other Anisopleura) extends between the liver and the integument of the visceral dome very widely. It also bends round the liver as shown in fig. 12, and forms a large sac on half of the upper surface of the muscular mass of the foot. Here it lies close upon the genital body (ovary or testis), and in such intimate relationship with it that, when ripe, the gonad bursts into the renal sac, and its products are carried to the exterior by the papilla on the right side of the anus (Robin, Dall). This fact led Cuvier erroneously to the belief that a duct existed leading from the gonad to this papilla. The position of the gonad, best seen in the diagrammatic section (fig. 13), is, as in other Aspidobranchia, devoid of a special duct communicating with the exterior. This condition, probably an archaic one, distinguishes the Aspidobranchia from other Gastropoda.

The digestive tract of _Patella_ offers some interesting features. The odontophore is powerfully developed; the radular sac is extraordinarily long, lying coiled in a space between the mass of the liver and the muscular foot. The radula has 160 rows of teeth with twelve teeth in each row. Two pairs of salivary ducts, each leading from a salivary gland, open into the buccal chamber. The oesophagus leads into a remarkable stomach, plaited like the manyplies of a sheep, and after this the intestine takes a very large number of turns embedded in the yellow liver, until at last it passes between the two renal sacs to the anal papilla. A curious ridge (spiral? valve) which secretes a slimy cord is found upon the inner wall of the intestine. The general structure of the Molluscan intestine has not been sufficiently investigated to render any comparison of this structure of _Patella_ with that of other Mollusca possible. The eyes of the limpet deserve mention as examples of the most primitive kind of eye in the Molluscan series. They are found one on each cephalic tentacle, and are simply minute open pits or depressions of the epidermis, the epidermic cells lining them being pigmented and connected with nerves (compare fig. 14, art. CEPHALOPODA). The limpet breeds upon the southern English coast in the early part of April, but its development has not been followed. It has simply been traced as far as the formation of a diblastula which acquires a ciliated band, and becomes a nearly spherical trochosphere. It is probable that the limpet takes several years to attain full growth, and during that period it frequents the same spot, which becomes gradually sunk below the surrounding surface, especially if the rock be carbonate of lime. At low tide the limpet (being a strictly intertidal organism) is exposed to the air, and (according to trustworthy observers) quits its attachment and walks away in search of food (minute encrusting algae), and then once more returns to the identical spot, not an inch in diameter, which belongs, as it were, to it. Several million limpets--twelve million in Berwickshire alone--are annually used on the east coast of Britain as bait.

Sub-order 1. _Docoglossa._--Nervous system without dialyneury. Eyes are open invaginations without crystalline lens. Two osphradia present but no hypobranchial glands nor operculum. Teeth of radula beam-like, and at most three marginal teeth on each side. Heart has only a single auricle, neither heart nor pericardium traversed by rectum. Shell conical without spire.

Fam. 1.--_Acmaeidae._ A single bipectinate ctenidium on left side. Acmaea, without pallial branchiae, British. Scurria, with pallial branchiae in a circle beneath the mantle.

Fam. 2.--_Tryblidiidae._ Muscle scar divided into numerous impressions. _Tryblidium_, Silurian.

Fam. 3.--_Patellidae_. No ctenidia but pallial branchiae in a circle between mantle and foot. _Patella_, pallial branchiae forming a complete circle, no epipodial tentacles, British. _Ancistromesus_, radula with median central tooth. _Nacella_, epipodial tentacles present. _Helcion_, circlet of branchiae interrupted anteriorly, British.

Fam. 4.--_Lepetidae._ Neither ctenidia nor pallial branchiae. _Lepeta_, without eyes. _Pilidium. Propilidium._

Fam. 5.--_Bathysciadidae._ Hermaphrodite; head with appendage on right side; radula without central tooth. _Bathysciadium_, abyssal.

Sub-order 2. RHIPIDOGLOSSA.--Aspidobranchia with a palliovisceral anastomosis (dialyneurous); eye-vesicle closed, with crystalline lens; ctenidia, osphradia and hypobranchial glands paired or single. Radula with very numerous marginal teeth arranged like the rays of a fan. Heart with two auricles; ventricle traversed by the rectum, except in the _Helicinidae_. An epipodial ridge on each side of the foot and cephalic expansions between the tentacles often present.

Fam. 1.--_Pleurotomariidae_. Shell spiral; mantle and shell with an anterior fissure; two ctenidia; a horny operculum. _Pleurotomaria_, epipodium without tentacles. Genus includes several hundred extinct species ranging from the Silurian to the Tertiary. Five living species from the Antilles, Japan and the Moluccas. Moluccan species is 19 cm. in height.

Fam. 2.--_Bellerophontidae._ 300 species, all fossil, from Cambrian to Trias.

Fam. 3.--_Euomphalidae._ Also extinct, from Cambrian to Cretaceous.

Fam. 4.--_Haliotidae._ Spire of shell much reduced; two bipectinate ctenidia, the right being the smaller; no operculum. Haliotis.

Fam. 5.--_Velainiellidae_, an extinct family from the Eocene.

Fam. 6.--_Fissurellidae._ Shell conical; slit or hole in anterior part of mantle; two symmetrical ctenidia; no operculum. _Emarginula_, mantle and shell with a slit, British. _Scutum_, mantle split anteriorly and reflected over shell, which has no slit. _Puncturella_, mantle and shell with a foramen in front of the apex, British. _Fissurella_, mantle and shell perforated at apex, British.

Fam. 7.--_Cocculinidae._ Shell conical, symmetrical, without slit or perforation. _Cocculina_, abyssal.

Fam. 8.--_Trochidae._ Shell spirally coiled; a single ctenidium; eyes perforated; a horny operculum; lobes between the tentacles. _Trochus_, shell umbilicated, spire pointed and prominent, British. _Monodonta_, no jaws, spire not prominent, no umbilicus, columella toothed. _Gibbula_, with jaws, three pairs of epipodial cirri without pigment spots at their bases, British. _Margarita_, five to seven pairs of epipodial cirri with a pigment spot at base of each.

Fam. 9.--_Stomatellidae._ Spire of shell much reduced; a single ctenidium. _Stomatella_, foot truncated posteriorly, an operculum present, no epipodial tentacles. _Gena_, foot elongated posteriorly, no operculum.

Fam. 10.--_Delphinulidae._ Shell spirally coiled; operculum horny; intertentacular lobes absent. _Delphinula._

Fam. 11.--_Liotiidae_, shell globular, margin of aperture thickened. _Liotia_.

Fam. 12.--_Cyclostrematidae._ Shell flattened, umbilicated; foot anteriorly truncated with angles produced into lobes. _Cyclostrema._ _Teinostoma._

Fam. 13.--_Trochonematidae._ All extinct, Cambrian to Cretaceous.

Fam. 14.--_Turbinidae._ Shell spirally coiled; epipodial tentacles present; operculum thick and calcareous. _Turbo. Astralium. Molleria. Cyclonema._

Fam. 15.--_Phasianellidae._ Shell not nacreous, without umbilicus, with prominent spire and polished surface. _Phasianella._

Fam. 16.--_Umboniidae._ Shell flattened, not umbilicated, generally smooth; operculum horny. _Umbonium. Isanda._

Fam. 17.--_Neritopsidae._ Shell semi-globular, with short spire; operculum calcareous, not spiral. _Neritopsis. Naticopsis_, extinct.

Fam. 18.--_Macluritidae._ Extinct, Cambrian and Silurian.

Fam. 19.--_Neritidae._ Shell with very low spire, without umbilicus, internal partitions frequently absorbed; a single ctenidium; a cephalic penis present. _Nerita_, marine. _Neritina_, freshwater, British. _Septaria_, shell boat-shaped.

Fam. 20.--_Titiscaniidae._ Without shell and operculum, but with pallial cavity and ctenidium. _Titiscania_, Pacific.

Fam. 21.--_Helicinidae._ No ctenidium, but a pulmonary cavity; heart with a single auricle, not traversed by the rectum. _Helicina. Eutrochatella. Stoastoma. Bourceria._

Fam. 22.--_Hydrocenidae._ No ctenidium, but a pulmonary cavity; operculum with an apophysis. _Hydrocena_, Dalmatia.

Fam. 23.--_Proserpinidae._ No operculum. _Proserpina_, Central America.

Order 2. PECTINIBRANCHIA.--In this order there is no longer any trace of bilateral symmetry in the circulatory, respiratory and excretory organs, the topographically right half of the pallial complex having completely disappeared, except the right kidney, which is represented by the genital duct. There is usually a penis in the male. The ctenidium is monopectinate and attached to the mantle along its whole length, except in _Adeorbis_ and _Valvata_; in the latter alone it is bipectinate. There is a single well-developed, often pectinated osphradium. The eye is always a closed vesicle, and the internal cornea is extensive. In the radula there is a single central tooth or none.

The former classification into Holochlamyda, Pneumochlamyda and Siphonochlamyda has been abandoned, as it was founded on adaptive characters not always indicative of true affinities. The order is now divided into two sub-orders: the Taenioglossa, in which there are three teeth on each side of the median tooth of the radula, and the Stenoglossa, in which there is only one tooth on each side of the median tooth. In the latter a pallial siphon, a well-developed proboscis and an unpaired oesophageal gland are always present, in the former they are usually absent. The siphon is an incompletely tubular outgrowth of the mantle margin on the left side, contained in a corresponding outgrowth of the edge of the shell-mouth, and serving to conduct water to the respiratory cavity.

The condition usually spoken of as a "proboscis" appears to be derived from the condition of a simple rostrum (having the mouth at its extremity) by the process of _incomplete introversion_ of that simple rostrum. There is no reason in the actual significance of the word why the term "proboscis" should be applied to an alternately introversible and eversible tube connected with an animal's body, and yet such is a very customary use of the term. The introversible tube may be completely closed, as in the "proboscis" of Nemertine worms, or it may have a passage in it leading into a non-eversible oesophagus, as in the present case, and in the case of the eversible pharynx of the predatory Chaetopod worms. The diagrams here introduced (fig. 19) are intended to show certain important distinctions which obtain amongst the various "introverts," or intro- and e-versible tubes so frequently met with in animal bodies. Supposing the tube to be completely introverted and to commence its eversion, we then find that eversion may take place, either by a forward movement of the side of the tube near its attached base, as in the proboscis of the Nemertine worms, the pharynx of Chaetopods and the eye-tentacle of Gastropods, or by a forward movement of the inverted apex of the tube, as in the proboscis of the Rhabdocoel Planarians, and in that of Gastropods here under consideration. The former case we call "pleurecbolic" (fig. 19, A, B, C, H, I, K), the latter "acrecbolic" tubes or introverts (fig. 19, D, E, F, G). It is clear that, if we start from the condition of full eversion of the tube and watch the process of introversion, we shall find that the pleurecbolic variety is introverted by the apex of the tube sinking inwards; it may be called acrembolic, whilst conversely the acrecbolic tubes are pleurembolic. Further, it is obvious enough that the process either of introversion or of eversion of the tube may be arrested at any point, by the development of fibres connecting the wall of the introverted tube with the wall of the body, or with an axial structure such as the oesophagus; on the other hand, the range of movement of the tubular introvert may be unlimited or complete. The acrembolic proboscis or frontal introvert of the Nemertine worms has a complete range. So has the acrembolic pharynx of Chaetopods, if we consider the organ as terminating at that point where the jaws are placed and the oesophagus commences. So too the acrembolic eye-tentacle of the snail has a complete range of movement, and also the pleurembolic proboscis of the Rhabdocoel prostoma. The introverted rostrum of the Pectinibranch Gastropods presents in contrast to these a limited range of movement. The "introvert" in these Gastropods is not the pharynx as in the Chaetopod worms, but a prae-oral structure, its apical limit being formed by the true lips and jaws, whilst the apical limit of the Chaetopod's introvert is formed by the jaws placed at the junction of pharynx and oesophagus, so that the Chaetopod's introvert is part of the stomodaeum or fore-gut, whilst that of the Gastropod is external to the alimentary canal altogether, being in front of the mouth, not behind it, as is the Chaetopod's. Further, the Gastropod's introvert is pleurembolic (and therefore acrecbolic), and is limited both in eversion and in introversion; it cannot be completely everted owing to the muscular bands (fig. 19, G), nor can it be fully introverted owing to the bands (fig. 19, F) which tie the axial pharynx to the adjacent wall of the apical part of the introvert. As in all such intro- and e-versible organs, eversion of the Gastropod proboscis is effected by pressure communicated by the muscular body-wall to the liquid contents (blood) of the body-space, accompanied by the relaxation of the muscles which directly pull upon either the sides or the apex of the tubular organ. The inversion of the proboscis is effected directly by the contraction of these muscles. In various members of the Pectinibranchia the mouth-bearing cylinder is introversible (i.e. is a _proboscis_)--with rare exceptions these forms have a siphonate mantle-skirt. On the other hand, many which have a siphonate mantle-skirt are not provided with an introversible mouth-bearing cylinder, but have a simple non-introversible rostrum, as it has been termed, which is also the condition presented by the mouth-bearing region in nearly all other Gastropoda. One of the best examples of the introversible mouth-cylinder or proboscis which can be found is that of the common whelk (_Buccinum undatum_) and its immediate allies. In fig. 23 the proboscis is seen in an everted state; it is only so carried when feeding, being withdrawn when the animal is at rest. Probably its use is to enable the animal to introduce its rasping and licking apparatus into very narrow apertures for the purposes of feeding, e.g. into a small hole bored in the shell of another mollusc.

The very large assemblage of forms coming under this order comprises the most highly developed predaceous sea-snails, numerous vegetarian species, a considerable number of freshwater and some terrestrial forms. The partial dissection of a male specimen of the common periwinkle, _Littorina littoralis_, drawn in fig. 20, will serve to exhibit the disposition of viscera which prevails in the group. The branchial chamber formed by the mantle-skirt overhanging the head has been exposed by cutting along a line extending backward from the letters vd to the base of the columella muscle mc, and the whole roof of the chamber thus detached from the right side of the animal's neck has been thrown over to the left, showing the organs which lie upon the roof. No opening into the body-cavity has been made; the organs which lie in the coiled visceral hump show through its transparent walls. The head is seen in front resting on the foot and carrying a median non-retractile snout or rostrum, and a pair of cephalic tentacles at the base of each of which is an eye. In many Gastropoda the eyes are not thus sessile but raised upon special eye-tentacles (figs. 25, 56). To the right of the head is seen the muscular penis p, close to the termination of the vas deferens (spermatic duct) vd. The testis t occupies a median position in the coiled visceral mass. Behind the penis on the same side is the hook-like columella muscle, a development of the retractor muscle of the foot, which clings to the spiral column or columella of the shell (see fig. 33). This columella muscle is the same thing as the muscles adhering to the shell in _Patella_, and the posterior adductor of Lamellibranchs.

The surface of the neck is covered by integument forming the floor of the branchial cavity. It has not been cut into. Of the organs lying on the reflected mantle-skirt, that which in the natural state lay nearest to the vas deferens on the right side of the median line of the roof of the branchial chamber is the rectum i', ending in the anus a. It can be traced back to the intestine i near the surface of the visceral hump, and it is found that the apex of the coil formed by the hump is occupied by the liver h and the stomach v. Pharynx and oesophagus are concealed in the head. The enlarged glandular structure of the walls of the rectum is frequent in the Pectinibranchia, as is also though not universal the gland marked y, next to the rectum. It is the adrectal gland, and in the genera _Murex_ and _Purpura_ secretes a colourless liquid which turns purple upon exposure to the atmosphere, and was used by the ancients as a dye. Near this and less advanced into the branchial chamber is the single renal organ or nephridium r with its opening to the exterior r'. Internally this glandular sac presents a second slit or aperture which leads into the pericardium (as is now found to be the case in all Mollusca). The heart c lying in the pericardium is seen in close proximity to the renal organ, and consists of a single auricle receiving blood from the gill, and of a single ventricle which pumps it through the body by an anterior and posterior aorta. The surface x of the mantle between the rectum and the gill-plume is thrown into folds which in many sea-snails (whelks or _Buccinidae_, &c.) are very strongly developed. The whole of this surface appears to be active in the secretion of a mucous-like substance. The single gill-plume br lies to the left of the median line in natural position. It corresponds to the right of the two primitive ctenidia in the untwisted archaic condition of the molluscan body, and does not project freely into the branchial cavity, but its axis is attached (by concrescence) to the mantle-skirt (roof of the branchial chamber). It is rare for the gill-plume of a Pectinibranch Gastropod to stand out freely as a plume, but occasionally this more archaic condition is exhibited as in _Valvata_ (fig. 30). Next beyond (to the left of) the gill-plume we find the so-called parabranchia, which is here simple, but sometimes lamellated as in _Purpura_ (fig. 22). This organ has, without reason, been supposed to represent the second ctenidium of the typical mollusc, which it cannot do on account of its position. It should be to the right of the anus were this the case. Spengel showed that the parabranchia of Gastropods is the typical olfactory organ or osphradium in a highly developed condition. The minute structure of the epithelium which clothes it, as well as the origin of the nerve which is distributed to the parabranchia, proves it to be the same organ which is found universally in molluscs at the base of each gill-plume, and tests the indrawn current of water by the sense of smell. The nerve to this organ is given off from the superior (original right, see fig. 3) visceral ganglion.

The figures which are given here of various Pectinibranchia are in most cases sufficiently explained by the references attached to them. As an excellent general type of the nervous system, attention may be directed to that of _Paludina_ drawn in fig. 21. On the whole the ganglia are strongly individualized in the Pectinibranchia, nerve-cell tissue being concentrated in the ganglia and absent from the cords. At the same time, the junction of the visceral loop above the intestine prevents in all Streptoneura the shortening of the visceral loop, and it is rare to find a fusion of the visceral ganglia with either pleural, pedal or cerebral--a fusion which can and does take place where the visceral loop is not above but below the intestine, e.g. in the Euthyneura (fig. 48), Cephalopoda and Lamellibranchia. As contrasted with the Aspidobranchia, we find that in the Pectinibranchia the pedal nerves are distinctly nerves given off from the pedal ganglia, rather than cord-like nerve-tracts containing both nerve-cells or ganglionic elements and nerve-fibres. Yet in some Pectinibranchia (_Paludina_) a ladder-like arrangement of the two pedal nerves and their lateral branches has been detected. The histology of the nervous system of Mollusca has yet to be seriously inquired into.

The alimentary canal of the Pectinibranchia presents little diversity of character, except in so far as the buccal region is concerned. Salivary glands are present, and in some carnivorous forms (_Dolium_) these secrete free sulphuric acid (as much as 2% is present in the secretion), which assists the animal in boring holes by means of its rasping tongue through the shells of other molluscs upon which it preys. A crop-like dilatation of the gut and a recurved intestine, embedded in the compact yellowish-brown liver, the ducts of which open into it, form the rest of the digestive tract and occupy a large bulk of the visceral hump. The buccal region presents a pair of shelly jaws placed laterally upon the lips, and a wide range of variation in the form of the denticles of the lingual ribbon or radula.

Well-developed glandular invaginations occur in different positions on the foot in Pectinibranchia. The most important of these opens by the ventral pedal pore, situated in the median line in the anterior half of the foot. This organ is probably homologous with the byssogenous gland of Lamellibranchs. The aperture, which was formerly supposed to be an aquiferous pore, leads into an extensive and often ramified cavity surrounded by glandular tubules. The gland has been found in both sub-orders of the Pectinibranchia, in _Cyclostoma_ and _Cypraea_ among the Taenioglossa, in _Hemifusus, Cassis, Nassa, Murex, Fasciolariidae, Turbinellidae, Olividae, Marginellidae_ and _Conidae_ among the Stenoglossa. It was discovered by J.T. Cunningham that in _Buccinum_ the egg-capsules are formed by this pedal gland and not by any accessory organ of the generative system. Such horny egg-capsules doubtless have the same origin in all other species in which they occur, e.g. _Fusus, Pyrula, Purpura, Murex, Nassa, Trophon, Voluta_, &c. The float of the pelagic _Janthina_, to which the egg-capsules are attached, probably is also formed by the secretion of the pedal gland.

Other glands opening on or near the foot are: (1) The suprapedal gland opening in the middle line between the snout and the anterior border of the foot. It is most commonly found in sessile forms and in terrestrial genera such as _Cyclostoma_; (2) the anterior pedal gland opening into the anterior groove of the foot, generally present in aquatic species; (3) dorsal posterior mucous glands in certain _Cyclostomatidae_.

The foot of the Pectinibranchia, unlike the simple muscular disk of the Isopleura and Aspidobranchia, is very often divided into lobes, a fore, middle and hind lobe (pro-, meso- and meta-podium, see figs. 24 and 25). Very usually, but not universally, the metapodium carries an operculum. The division of the foot into lobes is a simple case of that much greater elaboration or breaking up into processes and regions which it undergoes in the class Cephalopoda. Even among some Gastropoda (viz. the Opisthobranchia) we find the lobation of the foot still further carried out by the development of lateral lobes, the parapodia, whilst there are many Pectinibranchia, on the other hand, in which the foot has a simple oblong form without any trace of lobes.

The development of the Pectinibranchia has been followed in several examples, e.g. _Paludina, Purpura, Nassa, Vermetus, Neritina_. As in other Molluscan groups, we find a wide variation in the early process of the formation of the first embryonic cells, and their arrangement as a diblastula, dependent on the greater or less amount of food-yolk which is present in the egg-cell when it commences its embryonic changes. In fig. 26 the early stages of _Paludina vivipara_ are represented. There is but very little food-material in the egg of this Pectinibranch, and consequently the diblastula forms by invagination; the blastopore or orifice of invagination coincides with the anus, and never closes entirely. A well-marked trochosphere is formed by the development of an equatorial ciliated band; and subsequently, by the disproportionate growth of the lower hemisphere, the trochosphere becomes a veliger. The primitive shell-sac or shell-gland is well marked at this stage, and the pharynx is seen as a new ingrowth (the stomodaeum), about to fuse with and open into the primitively invaginated arch-enteron (fig. 26, F).

In other Pectinibranchia (and such variations are representative for all Mollusca, and not characteristic only of Pectinibranchia) we find that there is a very unequal division of the egg-cell at the commencement of embryonic development, as in _Nassa_. Consequently there is, strictly speaking, no invagination (emboly), but an overgrowth (epiboly) of the smaller cells to enclose the larger. The general features of this process and of the relation of the blastopore to mouth and anus have been explained in treating of the development of Mollusca generally. In such cases the blastopore may entirely close, and both mouth and anus develop as new ingrowths (stomodaeum and proctodaeum), whilst, according to the observations of N. Bobretzky, the closed blastopore may coincide in position with the mouth in some instances (_Nassa_, &c.), instead of with the anus. But in these epibolic forms, just as in the embolic _Paludina_, the embryo proceeds to develop its ciliated band and shell-gland, passing through the earlier condition of a trochosphere to that of the veliger. In the veliger stage many Pectinibranchia (_Purpura, Nassa_, &c.) exhibit, in the dorsal region behind the head, a contractile area of the body-wall. This acts as a larval heart, but ceases to pulsate after a time. Similar rhythmically contractile areas are found on the foot of the embryo Pulmonate _Limax_ and on the yolk-sac (distended foot-surface) of the Cephalopod _Loligo_. The preconchylian invagination or shell-gland is formed in the embryo behind the velum, on the surface opposite the blastopore. It is surrounded by a ridge of cells which gradually extends over the visceral sac and secretes the shell. In forms which are naked in the adult state, the shell falls off soon after the reduction of the velum, but in _Cenia, Runcina_ and _Vaginula_ the shell-gland and shell are not developed, and the young animal when hatched has already the naked form of the adult.

One further feature of the development of the Pectinibranchia deserves special mention. Many Gastropoda deposit their eggs, after fertilization, enclosed in capsules; others, as _Paludina_, are viviparous; others, again, as the Zygobranchia, agree with the Lamellibranch Conchifera (the bivalves) in having simple exits for the ova without glandular walls, and therefore discharge their eggs unenclosed in capsules freely into the sea-water; such unencapsuled eggs are merely enclosed each in its own delicate chorion. When egg-capsules are formed they are often of large size, have tough walls, and in each capsule are several eggs floating in a viscid fluid. In some cases all the eggs in a capsule develop; in other cases one egg only in a capsule (_Neritina_), or a small proportion (_Purpura, Buccinum_), advance in development; the rest are arrested either after the first process of cell-division (cleavage) or before that process. The arrested embryos or eggs are then swallowed and digested by those in the same capsule which have advanced in development. This is clearly the same process in essence as that of the formation of a vitellogenous gland from part of the primitive ovary, or of the feeding of an ovarian egg by the absorption of neighbouring potential eggs; but here the period at which the sacrifice of one egg to another takes place is somewhat late. What it is that determines the arrest of some eggs and the progressive development of others in the same capsule is at present unknown.

In the tribe of Pectinibranchia called Heteropoda the foot takes the form of a swimming organ. The nervous system and sense organs are highly developed. The odontophore also is remarkably developed, its lateral teeth being mobile, and it serves as an efficient organ for attacking the other pelagic forms on which the Heteropoda prey. The sexes are distinct, as in all Streptoneura; and genital ducts and accessory glands and pouches are present, as in all Pectinibranchia. The Heteropoda exhibit a series of modifications in the form and proportions of the visceral mass and foot, leading from a condition readily comparable with that of a typical Pectinibranch such as _Rostellaria_, with the three regions of the foot strongly marked and a coiled visceral hump of the usual proportions, up to a condition in which the whole body is of a tapering cylindrical shape, the foot a plate-like vertical fin, and the visceral hump almost completely atrophied. Three steps of this modification may be distinguished as three families:--_Atlantidae, Carinariidae_ and _Pterotrachaeidae_. They are true Pectinibranchia which have taken to a pelagic life, and the peculiarities of structure which they exhibit are strictly adaptations consequent upon their changed mode of life. Such adaptations are the transparency and colourlessness of the tissues, and the modifications of the foot, which still shows in _Atlanta_ the form common in Pectinibranchia (compare fig. 27 and fig. 24). The cylindrical body of _Pterotrachaea_ is paralleled by the slug-like forms of Euthyneura. J.W. Spengel has shown that the visceral loop of the Heteropoda is streptoneurous. Special to the Heteropoda is the high elaboration of the lingual ribbon, and, as an agreement with some of the opisthobranchiate Euthyneura, but as a difference from the Pectinibranchia, we find the otocysts closely attached to the cerebral ganglia. This is, however, less of a difference than it was at one time supposed to be, for it has been shown by H. Lacaze-Duthiers, and also by F. Leydig, that the otocysts of Pectinibranchia even when lying close upon the pedal ganglion (as in fig. 21) yet receive their special nerve (which can sometimes be readily isolated) from the cerebral ganglion (see fig. 11). Accordingly the difference is one of position of the otocyst and not of its nerve-supply. The Heteropoda are further remarkable for the high development of their cephalic eyes, and for the typical character of their osphradium (Spengel's olfactory organ). This is a groove, the edges of which are raised and ciliated, lying near the branchial plume in the genera which possess that organ, whilst in _Firoloida_, which has no branchial plume, the osphradium occupies a corresponding position. Beneath the ciliated groove is placed an elongated ganglion (olfactory ganglion) connected by a nerve to the supra-intestinal (therefore the primitively dextral) ganglion of the long visceral nerve-loop, the strands of which cross one another--this being characteristic of Streptoneura (Spengel).

The Heteropoda belong to the "pelagic fauna" occurring near the surface in the Mediterranean and great oceans in company with the Pteropoda, the Siphonophorous Hydrozoa, Salpae, Leptocephali, and other specially-modified transparent swimming representatives of various groups of the animal kingdom. In development they pass through the typical trochosphere and veliger stages provided with boat-like shell.

Sub-order 1.--TAENIOGLOSSA. Radula with a median tooth and three teeth on each side of it. Formula 3 : 1 : 3.

Tribe 1.--PLATYPODA. Normal Taenioglossa of creeping habit. The foot is flattened ventrally, at all events in its anterior part (_Strombidae_). Otocysts situated close to the pedal nerve-centres. Accessory organs are rarely found on the genital ducts, but occur in _Paludina, Cyclostoma, Naticidae, Calyptraeidae_, &c. Mandibles usually present. This is the largest group of Mollusca, including nearly sixty families, some of which are insufficiently known from the anatomical point of view.

Fam. 1.--_Paludinidae_. Pedal centres in the form of ganglionated cords; kidney provided with a ureter; viviparous; fluviatile. _Paludina_. _Neothauma_, from Lake Tanganyika. _Tylopoma_, extinct, Tertiary.

Fam. 2.--_Cyclophoridae_. No ctenidium, pallial cavity transformed into a lung; aperture of shell circular; terrestrial. _Pomatias_, shell turriculated. _Diplommatina. Hybocystis. Cyclophorus_, shell umbilicated, with a short spire and horny operculum. Cyclosurus, shell uncoiled. _Dermatocera_, foot with a horn-shaped protuberance at its posterior end. Spiraculum.

Fam. 3.--_Ampullariidae_. To the left of the ctenidium a pulmonary sac, separated from it by an incomplete septum, amphibious. _Ampullaria_, shell dextral, coiled. _Lanistes_, shell sinistral, spire short or obsolete. _Meladomus._

Fam. 4.--_Littorinidae._ Oesophageal pouches present; pedal nerve-centres concentrated; a pedal penis near the right tentacle. _Littorina_, shell not umbilicated, littoral habit. _Lacuna_, foot with two posterior appendages, marine, entirely aquatic. _Cremnoconchus_, entirely aerial, Indian. _Risella. Tectarius._

Fam. 5.--_Fossaridae._ Head with two lobes in some Rhipidoglossa. _Fossaria._

Fam. 6.--_Purpurinidae_, extinct.

Fam. 7.--_Planaxidae._ Shell with pointed spire; a short pallial siphon. Planaxis.

Fam. 8.--_Cyclostomatidae._ Pallial cavity transformed into a lung; pedal centres concentrated; a deep pedal groove. _Cyclostoma_, shell turbinated, operculum calcareous, British. _Omphalotropis._

Fam. 9.--_Aciculidae._ Pallial cavity transformed into a lung; operculum horny; shell narrow and elongated. _Acicula._

Fam. 10.--_Valvatidae._ Ctenidium bipectinate, free; hermaphrodite; fluviatile. _Valvata_, British.

Fam. 11.--_Rissoidae._ Epipodial filaments present; one or two pallial tentacles. _Rissoa. Rissoina. Stiva._

Fam. 12.--_Litiopidae._ An epipodium bearing three pairs of tentacles and an operculigerous lobe with two appendages; inhabitants of the Sargasso weed. _Litiopa._

Fam. 13.--_Adeorbiidae._ Mantle with two posterior appendages; ctenidium large and capable of protrusion from pallial cavity. _Adeorbis_, British.

Fam. 14.--_Jeffreysiidae._ Head with two long labial palps; shell ovoid; operculum horny, semicircular, carinated. _Jeffreysia._

Fam. 15.--_Homalogyridae._ Shell flattened; no cephalic tentacles. _Homalogyra_, British. _Ammoniceras._

Fam. 16.--_Skeneidae._ Shell depressed, with rounded aperture; cephalic tentacles long. _Skenea_, British.

Fam. 17.--_Choristidae._ Shell spiral; four cephalic tentacles; eyes absent; two pedal appendages. _Choristes._

Fam. 18.--_Assimineidae._ Eyes at free extremities of tentacles. Assiminea, estuarine, British.

Fam. 19.--_Truncatellidae._ Snout very long, bilobed; foot short. _Truncatella._

Fam. 20.--_Hydrobiidae._ Shell with prominent spire; penis distant from right tentacle, generally appendiculated; brackish water or fluviatile. _Hydrobia_, British. _Baikalia_, from Lake Baikal. _Pomatiopsis. Bithynella. Lithoglyphus. Spekia_, viviparous, from Lake Tanganyika. _Tanganyicia. Limnotrochus_, from Lake Tanganyika. _Chytra. Littorinida. Bithynia_, British, fluviatile. _Stenothyra._

Fam. 21.--_Melaniidae._ Spire of shell somewhat elongated; mantle-border fringed; viviparous; fluviatile. _Melania. Faunus. Paludomus. Melanopsis. Nassopsis. Bythoceras_, from Lake Tanganyika.

Fam. 22.--_Typhobiidae._ Foot wide; shell turriculated, with carinated whorls, the carinae tuberculated or spiny. _Typhobia. Bathanalia_, from Lake Tanganyika.

Fam. 23.--_Pleuroceridae._ Like _Melaniidae_, but mantle-border not fringed and reproduction oviparous. _Pleurocera. Anculotus._

Fam. 24.--_Pseudomelaniidae._ All extinct.

Fam. 25.--_Subulitidae._ All extinct.

Fam. 26.--_Nerineidae._ All extinct.

Fam. 27.--_Cerithiidae._ Shell with numerous tuberculated whorls; aperture canaliculated anteriorly; short pallial siphon. _Cerithium. Bittium. Potamides. Triforis. Laeocochlis. Cerithiopsis._

Fam. 28.--_Modulidae._ Shell with short spire; no siphon. _Modulus._

Fam. 29.--_Vermetidae._ Animal fixed by the shell, the last whorls of which are not in contact with each other; foot small; two anterior pedal tentacles. _Vermetus. Siliquaria._

Fam. 30.--_Caecidae._ Shell almost completely uncoiled, in one plane, with internal septa. _Caecum_, British.

Fam. 31.--_Turritellidae._ Shell very long; head large; foot broad. _Turritella_, British. _Mesalia. Mathilda._

Fam. 32.--_Struthiolariidae._ Shell conical; aperture slightly canaliculated; siphon slightly developed. _Struthiolaria._

Fam. 33.--_Chenopodidae._ Shell elongated; aperture expanded; siphon very short. _Chenopus_, British. _Alaria, Spinigera, Diartema_, extinct.

Fam. 34.--_Strombidae._ Foot narrow, compressed, without sole. _Strombus. Pteroceras. Rostellaria. Terebellum._

Fam. 35.--_Xenophoridae._ Foot transversely divided into two parts. _Xenophorus. Eotrochus_, Silurian.

Fam. 36.--_Capulidae._ Shell conical, not coiled, but slightly incurved posteriorly; a tongue-shaped projection between snout and foot. _Capulus. Thyca_, parasitic on asterids. _Platyceras_, extinct.

Fam. 37.--_Hipponycidae._ Shell conical; foot secreting a ventral calcareous plate; animal fixed. _Hipponyx. Mitrularia._

Fam. 38.--_Calyptraeidae._ Shell with short spire; lateral cervical lobes present; accessory genital glands. _Calyptraea_, British. _Crepidula. Crucibulum._

Fam. 39.--_Naricidae._ Foot divided into two, posterior half bearing the operculum; a wide epipodial velum; shell turbinated. Narica.

Fam. 40.--_Naticidae._ Foot large, with aquiferous system; propodium reflected over head; eyes degenerate; burrowing habit. _Natica_, British. _Amaura. Sigaretus._

Fam. 41.--_Lamellariidae._ Shell thin, more or less covered by the mantle; no operculum. _Lamellaria. Velutina. Marsenina_, _Oncidiopsis_, hermaphrodite.

Fam. 42.--_Trichotropidae._ Shell with short spire, carinate and pointed. _Trichotropis._

Fam. 43.--_Seguenziidae._ Shell trochiform, with canaliculated aperture and twisted columella. _Seguenzia_, abyssal.

Fam. 44.--_Janthinidae._ Shell thin; operculum absent; tentacles bifid; foot secretes a float; pelagic. _Janthina. Recluzia._

Fam. 45.--_Cypraeidae._ Shell inrolled, solid, polished, aperture very narrow in adult; short siphon; anus posterior; osphradium with three lobes; mantle reflected over shell. _Cypraea. Pustularia. Ovula. Pedicularia_, attached to corals. _Erato_.

Fam. 46.--_Tritonidae._ Shell turriculated and siphonated, thick, each whorl with varices; foot broad and truncated anteriorly; pallial siphon well developed; proboscis present. _Triton. Persona._ _Ranella._

Fam. 47.--_Columbellinidae._ All extinct.

Fam. 48.--_Cassididae._ Shell ventricose, with elongated aperture, and short spire; proboscis and siphon long; operculum with marginal nucleus. _Cassis. Cassidaria. Oniscia._

Fam. 49--_Oocorythidae._ Shell globular and ventricose; aperture oval and canaliculated; operculum spiral. _Oocorys_, abyssal.

Fam. 50.--_Doliidae._ Shell ventricose, with short spire, and wide aperture; no varices and no operculum; foot very broad, with projecting anterior angles; siphon long. _Dolium. Pyrula._

Fam. 51.--_Solariidae. Solarium. Torinia. Fluxina._

Fam. 52.--_Scalariidae._ Shell turriculated, with elongated spire; proboscis short; siphon rudimentary. _Scalaria. Eglisia._ Crossea. Aclis.

The three following families have neither radula nor jaws, and are therefore called _Aglossa_. They have a well-developed proboscis which is used as a suctorial organ; some are abyssal, but the majority are either commensals or parasites of Echinoderms.

Fam. 53.--_Pyramidellidae._ Summit of spire heterostrophic; a projection, the mentum, between head and foot; operculum present. _Pyramidella. Turbonilla. Odostomia_, British. _Myxa._

Fam. 54.--_Eulimidae._ Visceral mass still coiled spirally; shell thin and shining. _Eulima_, foot well developed, with an operculum, animal usually free, but some live in the digestive cavity of Holothurians. _Mucronalia_, foot reduced, but still operculate, eyes present, animal fixed by its very long proboscis which is deeply buried in the tissues of an Echinoderm, no pseudopallium. _Stylifer_, the operculum is lost, animal fixed by a large proboscis which forms a pseudopallium covering the whole shell except the extremity of the spire, parasitic on all groups of Echinoderms. _Entosiphon_, visceral mass still coiled; shell much reduced, proboscis very long forming a pseudopallium which covers the whole body and projects beyond in the form of a siphon, foot and nervous system present, eyes, branchia and anus absent, parasite in the Holothurian _Deima blakei_ in the Indian Ocean.

Fam. 55.--_Entoconchidae._ No shell; visceral mass not coiled; no sensory organs, nervous system, branchia or anus; body reduced to a more or less tubular sac; hermaphrodite and viviparous; parasitic in Holothurians; larvae are veligers, with shell and operculum. _Entocolax_, mouth at free extremity, animal fixed by aboral orifice of pseudopallium, Pacific. _Entoconcha_, body elongated and tubular, animal fixed by the oral extremity, protandric hermaphrodite, parasitic in testes of Holothurians causing their abortion. _Enteroxenos_, no pseudopallium and no intestine, hermaphrodite, larvae with operculum.

Tribe 2.--HETEROPODA. Pelagic Taenioglossa with foot large and laterally compressed to form a fin.

Fam. 1. _Atlantidae._ Visceral sac and shell coiled in one plane; foot divided transversely into two parts, posterior part bearing an operculum, anterior part forming a fin provided with a sucker. _Atlanta. Oxygyrus._

Fam. 2.--_Carinariidae._ Visceral sac and shell small in proportion to the rest of the body, which cannot be withdrawn into the shell; foot elongated, fin-shaped, with sucker, but without operculum. _Carinaria. Cardiopoda._

Fam. 3.--_Pterotrachaeidae._ Visceral sac very much reduced; without shell or mantle; anus posterior; foot provided with sucker in male only. _Pterotrachaea. Firoloida. Pterosoma._

Sub-order 2.--STENOGLOSSA. Radula narrow with one lateral tooth on each side, and one median tooth or none.

Tribe 1.--RACHIGLOSSA. Radula with a median tooth and a single tooth on each side of it. Formula 1 : 1 : 1. Rudimentary jaws present.

Fam. 1.--_Turbinellidae._ Shell solid, piriform, with thick folded columella; lateral teeth of radula bicuspidate. _Turbinella. Cynodonta. Fulgur. Hemifusus. Tudicla. Strepsidura._

Fam. 2.--_Fasciolariidae._ Shell elongated, with long siphon; lateral teeth of radula multicuspidate. _Fasciolaria. Fusus. Clavella. Latirus._

Fam. 3.--_Mitridae._ Shell fusiform and solid, aperture elongated, columella folded; no operculum; eyes on sides of tentacles. _Mitra. Turricula. Cylindromitra. Imbricaria._

Fam. 4.--_Buccinidae._ Foot large and broad; eyes at base of tentacles; operculum horny. _Buccinum. Chrysodomus. Liomesus. Cominella. Tritonidea. Pisania. Euthria. Phos. Dipsacus._

Fam. 5.--_Nassidae._ Foot broad, with two slender posterior appendages; operculum unguiculate. _Nassa_, marine, British. _Canidia_, fluviatile. _Bullia._

Fam. 6.--_Muricidae._ Shell with moderately long spire and canal, ornamented with ribs, often spiny; foot truncated anteriorly. _Murex_, British. _Trophon_, British. _Typhis. Urosalpinx. Lachesis._

Fam. 7.--_Purpuridae._ Shell thick, with short spire, last whorl large and canal short; aperture wide; operculum horny. _Purpura_, British. _Rapana. Monoceros. Sistrum. Concholepas._

Fam. 8.--_Haliidae._ Shell ventricose, thin and smooth, with wide aperture; foot large and thick, without operculum. _Halia._

Fam. 9.--_Cancellariidae._ Shell ovoid, with short spire and folded columella; foot small, no operculum; siphon short. _Cancellaria._

Fam. 10.--_Columbellidae._ Spire of shell prominent, aperture narrow, canal very short, columella crenelated; foot large. _Columbella._

Fam. 11.--_Coralliophilidae._ Shell irregular; radula absent; foot and siphon short; sedentary animals, living in corals. _Coralliophila. Rhizochilus. Leptoconchus. Magilus. Rapa._

Fam. 12.--_Volutidae._ Head much flattened and wide, with eyes on sides; foot broad; siphon with internal appendages. _Valuta. Guivillea. Cymba._

Fam. 13.--_Olividae._ Foot with anterior transverse groove; a posterior pallial tentacle; generally burrowing. _Olivia. Olivella. Ancillaria. Agaronia._

Fam. 14.--_Marginellidae._ Foot very large; mantle reflected over shell. _Marginella. Pseudomarginella._

Fam. 15.--_Harpidae._ Foot very large; without operculum; shell with short spire and longitudinal ribs; siphon long. _Harpa._

Tribe 2.--TOXIGLOSSA. No jaws. No median tooth in radula. Formula: 1 : 0 : 1. Poison-gland present whose duct traverses the nerve-collar.

Fam. 1.--_Pleurotomatidae._ Shell fusiform, with elongated spire; margin of shell and mantle notched. _Pleurotoma. Clavatula. Mangilia. Bela. Pusionella. Pontiothauma._

Fam. 2.--_Terebridae._ Shell turriculated, with numerous whorls; aperture and operculum oval; eyes at summits of tentacles; siphon long. _Terebra._

Fam. 3.--_Conidae._ Shell conical, with very short spire, and narrow aperture with parallel borders; operculum unguiform _Conus._

Sub-Class II.--EUTHYNEURA

The most important general character of the Euthyneura is the absence of torsion in the visceral commissure, and the more posterior position of the anus and pallial organs. Comparative anatomy and embryology prove that this condition is due, not as formerly supposed to a difference in the relations of the visceral commissure which prevented it from being included in the torsion of the visceral hump, but to an actual detorsion which has taken place in evolution and is repeated to a great extent in individual development. In several of the more primitive forms the same torsion occurs as in Streptoneura, viz. in _Actaeon_ and _Limacina_ among Opisthobranchia, and _Chilina_ among Pulmonata. _Actaeon_ is proso-branchiate, the visceral commissure is twisted in _Actaeon_ and _Chilina_, and even slightly still in _Bulla_ and _Scaphander_; in _Actaeon_ and _Limacina_ the osphradium is to the left, innervated by the supra-intestinal ganglion. But in the other members of the sub-class the detorsion of the visceral mass has carried back the anus and circumanal complex from the anterior dorsal region to the right side, as in _Bulla_ and _Aplysia_, or even to the posterior end of the body, as in _Philine, Oncidium, Doris_, &c. Different degrees of the same process of detorsion are, as we have seen, exhibited by the Heteropoda among the Streptoneura, and both in them and in the Euthyneura the detorsion is associated with degeneration of the shell. Where the modification is carried to its extreme degree, not only the shell but the pallial cavity, ctenidium and visceral hump disappear, and the body acquires a simple elongated form and a secondary external symmetry, as in _Pterotrachaea_ and in _Doris, Eolis_, and other Nudibranchia. These facts afford strong support to the hypothesis that the weight of the shell is the original cause of the torsion of the dorsal visceral mass in Gastropods. But this hypothesis leaves the elevation of the visceral mass and the exogastric coiling of the shell in the ancestral form unexplained. In those Euthyneura in which the shell is entirely absent in the adult, it is, except in the three genera _Cenia, Runcina_ and _Vaginula_, developed in the larva and then falls off. In other cases (Tectibranchs) the reduced shell is enclosed by upgrowths of the edge of the mantle and becomes internal, as in many Cephalopods. A few Euthyneura in which the shell is not much reduced retain an operculum in the adult state, e.g. _Actaeon, Limacina_, and the marine Pulmonate, _Amphibola_. The detorted visceral commissure shows a tendency to the concentration of all its elements round the oesophagus, so that except in the Bullomorpha and in _Aplysia_ the whole nervous system is aggregated in the cephalic region, either dorsally or ventrally. The radula has a number of uniform teeth on each side of the median tooth in each transverse row. The head in most cases bears two pairs of tentacles. All the Euthyneura are hermaphrodite.

In the most primitive condition the genital duct is single throughout its length and has a single external aperture; it is therefore said to be monaulic. The hermaphrodite aperture is on the right side near the opening of the pallial cavity, and a ciliated groove conducts the spermatozoa to the penis, which is situated more anteriorly. This is the condition in the Bullomorpha, the Aplysiomorpha, and in one Pulmonate, _Pythia_. In some cases while the original aperture remains undivided, the seminal groove is closed and so converted into a canal. This is the modification found in _Cavolinia longirostris_ among the Bullomorpha, and in all the _Auriculidae_ except _Pythia_. A further degree of modification occurs when the male duct takes its origin from the hermaphrodite duct above the external opening, so that there are two distinct apertures, one male and one female, the latter being the original opening. The genital duct is now said to be diaulic, as in _Valvata, Oncidiopsis, Actaeon_, and _Lobiger_ among the Bullomorpha, in the _Pleurobranchidae_, in the Nudibranchia, except the Doridomorpha and most of the Elysiomorpha, and in the Pulmonata. Originally in this condition the female aperture is at some distance from the male, as in the Basommatophora and in other cases; but in some forms the female aperture itself has shifted and come to be contiguous with the male opening and penis as in the Stylommatophora. In all these cases the female duct bears a bursa copulatrix or receptaculum seminis. In some forms this receptacle acquires a separate external opening remaining connected with the oviduct internally. There are thus two female openings, one for copulation, the other for oviposition, as well as a male opening. The genital duct is now trifurcated or triaulic, a condition which is confined to certain Nudibranchs, viz. the Doridomorpha and most of the Elysiomorpha.

The Pteropoda, formerly regarded as a distinct class of the Mollusca, were interpreted by E.R. Lankester as a branch of the Cephalopoda, chiefly on account of the protrusible sucker-bearing processes at the anterior end of _Pneumonoderma_. These he considered to be homologous with the arms of Cephalopods. He fully recognized, however, the similarity of Pteropods to Gastropods in their general asymmetry and in the torsion of the visceral mass in _Limacinidae_. It is now understood that they are Euthyneurous Gastropods adapted to natatory locomotion and pelagic life. The sucker-bearing processes of _Pneumonoderma_ are outgrowths of the proboscis. The fins of Pteropods are now interpreted as the expanded lateral margins of the foot, termed parapodia, not homologous with the siphon of Cephalopods which is formed from epipodia. The Thecosomatous Pteropoda are allied to _Bulla_, the Gymnosomatous forms to _Aplysia_. The Euthyneura comprises two orders, Opisthobranchia and Pulmonata.

Order 1.--OPISTHOBRANCHIA. Marine Euthyneura, the more archaic forms of which have a relatively large foot and a small visceral hump, from the base of which projects on the right side a short mantle-skirt. The anus is placed in such forms far back beyond the mantle-skirt. In front of the anus, and only partially covered by the mantle-skirt, is the ctenidium with its free end turned backwards. The heart lies in front of, instead of to the side of, the attachment of the ctenidium--hence Opisthobranchia as opposed to "Prosobranchia," which correspond to the Streptoneura. A shell is possessed in the adult state by but few Opisthobranchia, but all pass through a veliger larval stage with a nautiloid shell (fig. 36). Many Opisthobranchia have by a process of atrophy lost the typical ctenidium and the mantle-skirt, and have developed other organs in their place. As in some Pectinibranchia, the free margin of the mantle-skirt is frequently reflected over the shell when a shell exists; and, as in some Pectinibranchia, broad lateral outgrowths of the foot (parapodia) are often developed which may be thrown over the shell or naked dorsal surface of the body.

The variety of special developments of structure accompanying the atrophy of typical organs in the Opisthobranchia and general degeneration of organization is very great. The members of the order present the same wide range of superficial appearance as do the Pectinibranchiate Streptoneura, forms carrying well-developed spiral shells and large mantle-skirts being included in the group, together with flattened or cylindrical slug-like forms. But in respect of the substitution of other parts for the mantle-skirt and for the gill which the more degenerate Opisthobranchia exhibit, this order stands alone. Some Opisthobranchia are striking examples of degeneration (some Nudibranchia), having none of those regions or processes of the body developed which distinguish the archaic Mollusca from such flat-worms as the Dendrocoel Planarians. Indeed, were it not for their retention of the characteristic odontophore we should have little or no indication that such forms as _Phyllirhoë_ and _Limapontia_ really belong to the Mollusca at all. The interesting little _Rhodope veranyii_, which has no odontophore, has been associated by systematists both with these simplified Opisthobranchs and with Rhabdocoel Planarians.

In many respects the sea-hare (_Aplysia_), of which several species are known (some occurring on the English coast), serves as a convenient example of the fullest development of the organization characteristic of Opisthobranchia. The woodcut (fig. 38) gives a faithful representation of the great mobility of the various parts of the body. The head is well marked and joined to the body by a somewhat constricted neck. It carries two pairs of cephalic tentacles and a pair of sessile eyes. The visceral hump is low and not drawn out into a spire. The foot is long, carrying the oblong visceral mass upon it, and projecting (as metapodium) a little beyond it (f). Laterally the foot gives rise to a pair of mobile fleshy lobes, the parapodia (ep), which can be thrown up so as to cover in the dorsal surface of the animal. Such parapodia are common, though by no means universal, among Opisthobranchia. The torsion of the visceral hump is not carried out very fully, the consequence being that the anus has a posterior position a little to the right of the median line above the metapodium, whilst the branchial chamber formed by the overhanging mantle-skirt faces the right side of the body instead of lying well to the front as in Streptoneura and as in Pulmonate Euthyneura. The gill-plume, which in _Aplysia_ is the typical Molluscan ctenidium, is seen in fig. 39 projecting from the branchial sub-pallial space. The relation of the delicate shell to the mantle is peculiar, since it occupies an oval area upon the visceral hump, the extent of which is indicated in fig. 38, C, but may be better understood by a glance at the figures of the allied genus _Umbrella_ (fig. 40), in which the margin of the mantle-skirt coincides, just as it does in the limpet, with the margin of the shell. But in _Aplysia_ the mantle is reflected over the edge of the shell, and grows over its upper surface so as to completely enclose it, excepting at the small central area s where the naked shell is exposed. This enclosure of the shell is a permanent development of the arrangement seen in many Streptoneura (e.g. _Pyrula, Ovula_, see figs. 18 and 32), where the border of the mantle can be, and usually is, drawn over the shell, though it is withdrawn (as it cannot be in _Aplysia_) when they are irritated. From the fact that _Aplysia_ commences its life as a free-swimming veliger with a nautiloid shell not enclosed in any way by the border of the mantle, it is clear that the enclosure of the shell in the adult is a secondary process. Accordingly, the shell of _Aplysia_ must not be confounded with a primitive shell in its shell-sac, such as we find realized in the shells of _Chiton_ and in the plugs which form in the remarkable transitory "shell-sac" or "shell-gland" of Molluscan embryos (see figs. 26, 60). _Aplysia_, like other Mollusca, develops a primitive shell-sac in its trochosphere stage of development, which disappears and is succeeded by a nautiloid shell (fig. 36). This forms the nucleus of the adult shell, and, as the animal grows, becomes enclosed by a reflection of the mantle-skirt. When the shell of an _Aplysia_ enclosed in its mantle is pushed well to the left, the sub-pallial space is fully exposed as in fig. 39, and the various apertures of the body are seen. Posteriorly we have the anus, in front of this the lobate gill-plume, between the two (hence corresponding in position to that of the Pectinibranchia) we have the aperture of the renal organ. In front, near the anterior attachment of the gill-plume, is the osphradium (olfactory organ) discovered by J.W. Spengel, yellowish in colour, in the typical position, and overlying an olfactory ganglion with typical nerve-connexion (see fig. 43). To the right of Spengel's osphradium is the opening of a peculiar gland which has, when dissected out, the form of a bunch of grapes; its secretion is said to be poisonous. On the under side of the free edge of the mantle are situated the numerous small cutaneous glands which, in the large _Aplysia camelus_ (not in other species), form the purple secretion which was known to the ancients. In front of the osphradium is the single genital pore, the aperture of the common or hermaphrodite duct. From this point there passes forward to the right side of the head a groove--the spermatic groove--down which the spermatic fluid passes. In other Euthyneura this groove may close up and form a canal. At its termination by the side of the head is the muscular introverted penis. In the hinder part of the foot (not shown in any of the diagrams) is the opening of a large mucus-forming gland very often found in the Molluscan foot.

With regard to internal organization we may commence with the disposition of the renal organ (nephridium), the external opening of which has already been noted. The position of this opening and other features of the renal organ were determined by J.T. Cunningham.

There is considerable uncertainty with respect to the names of the species of _Aplysia_. There are two forms which are very common in the Gulf of Naples. One is quite black in colour, and measures when outstretched 8 or 9 in. in length. The other is light brown and somewhat smaller, its length usually not exceeding 7 in. The first is flaccid and sluggish in its movements, and has not much power of contraction; its epipodial lobes are enormously developed and extend far forward along the body; it gives out when handled an abundance of purple liquid, which is derived from cutaneous glands situated on the under side of the free edge of the mantle. According to F. Blochmann it is identical with _A. camelus_ of Cuvier. The other species is _A. depilans_; it is firm to the touch, and contracts forcibly when irritated; the secretion of the mantle-glands is not abundant, and is milky white in appearance. The kidney has similar relations in both species, and is identical with the organ spoken of by many authors as the triangular gland. Its superficial extent is seen when the folds covering the shell are cut away and the shell removed; the external surface forms a triangle with its base bordering the pericardium, and its apex directed posteriorly and reaching the the left-hand posterior corner of the shell-chamber. The dorsal surface of the kidney extends to the left beyond the shell-chamber beneath the skin in the space between the shell-chamber and the left parapodium.

When the animal is turned on its left-hand side and the mantle-chamber widely opened, the gill being turned over to the left, a part of the kidney is seen beneath the skin between the attachment of the gill and the right parapodium (fig. 39). On examination this is found to be the under surface of the posterior limb of the gland, the upper surface of which has just been described as lying beneath the shell. In the posterior third of this portion, close to that edge which is adjacent to the base of the gill, is the external opening (fig. 39, o).

When the pericardium is cut open from above in an animal otherwise entire, the anterior face of the kidney is seen forming the posterior wall of the pericardial chamber; on the deep edge of this face, a little to the left of the attachment of the auricle to the floor of the pericardium, is seen a depression; this depression contains the opening from the pericardium into the kidney.

To complete the account of the relations of the organ: the right anterior corner can be seen superficially in the wall of the mantle-chamber above the gill. Thus the base of the gill passes in a slanting direction across the right-hand side of the kidney, the posterior end being dorsal to the apex of the gland, and the anterior end ventral to the right-hand corner.

As so great a part of the whole surface of the kidney lies adjacent to external surfaces of the body, the remaining part which faces the internal organs is small; it consists of the left part of the under surface; it is level with the floor of the pericardium, and lies over the globular mass formed by the liver and convoluted intestine.

Thus the renal organ of _Aplysia_ is shown to conform to the Molluscan type. The heart lying within the adjacent pericardium has the usual form, a single auricle and ventricle. The vascular system is not extensive, the arteries soon ending in the well-marked spongy tissue which builds up the muscular foot, parapodia, and dorsal body-wall.

The alimentary canal commences with the usual buccal mass; the lips are cartilaginous, but not armed with horny jaws, though these are common in other Opisthobranchs; the lingual ribbon is multidenticulate, and a pair of salivary glands pour in their secretion. The oesophagus expands into a curious gizzard, which is armed internally with large horny processes, some broad and thick, others spinous, fitted to act as crushing instruments. From this we pass to a stomach and a coil of intestine embedded in the lobes of a voluminous liver; a caecum of large size is given off near the commencement of the intestine. The liver opens by two ducts into the digestive tract.

The generative organs lie close to the coil of intestine and liver, a little to the left side. When dissected out they appear as represented in fig. 41. The essential reproductive organ or gonad consists of both ovarian and testicular cells (see fig. 42). It is an ovo-testis. From it passes a common or hermaphrodite duct, which very soon becomes entwined in the spire of a gland--the albuminiparous gland. The latter opens into the common duct at the point k, and here also is a small diverticulum of the duct f. Passing on, we find not far from the genital pore a glandular spherical body (the spermatheca c) opening by means of a longish duct into the common duct, and then we reach the pore (fig. 39, k). Here the female apparatus terminates. But when the male secretion of the ovo-testis is active, the seminal fluid passes from the genital pore along the spermatic groove (fig. 39) to the penis, and is by the aid of that eversible muscular organ introduced into the genital pore of a second _Aplysia_, whence it passes into the spermatheca, there to await the activity of the female element of the ovo-testis of this second _Aplysia_. After an interval of some days--possibly weeks--the ova of the second _Aplysia_ commence to descend the hermaphrodite duct; they become enclosed in a viscid secretion at the point where the albuminiparous gland opens into the duct intertwined with it; and on reaching the point where the spermathecal duct debouches they are impregnated by the spermatozoa which escape now from the spermatheca and meet the ova.

The development of _Aplysia_ from the egg presents many points of interest from the point of view of comparative embryology, but in relation to the morphology of the Opisthobranchia it is sufficient to point to the occurrence of a trochosphere and a veliger stage (fig. 36), and of a shell-gland or primitive shell-sac (fig. 36, _shgr_), which is succeeded by a nautiloid shell.

In the nervous system of _Aplysia_ the great ganglion-pairs are well developed and distinct. The euthyneurous visceral loop is long, and presents only one ganglion (in _Aplysia camelus_, but two distinct ganglia joined to one another in _Aplysia hybrida_ of the English coast), placed at its extreme limit, representing both the right and left visceral ganglia and the third or abdominal ganglion, which are so often separately present. The diagram (fig. 43) shows the nerve connecting this abdomino-visceral ganglion with the olfactory ganglion of Spengel. It is also seen to be connected with a more remote ganglion--the genital. Such special irregularities in the development of ganglia upon the visceral loop, and on one or more of the main nerves connected with it, are very frequent. Our figure of the nervous system of _Aplysia_ does not give the small pair of buccal ganglia which are, as in all glossophorous Molluscs, present upon the nerves passing from the cerebral region to the odontophore.

For a comparison of various Opisthobranchs, _Aplysia_ will be found to present a convenient starting-point. It is one of the more typical Opisthobranchs, that is to say, it belongs to the section Tectibranchia, but other members of the suborder, namely, _Bulla_ and _Actaeon_ (figs. 44 and 45), are less abnormal than _Aplysia_ in regard to their shells and the form of the visceral hump. They have naked spirally twisted shells which may be concealed from view in the living animal by the expansion and reflection of the parapodia, but are not enclosed by the mantle, whilst _Actaeon_ is remarkable for possessing an operculum like that of so many Streptoneura.

The great development of the parapodia seen in _Aplysia_ is usual in Tectibranchiate Opisthobranchs. The whole surface of the body becomes greatly modified in those Nudibranchiate forms which have lost, not only the shell, but also the ctenidium. Many of these have peculiar processes developed on the dorsal surface (fig. 46, A, B), or retain purely negative characters (fig. 46, D). The chief modification of internal organization presented by these forms, as compared with _Aplysia_, is found in the condition of the alimentary canal. The liver is no longer a compact organ opening by a pair of ducts into the median digestive tract, but we find very numerous hepatic diverticula on a shortened axial tract (fig. 47). These diverticula extend usually one into each of the dorsal papillae or "cerata" when these are present. They are not merely digestive glands, but are sufficiently wide to act as receptacles of food, and in them the digestion of food proceeds just as in the axial portion of the canal. A precisely similar modification of the liver or great digestive gland is found in the scorpions, where the axial portion of the digestive canal is short and straight, and the lateral ducts sufficiently wide to admit food into the ramifications of the gland there to be digested; whilst in the spiders the gland is reduced to a series of simple caeca.

The typical character is retained by the heart, pericardium, and the communicating nephridium or renal organ in all Opisthobranchs. An interesting example of this is furnished by the fish-like transparent _Phyllirhoë_ (fig. 37), in which it is possible most satisfactorily to study in the living animal, by means of the microscope, the course of the blood-stream, and also the reno-pericardial communication. In many of the Nudibranchiate Opisthobranchs the nervous system presents a concentration of the ganglia (fig. 48), contrasting greatly with what we have seen in _Aplysia_. Not only are the pleural ganglia fused to the cerebral, but also the visceral to these (see in further illustration the condition attained by the Pulmonate _Limnaeus_, fig. 59), and the visceral loop is astonishingly short and insignificant (fig. 48, e'). That the parts are rightly thus identified is probable from J.W. Spengel's observation of the osphradium and its nerve-supply in these forms; the nerve to that organ, which is placed somewhat anteriorly--on the dorsal surface--being given off from the hinder part (visceral) of the right compound ganglion--the fellow to that marked A in fig. 48. The Eolid-like Nudibranchs, amongst other specialities of structure, possess (in some cases at any rate) apertures at the apices of the "cerata" or dorsal papillae, which lead from the exterior into the hepatic caeca. Some amongst them (_Tergipes, Eolis_) are also remarkable for possessing peculiarly modified cells placed in sacs (cnidosacs) at the apices of these same papillae, which resemble the "thread-cells" of the Coelentera. According to T.S. Wright and J.H. Grosvenor these nematocysts are derived from the hydroids on which the animals feed.

The development of many Opisthobranchia has been examined--e.g. _Aplysia, Pleurobranchidium, Elysia, Polycera, Doris, Tergipes_. All pass through trochosphere and veliger stages, and in all a nautiloid or boat-like shell is developed, preceded by a well-marked "shell-gland" (see fig. 36). The transition from the free-swimming veliger larva with its nautiloid shell (fig. 36) to the adult form has not been properly observed, and many interesting points as to the true nature of folds (whether parapodia or mantle or velum) have yet to be cleared up by a knowledge of such development in forms like _Tethys, Doris, Phyllidia_, &c. As in other Molluscan groups, we find even in closely-allied genera (for instance, in _Aplysia_ and _Pleurobranchidium_, and other genera), the greatest differences as to the _amount_ of food-material by which the egg-shell is encumbered. Some form their diblastula by emboly, others by epiboly; and in the later history of the further development of the enclosed cells (arch-enteron) very marked variations occur in closely-allied forms, due to the influence of a greater or less abundance of food-material mixed with the protoplasm of the egg.

Sub-order 1.--TECTIBRANCHIA. Opisthobranchs provided in the adult state with a shell and a mantle, except _Runcina, Pleurobranchaea, Cymbuliidae_, and some Aplysiomorpha. There is a ctenidium, except in some Thecosomata and Gymnosomata, and an osphradium.

Tribe 1.--BULLOMORPHA. The shell is usually well developed, except in _Runcina_ and _Cymbuliidae_, and may be external or internal. No operculum, except in _Actaeonidae_ and _Limacinidae_. The pallial cavity is always well developed, and contains the ctenidium, at least in part; ctenidium, except in _Lophocercidae_, of folded type. With the exception of the _Aplustridae, Lophocercidae_ and _Thecosomata_, the head is devoid of tentacles, and its dorsal surface forms a digging disk or shield. The edges of the foot form parapodia, often transformed into fins. Posteriorly the mantle forms a large pallial lobe under the pallial aperture. Stomach generally provided with chitinous or calcified masticatory plates. Visceral commissure fairly long, except in _Runcina, Lobiger_ and _Thecosomata_. Hermaphrodite genital aperture, connected with the penis by a ciliated groove, except in _Actaeon, Lobiger_ and _Cavolinia longirostris_, in which the spermiduct is a closed tube. Animals either swim or burrow.

Fam. 1.--_Actaeonidae._ Cephalic shield bifid posteriorly; margins of foot slightly developed; genital duct diaulic; visceral commissure streptoneurous; shell thick, with prominent spire and elongated aperture; a horny operculum. _Actaeon_, British. _Solidula. Tornatellaea_, extinct. _Adelactaeon. Bullina. Bullinula._

Fam. 2.--_Ringiculidae._ Cephalic disk enlarged anteriorly, forming an open tube posteriorly; shell external, thick, with prominent spire; no operculum. _Ringicula. Pugnus._

Fam. 3.--_Tornatinidae._ Margins of foot not prominent; no radula; shell external, with inconspicuous spire. _Tornatina_, British. _Retusa. Volvula._

Fam. 4.--_Scaphandridae._ Cephalic shield short, truncated posteriorly; eyes deeply embedded; three calcareous stomachal plates; shell external, with reduced spire. _Scaphander_, British. _Atys. Smaragdinella. Cylichna_, British. _Amphisphyra_, British.

Fam. 5.--_Bullidae._ Margins of foot well developed; eyes superficial; three chitinous stomachal plates; shell external, with reduced spire. Bulla, British. _Haminea_, British.

Fam. 6.--_Aceratidae._ Cephalic shield continuous with neck; twelve to fourteen stomachal plates; a posterior pallial filament passing through a notch in shell. _Acera_, British. _Cylindrobulla. Volutella._

Fam. 7.--_Aplustridae._ Foot very broad; cephalic shield with four tentacles; shell external, thin, without prominent spire. _Aplustrum. Hydatina. Micromelo._

Fam. 8.--_Philinidae._ Cephalic shield broad, thick and simple; shell wholly internal, thin, spire much reduced, aperture very large. _Philine_, British. _Cryptophthalmus. Chelinodura. Phanerophthalmus. Colpodaspis_, British. _Colobocephalus._

Fam. 9.--_Doridiidae._ Cephalic shield ending posteriorly in a median point; shell internal, largely membranous; no radula or stomachal plates. _Doridium. Navarchus._

Fam. 10.--_Gastropteridae._ Cephalic shield pointed behind; shell internal, chiefly membranous, with calcified nucleus, nautiloid; parapodia forming fins. _Gastropteron._

Fam. 11.--_Runcinidae._ Cephalic shield continuous with dorsal integument; no shell; ctenidium projecting from mantle cavity. _Runcina._

Fam. 12.--_Lophocercidae._ Shell external, globular or ovoid; foot elongated, parapodia separate from ventral surface; genital duct diaulic. _Lobiger. Lophocercus._

The next three families form the group formerly known as Thecosomatous Pteropods. They are all pelagic, the foot being entirely transformed into a pair of anterior fins; eyes are absent, and the nerve centres are concentrated on the ventral side of the oesophagus.

Fam. 13.--_Limacinidae._ Dextral animals, with shell coiled pseudo-sinistrally; operculum with sinistral spiral; pallial cavity dorsal. _Limacina_, British. _Peraclis_, ctenidium present.

Fam. 14.--_Cymbuliidae._ Adult without shell; a sub-epithelial pseudoconch formed by connective tissue; pallial cavity ventral. _Cymbulia. Cymbuliopsis. Gleba. Desmopterus._

Fam. 15.--_Cavoliniidae._ Shell not coiled, symmetrical; pallial cavity ventral. _Cavolinia. Clio. Cuvierina._

Tribe 2.--APLYSIOMORPHA. Shell more or less internal, much reduced or absent. Head bears two pairs of tentacles. Parapodia separate from ventral surface, and generally transformed into swimming lobes. Visceral commissure much shortened, except in _Aplysia_. Genital duct monaulic; hermaphrodite duct connected with penis by a ciliated groove. Animals either swim or crawl.

Fam. 1.--_Aplysiidae_. Shell partly or wholly internal, or absent; foot long, with well-developed ventral surface. _Aplysia. Dolabella. Dolabrifer. Aplysiella. Phyllaplysia. Notarchus_.

The next six families include the animals formerly known as Gymnosomatous Pteropods, characterized by the absence of mantle and shell, the reduction of the ventral surface of the foot, and the parapodial fins at the anterior end of the body. They are all pelagic.

Fam. 2.--_Pneumonodermatidae_. Pharynx evaginable, with suckers. _Pneumonoderma. Dexiobranchaea. Spongiobranchaea. Schizobrachium_.

Fam. 3.--_Clionopsidae_. No buccal appendages or suckers; a very long evaginable proboscis; a quadriradiate terminal branchia. _Clionopsis_.

Fam. 4.--_Notobranchaeidae_. Posterior branchia triradiate. Notobranchaea.

Fam. 5.--_Thliptodontidae_. Head very large, not marked off from the body; neither branchia nor suckers; fins situated near the middle of the body. _Thliptodon_.

Fam. 6.--_Clionidae_. No branchia of any kind; a short evaginable pharynx, bearing paired conical buccal appendages or "cephalocones." _Clione. Paraclione. Fowlerina_.

Fam. 7.--_Halopsychidae_. No branchia; two long and branched buccal appendages. _Halopsyche_.

Tribe 3.--PLEUROBRANCHOMORPHA. Two pairs of tentacles. Foot without parapodia; no pallial cavity, but always a single ctenidium situated on the right side between mantle and foot. Genital duct diaulic, without open seminal groove; male and female apertures contiguous. Visceral commissure short, tendency to concentration of all ganglia in dorsal side of oesophagus.

Fam. 1.--_Tylodinidae_. Shell external and conical; anterior tentacles form a frontal veil; ctenidium extending only over right side; a distinct osphradium. _Tylodina_.

Fam. 2.--_Umbrellidae_. Shell external, conical, much flattened; anterior tentacles very small, and situated with the mouth in a notch of the foot below the head; ctenidium very large. _Umbrella_.

Fam. 3.--_Pleurobranchidae_. Shell covered by mantle, or absent; anterior tentacles form a frontal veil; mantle contains spicules. _Pleurobranchus. Berthella. Haliotinella. Oscanius_, British. _Oscaniella. Oscaniopsis. Pleurobranchaea._

Sub-order 2.--NUDIBRANCHIA. Shell absent in the adult; no ctenidium or osphradium. Body generally slug-like, and externally symmetrical. Visceral mass not marked off from the foot, except in _Hedylidae._ Dorsal respiratory appendages frequently present. Visceral commissure reduced; nervous system concentrated on dorsal side of oesophagus. Marine; generally carnivorous, and brightly coloured, affording many instances of protective resemblance.

Tribe 1.--TRITONIOMORPHA. Liver wholly or partially contained in the visceral mass. Anus lateral, on the right side. Usually two rows of ramified dorsal appendages. Genital duct diaulic; male and female apertures contiguous.

Fam. 1.--_Tritoniidae._ Anterior tentacles form a frontal veil; foot rather broad. _Tritonia_, British. _Marionia._

Fam. 2.--_Scyllaeidae._ No anterior tentacles; dorsal appendages broad and foliaceous; foot very narrow; stomach with horny plates. _Scyllaea_, pelagic.

Fam. 3.--_Phyllirhoidae._ No anterior tentacles, and no dorsal appendages; body laterally compressed, transparent; pelagic. _Phyllirhoë._

Fam. 4.--_Tethyidae._ Head broad, surrounded by a funnel-shaped velum or hood; no radula; dorsal appendages foliaceous. _Tethys. Melibe._

Fam. 5.--_Dendronotidae._ Anterior tentacles forming a scalloped frontal veil; dorsal appendages and tentacles similarly ramified. _Dendronotus. Campaspe._

Fam. 6.--_Bornellidae._ Dorsum furnished on either side with papillae, at the base of which are ramified appendages. _Bornella._

Fam. 7.--_Lomanotidae._ Body flattened, the two dorsal borders prominent and foliaceous. _Lomanotus_, British.

Tribe 2.--DORIDOMORPHA. Body externally symmetrical; anus median, posterior, and generally dorsal, surrounded by ramified pallial appendages, constituting a secondary branchia. Liver not ramified in the integuments. Genital duct triaulic. Spicules present in the mantle.

Fam. 1.--_Polyceratidae._ A more or less prominent frontal veil; branchiae non-retractile. _Euplocamus. Polycera_, British. _Thecacera_, British. _Aegirus_, British. _Plocamopherus. Palio. Crimora. Triopa_, British. _Triopella._

Fam. 2.--_Goniodorididae._ Mantle-border projecting; frontal veil reduced, and often covered by the anterior border of the mantle. _Goniodoris_, British. _Acanthodoris_, British. _Idalia_, British. _Ancula_, British. _Doridunculus_. _Lamellidoris. Ancylodoris_, the only fresh-water Nudibranch, from Lake Baikal.

Fam. 3.--_Heterodorididae_. No branchia. _Heterodoris_.

Fam. 4.--_Dorididae_. Mantle oval, covering the head and the greater part of the body; anterior tentacles, ill-developed; branchiae generally retractile. _Doris_, British. _Hexabranchus_. _Chromodoris_.

Fam. 5.--_Doridopsidae_. Pharynx suctorial; no radula; branchial rosette on the dorsal surface, above the mantle-border. _Doridopsis_.

Fam. 6.--_Corambidae_. Anus and branchia posterior, below the mantle-border. _Corambe_.

Fam. 7.-_-Phyllidiidae_. Pharynx suctorial; branchiae surrounding the body, between the mantle and foot. _Phyllidia. Fryeria_.

The last three families constitute the sub-tribe Porostomata, characterized by the reduction of the buccal mass, which is modified into a suctorial apparatus.

Tribe 3.--EOLIDOMORPHA (_Cladohepatica_). The whole of the liver contained in the integuments and tegumentary papillae. Genital duct diaulic; male and female apertures contiguous. The anus is antero-lateral, except in the _Proctonotidae_, in which it is median. Tegumentary papillae not ramified, and containing cnidosacs with nematocysts.

Fam. 1.--_Eolididae_. Dorsal papillae spindle-shaped or club-shaped. _Eolis_, British. _Facelina_, British. _Tergipes_, British. _Gonieolis. Cuthona. Embletonia. Galvina. Calma. Hero_.

Fam. 2.--_Glaucidae_. Body furnished with three pairs of lateral lobes, bearing the tegumentary papillae; foot very narrow; pelagic. _Glaucus_.

Fam. 3.--_Hedylidae_. Body elongated; visceral mass marked off from foot posteriorly; dorsal appendages absent, or reduced to a single pair; spicules in the integument. _Hedyle_.

Fam. 4.--_Pseudovermidae_. Head without tentacles; body elongated; anus on right side. _Pseudovermis_.

Fam. 5.--_Proctonotidae_. Anus posterior, median; anterior tentacles, atrophied; foot broad. _Janus_, British. _Proctonotus_, British.

Fam. 6.--_Dotonidae_. Bases of the rhinophores surrounded by a sheath; dorsal papillae tuberculated and club-shaped, in a single row on either side of the dorsum; no cnidosacs. _Doto_, British. _Gellina. Heromorpha_.

Fam. 7.--_Fionidae_. Dorsal papillae with a membranous expansion; male and female apertures at some distance from each other; pelagic. _Fiona_.

Fam. 8.--_Pleurophyllidae_. Anterior tentacles in the form of a digging shield; mantle without appendages, but respiratory papillae beneath the mantle-border. _Pleurophyllidia_.

Fam. 9.--_Dermatobranchidae_. Like the last, but wholly without branchiae. _Dermatobranchus_.

Tribe 4.--ELYSIOMORPHA. Liver ramifies in integuments and extends into dorsal papillae, but there are no cnidosacs. Genital duct always triaulic, and male and female apertures distant from each other. No mandibles, and radula uniserial. Never more than one pair of tentacles, and these are absent in _Alderia_ and some species of _Limapontia_.

Fam. 1.--_Hermaeidae_. Foot narrow; dorsal papillae linear or fusiform, in several series. _Hermaea_, British. _Stiliger_. _Alderia_, British.

Fam. 2.--_Phyllobranchidae_. Foot broad; dorsal papillae flattened and foliaceous. _Phyllobranchus. Cyerce_.

Fam. 3.--_Plakobranchidae_. Body depressed, without dorsal papillae, but with two very large lateral expansions, with dorsal plications. _Plakobranchus_.

Fam. 4.--_Elysiidae_. Body elongated, with lateral expansions; tentacles large; foot narrow. _Elysia_, British. _Tridachia_.

Fam. 5.--_Limapontiidae_. No lateral expansions, and no dorsal papillae; body planariform; anus dorsal, median and posterior. _Limapontia_, British. _Actaeonia_, British. _Cenia_.

Order 2 (of the Euthyneura).--PULMONATA. Euthyneurous Gastropoda, probably derived from ancestral forms similar to the Tectibranchiate Opisthobranchia by adaptation to a terrestrial life. The ctenidium is atrophied, and the edge of the mantle-skirt is fused to the dorsal integument by concrescence, except at one point which forms the aperture of the mantle-chamber, thus converted into a nearly closed sac. Air is admitted to this sac for respiratory and hydrostatic purposes, and it thus becomes a lung. An operculum is present only in _Amphibola_; a contrast being thus afforded with the operculate pulmonate Streptoneura (_Cyclostoma_, &c.), which differ in other essential features of structure from the Pulmonata. The Pulmonata are, like the other Euthyneura, hermaphrodite, with elaborately developed copulatory organs and accessory glands. Like other Euthyneura, they have very numerous small denticles on the lingual ribbon. In aquatic Pulmonata the osphradium is retained.

In some Pulmonata (snails) the foot is extended at right angles to the visceral hump, which rises from it in the form of a coil as in Streptoneura; in others the visceral hump is not elevated, but is extended with the foot, and the shell is small or absent (slugs).

Pulmonata are widely distinguished from a small number of Streptoneura at one time associated with them on account of their mantle-chamber being converted, as in Pulmonata, into a lung, and the ctenidium or branchial plume aborted. The terrestrial Streptoneura (represented in England by the common genus _Cyclostoma_) have a twisted visceral nerve-loop, an operculum on the foot, a complex rhipidoglossate or taenio-glossate radula, and are of distinct sexes. The Pulmonata have a straight visceral nerve-loop, usually no operculum even in the embryo, and a multidenticulate radula, the teeth being equi-formal; and they are hermaphrodite. Some Pulmonata (_Limnaea_, &c.) live in fresh waters although breathing air. The remarkable discovery has been made that in deep lakes such _Limnaei_ do not breathe air, but admit water to the lung-sac and live at the bottom. The lung-sac serves undoubtedly as a hydrostatic apparatus in the aquatic Pulmonata, as well as assisting respiration.

The same general range of body-form is shown in Pulmonata as in the Heteropoda and in the Opisthobranchia; at one extreme we have snails with coiled visceral hump, at the other cylindrical or flattened slugs (see fig. 56). Limpet-like forms are also found (fig. 57, _Ancylus_). The foot is always simple, with its flat crawling surface extending from end to end, but in the embryo _Limnaea_ it shows a bilobed character, which leads on to the condition characteristic of Pteropoda.

The adaptation of the Pulmonata to terrestrial life has entailed little modification of the internal organization. In one genus (_Planorbis_) the plasma of the blood is coloured red by haemoglobin, this being the only instance of the presence of this body in the blood of Glossophorous Mollusca, though it occurs in corpuscles in the blood of the bivalves _Arca_ and _Solen_ (Lankester).

The generative apparatus of the snail (_Helix_) may serve as an example of the hermaphrodite apparatus common to the Pulmonata and Opisthobranchia (fig. 58). From the ovo-testis, which lies near the apex of the visceral coil, a common hermaphrodite duct ve proceeds, which receives the duct of the compact white albuminiparous gland, Ed, and then becomes much enlarged, the additional width being due to the development of glandular folds, which are regarded as forming a uterus u. Where these folds cease the common duct splits into two portions, a male and a female. The male duct vd becomes fleshy and muscular near its termination at the genital pore, forming the penis p. Attached to it is a diverticulum fl, in which the spermatozoa which have descended from the ovo-testis are stored and modelled into sperm ropes or spermatophores. The female portion of the duct is more complex. Soon after quitting the uterus it is joined by a long duct leading from a glandular sac, the spermatheca (Rf). In this duct and sac the spermatophores received in copulation from another snail are lodged. In _Helix hortensis_ the spermatheca is simple. In other species of _Helix_ a second duct (as large in _Helix aspersa_ as the chief one) is given off from the spermathecal duct, and in the natural state is closely adherent to the wall of the uterus. This second duct has normally no spermathecal gland at its termination, which is simple and blunt. But in rare cases in _Helix aspersa_ a second spermatheca is found at the end of this second duct. Tracing the widening female duct onwards we now come to the openings of the digitate accessory glands d, d, which probably assist in the formation of the egg-capsule. Close to them is the remarkable dart-sac ps, a thick-walled sac, in the lumen of which a crystalline four-fluted rod or dart consisting of carbonate of lime is found. It is supposed to act in some way as a stimulant in copulation, but possibly has to do with the calcareous covering of the egg-capsule. Other Pulmonata exhibit variations of secondary importance in the details of this hermaphrodite apparatus.

The nervous system of _Helix_ is not favourable as an example on account of the fusion of the ganglia to form an almost uniform ring of nervous matter around the oesophagus. The pond-snail (_Limnaeus_) furnishes, on the other hand, a very beautiful case of distinct ganglia and connecting cords (fig. 59). The demonstration which it affords of the extreme shortening of the Euthyneurous visceral nerve-loop is most instructive and valuable for comparison with and explanation of the condition of the nervous centres in Cephalopoda, as also of some Opisthobranchia. The figure (fig. 59) is sufficiently described in the letterpress attached to it; the pair of buccal ganglia joined by the connectives to the cerebrals are, as in most of our figures, omitted. Here we need only further draw attention to the osphradium, discovered by Lacaze-Duthiers, and shown by Spengel to agree in its innervation with that organ in all other Gastropoda. On account of the shortness of the visceral loop and the proximity of the right visceral ganglion to the oesophageal nerve-ring, the nerve to the osphradium and olfactory ganglion is very long. The position of the osphradium corresponds more or less closely with that of the vanished right ctenidium, with which it is normally associated. In _Helix_ and _Limax_ the osphradium has not been described, and possibly its discovery might clear up the doubts which have been raised as to the nature of the mantle-chamber of those genera. In _Planorbis_, which is sinistral (as are a few other genera or exceptional varieties of various Anisopleurous Gastropods), instead of being dextral, the osphradium is on the left side, and receives its nerve from the left visceral ganglion, the whole series of unilateral organs being reversed. This is, as might be expected, what is found to be the case in all "reversed" Gastropods.

The shell of the Pulmonata, though always light and delicate, is in many cases a well-developed spiral "house" into which the creature can withdraw itself; and, although the foot possesses no operculum, yet in _Helix_ the aperture of the shell is closed in the winter by a complete lid, the "hybernaculum" more or less calcareous in nature, which is secreted by the foot. In _Clausilia_ a peculiar modification of this lid exists permanently in the adult, attached by an elastic stalk to the mouth of the shell, and known as the "clausilium." In _Limnaeus_ the permanent shell is preceded in the embryo by a well-marked shell-gland or primitive shell-sac (fig. 60), at one time supposed to be the developing anus, but shown by Lankester to be identical with the "shell-gland" discovered by him in other Mollusca (_Pisidium, Pleurobranchidium, Neritina_, &c.). As in other Gastropoda Anisopleura, this shell-sac may abnormally develop a plug of chitinous matter, but normally it flattens out and disappears, whilst the cap-like rudiment of the permanent shell is shed out from the dome-like surface of the visceral hump, in the centre of which the shell-sac existed for a brief period.

In _Clausilia_, according to the observations of C. Gegenbaur, the primitive shell-sac does not flatten out and disappear, but takes the form of a flattened closed sac. Within this closed sac a plate of calcareous matter is developed, and after a time the upper wall of the sac disappears, and the calcareous plate continues to grow as the nucleus of the permanent shell. In the slug _Testacella_ (fig. 56, C) the shell-plate never attains a large size, though naked. In other slugs, namely, _Limax_ and _Arion_, the shell-sac remains permanently closed over the shell-plate, which in the latter genus consists of a granular mass of carbonate of lime. The permanence of the primitive shell-sac in these slugs is a point of considerable interest. It is clear enough that the sac is of a different origin from that of _Aplysia_ (described in the section treating of Opisthobranchia), being primitive instead of secondary. It seems probable that it is identical with one of the open sacs in which each shell-plate of a _Chiton_ is formed, and the series of plate-like imbrications which are placed behind the single shell-sac on the dorsum of the curious slug, _Plectrophorus_, suggest the possibility of the formation of a series of shell-sacs on the back of that animal similar to those which we find in _Chiton_. Whether the closed primitive shell-sac of the slugs (and with it the transient embryonic shell-gland of all other Mollusca) is precisely the same thing as the closed sac in which the calcareous pen or shell of the Cephalopod _Sepia_ and its allies is formed, is a further question which we shall consider when dealing with the Cephalopoda. It is important here to note that _Clausilia_ furnishes us with an exceptional instance of the _continuity_ of the shell or secreted product of the primitive shell-sac with the adult shell. In most other Mollusca (Anisopleurous Gastropods, Pteropods and Conchifera) there is a want of such continuity; the primitive shell-sac contributes no factor to the permanent shell, or only a very minute knob-like particle (_Neritina_ and _Paludina_). It flattens out and disappears before the work of forming the permanent shell commences. And just as there is a break at this stage, so (as observed by A. Krohn in _Marsenia_ = _Echinospira_) there _may_ be a break at a later stage, the nautiloid shell formed on the larva being cast, and a new shell of a different form being formed afresh on the surface of the visceral hump. It is, then, in this sense that we may speak of primary, secondary and tertiary shells in Mollusca recognizing the fact that they _may_ be merely phases fused by continuity of growth so as to form but one shell, or that in other cases they _may_ be presented to us as separate individual things, in virtue of the non-development of the later phases, or in virtue of sudden changes in the activity of the mantle-surface causing the shedding or disappearance of one phase of shell-formation before a later one is entered upon.

The development of the aquatic Pulmonata from the egg offers considerable facilities for study, and that of _Limnaeus_ has been elucidated by E.R. Lankester, whilst H. Rabl has with remarkable skill applied the method of sections to the study of the minute embryos of _Planorbis_. The chief features in the development of _Limnaeus_ are exhibited in fig. 60. There is not a very large amount of food-material present in the egg of this snail, and accordingly the cells resulting from division are not so unequal as in many other cases. The four cells first formed are of equal size, and then four smaller cells are formed by division of these four so as to lie at one end of the first four (the pole corresponding to that at which the "directive corpuscles" are extruded and remain). The smaller cells now divide and spread over the four larger cells; at the same time a space--the cleavage cavity or blastocoel--forms in the centre of the mulberry-like mass. Then the large cells recommence the process of division and sink into the hollow of the sphere, leaving an elongated groove, the blastopore, on the surface. The invaginated cells (derived from the division of the four big cells) form the endoderm or arch-enteron; the outer cells are the ectoderm. The blastopore now closes along the middle part of its course, which coincides in position with the future "foot." One end of the blastopore becomes nearly closed, and an ingrowth of ectoderm takes place around it to form the stomodaeum or fore-gut and mouth. The other extreme end closes, but the invaginated endoderm cells remain in continuity with this extremity of the blastopore, and form the "rectal peduncle" or "pedicle of invagination" of Lankester, although the endoderm cells retain no contact with the middle region of the now closed-up blastopore. The anal opening forms at a late period by a very short ingrowth or proctodaeum coinciding with the blind termination of the rectal peduncle (fig. 60, pi).

The body-cavity and the muscular, fibrous and vascular tissues are traced partly to two symmetrically disposed "mesoblasts," which bud off from the invaginated arch-enteron, partly to cells derived from the ectoderm, which at a very early stage is connected by long processes with the invaginated endoderm. The external form of the embryo goes through the same changes as in other Gastropods, and is not, as was held previously to Lankester's observations, exceptional. When the middle and hinder regions of the blastopore are closing in, an equatorial ridge of ciliated cells is formed, converting the embryo into a typical trochosphere.

The foot now protrudes below the mouth, and the post-oral hemisphere of the trochosphere grows more rapidly then the anterior or velar area. The young foot shows a bilobed form. Within the velar area the eyes and the cephalic tentacles commence to rise up, and on the surface of the post-oral region is formed a cap-like shell and an encircling ridge, which gradually increases in prominence and becomes the freely depending mantle-skirt. The outline of the velar area becomes strongly emarginated and can be traced through the more mature embryos to the cephalic lobes or labial processes of the adult _Limnaeus_ (fig. 61).

The increase of the visceral dome, its spiral twisting, and the gradual closure of the space overhung by the mantle-skirt so as to convert it into a lung-sac with a small contractile aperture, belong to stages in the development later than any represented in our figures.

We may now revert briefly to the internal organization at a period when the trochosphere is beginning to show a prominent foot growing out from the area where the mid-region of the elongated blastopore was situated, and having therefore at one end of it the mouth and at the other the anus. Fig. 60 represents such an embryo under slight compression as seen by transmitted light. The ciliated band of the left side of the velar area is indicated by a line extending from v to v; the foot f is seen between the pharynx ph and the pedicle of invagination pi. The mass of the arch-enteron or invaginated endodermal sac has taken on a bilobed form, and its cells are swollen (gs and tge). This bilobed sac becomes _entirely_ the liver in the adult; the intestine and stomach are formed from the pedicle of invagination, whilst the pharynx, oesophagus and crop form from the stomodaeal invagination ph. To the right (in the figure) of the rectal peduncle is seen the deeply invaginated shell-gland ss, with a secretion sh protruding from it. The shell-gland is destined in _Limnaeus_ to become very rapidly stretched out, and to disappear. Farther up, within the velar area, the rudiments of the cerebral nerve-ganglion ng are seen separating from the ectoderm. A remarkable cord of cells having a position just below the integument occurs on each side of the head. In the figure the cord of the left side is seen, marked re. This paired organ consists of a string of cells which are perforated by a duct opening to the exterior and ending internally in a flame-cell. Such cannulated cells are characteristic of the nephridia of many worms, and the organs thus formed in the embryo _Limnaeus_ are embryonic nephridia. The most important fact about them is that they disappear, and are in no way connected with the typical nephridium of the adult. In reference to their first observer they were formerly called "Stiebel's canals." Other Pulmonata possess, when embryos, Stiebel's canals in a more fully developed state, for instance, the common slug _Limax_. Here too they disappear during embryonic life. Similar larval nephridia occur in other Gastropoda. In the marine Streptoneura they are ectodermic projections which ultimately fall off; in the Opisthobranchs they are closed pouches; in _Paludina_ and _Bithynia_ they are canals as in Pulmonata.

_Marine Pulmonata._--Whilst the Pulmonata are essentially a terrestrial and fresh-water group, there is one genus of slug-like Pulmonates which frequent the sea-coast (_Oncidium_, fig. 62). Karl Semper has shown that these slugs have, in addition to the usual pair of cephalic eyes, a number of eyes developed upon the dorsal integument. These dorsal eyes are very perfect in elaboration, possessing lens, retinal nerve-end cells, retinal pigment and optic nerve. Curiously enough, however, they differ from the cephalic Molluscan eye in the fact that, as in the vertebrate eye, the filaments of the optic nerve penetrate the retina, and are connected with the surfaces of the nerve-end cells nearer the lens instead of with the opposite end. The significance of this arrangement is not known, but it is important to note, as shown by V. Henson, S.J. Hickson and others, that in the bivalves _Pecten_ and _Spondylus_, which also have eyes upon the mantle quite distinct from typical cephalic eyes, there is the same relationship as in Oncidiidae of the optic nerve to the retinal cells. In both Oncidiidae and _Pecten_ the pallial eyes have probably been developed by the modification of tentacles, such as coexist in an unmodified form with the eyes. The Oncidiidae are, according to K. Semper, pursued as food by the leaping fish _Periophthalmus_, and the dorsal eyes are of especial value to them in aiding them to escape from this enemy.

Sub-order 1.--BASOMMATOPHORA. Pulmonata with an external shell. The head bears a single pair of contractile but not invaginable tentacles, at the base of which are the eyes. Penis at some distance from the female aperture, except in _Amphibola_ and _Siphonaria_. All have an osphradium, except the _Auriculidae_, which are terrestrial, and it is situated outside the pallial cavity in those forms in which water is not admitted into the lung. There is a veliger stage in development, but the velum is reduced.

Fam. 1.--_Auriculidae_. Terrestrial and usually littoral; genital duct monaulic, the penis being connected with the aperture by an open or closed groove; shell with a prominent spire, the internal partitions often absorbed and the aperture denticulated. _Auricula. Cassidula. Alexia. Melampus. Carychium_, terrestrial, British. _Scarabus. Leuconia_, British. _Blauneria. Pedipes_.

Fam. 2.--_Otinidae_. Shell with short spire, and wide oval aperture; tentacles short. _Otina_, British. _Camptonyx_, terrestrial.

Fam. 3.--_Amphibolidae_. Shell spirally coiled; head broad, without prominent tentacles; foot short, operculated; marine. _Amphibola_.

Fam. 4.--_Siphonariidae_. Visceral mass and shell conical; tentacles atrophied; head expanded; genital apertures contiguous; marine animals, with an aquatic pallial cavity containing secondary branchial laminae. _Siphonaria_.

Fam. 5.--_Gadiniidae_. Visceral mass and shell conical; head flattened; pallial cavity aquatic, but without a branchia; genital apertures separated. _Gadinia_.

Fam. 6.--_Chilinidae_. Shell ovoid, with short spire, wide aperture and folded columella; inferior pallial lobe thick; visceral commissure still twisted. _Chilina_.

Fam. 7.--_Limnaeidae_. Shell thin, dextral, with prominent spire and oval aperture; no inferior pallial lobe. _Limnaea_, British. _Amphipeplea_, British.

Fam. 8.--_Pompholygidae_. Shell dextral, hyperstrophic, animal sinistral. _Pompholyx. Choanomphalus_.

Fam. 9.--_Planorbidae_. Visceral mass and shell sinistral; inferior pallial lobe very prominent, and transformed into a branchia. _Planorbis_, British. _Bulinus. Miratesta_.

Fam. 10.--_Ancylidae_. Shell conical, not spiral; inferior pallial lobe transformed into a branchia. _Ancylus_, British. _Latia. Grundlachia_.

Fam. 11.--_Physidae_. Visceral mass and shell sinistrally coiled; shell thin, with narrow aperture; no inferior pallial lobe. _Physa_, British. _Aplexa_, British.

Sub-order 2.--STYLOMMATOPHORA. Pulmonata with two pairs of tentacles, except _Janellidae_ and _Vertigo_; these tentacles are invaginable, and the eyes are borne on the summits of the posterior pair. Male and female genital apertures open into a common vestibule, except in _Vaginulidae_ and _Oncidiidae_. Except in _Oncidium_, there is no longer a veliger stage in development.

Tribe 1.--HOLOGNATHA. Jaw simple, without a superior appendage.

Fam. 1.--_Selenitidae_. Radula with elongated and pointed teeth, like those of the Agnatha; a jaw present. _Plutonia. Trigonochlamys_.

Fam. 2.--_Zonitidae_. Shell external, smooth, heliciform or flattened; radula with pointed marginal teeth. _Zonites_, British. _Ariophanta. Orpiella. Vitrina. Helicarion_.

Fam. 3.--_Limacidae_. Shell internal. _Limax_, British. _Parmacella. Urocyclus. Parmarion. Amalia. Agriolimax. Mesolimax. Monochroma. Paralimax. Metalimax_.

Fam. 4.--_Philomycidae_. No shell; mantle covers the whole surface of the body; radula with squarish teeth. _Philomycus_.

Fam. 5.--_Ostracolethidae_. Shell largely chitinous, not spiral, its calcareous apex projecting through a small hole in the mantle. _Ostracolethe_.

Fam. 6.--_Arionidae_. Shell internal, or absent; mantle restricted to the anterior and middle part of the body; radula with squarish teeth. _Arion_, British. _Geomalacus. Ariolimax. Anadenus_.

Fam. 7.--_Helicidae_. Shell with medium spire, external or partly covered by the mantle; genital aperture below the right posterior tentacle; genital apparatus generally provided with a dart-sac and multifid vesicles. _Helix_, British. _Bulimus. Hemphillia. Berendtia. Cochlostyla. Rhodea_.

Fam. 8.--_Endodontidae_. Shell external, spiral, generally ornamented with ribs; borders of aperture thin and not reflected; radula with square teeth; genital ducts without accessory organs. _Endodonta. Punctum. Sphyradium. Laoma. Pyramidula._

Fam. 9.--_Orthalicidae._ Shell external, ovoid, the last whorl swollen, aperture oval with a simple border; radular teeth in oblique rows. _Orthalicus._

Fam. 10.--_Bulimulidae._ Jaw formed of folds imbricated externally and meeting at an acute angle near the base. _Bulimulus. Peltella. Amphibulimus._

Fam. 11.--_Cylindrellidae._ Shell turriculated, with numerous whorls, the last more or less detached. _Cylindrella._

Fam. 12.--_Pupidae._ Shell external, with elongated spire and numerous whorls, aperture generally narrow; male genital duct without multifid vesicles. _Pupa_, British. _Eucalodium. Vertigo_, British. _Buliminus_, British. _Clausilia_, British. _Balea. Zospeum. Megaspira. Strophia. Anostoma._

Fam. 13.--_Stenogyridae._ Shell elongated, with a more or less obtuse summit; aperture with a simple border. _Achatina. Stenogyra. Ferussacia_, British. _Cionella. Caecilianella. Azeca. Opeas._

Fam. 14.--_Helicteridae._ Shell bulimoid, dextral or sinistral; radular teeth, expanded at their extremities and multicuspidate. _Helicter. Tornatellina._

Tribe 2.--AGNATHA. No jaws; teeth narrow and pointed; carnivorous.

Fam. 1.--_Oleacinidae._ Shell oval, elongated, with narrow aperture; neck very long; labial palps prominent. _Oleacina (Glandina). Streptostyla._

Fam. 2.--_Testacellidae._ Shell globular or auriform, external or partly covered by the mantle. _Streptaxis. Gibbulina. Aerope. Rhytida. Daudebardia. Testacella. Chlamydophorus. Schizoglossa._

Fam. 3.--_Rathouisiidae._ No shell, a carinated mantle covering the whole body; male and female apertures distant, the female near the anus. _Rathouisia. Atopos._

Tribe 3.--ELASMOGNATHA. Jaw with a well-developed dorsal appendage.

Fam. 1.--_Succineidae._ Anterior tentacles much reduced; male and female apertures contiguous but distinct; shell thin, spiral, with short spire. _Succinea_, British. _Homalonyx. Hyalimax. Neohyalimax._

Fam. 2.--_Janellidae._ Limaciform, with internal rounded shell; mantle very small and triangular; pulmonary chamber with tracheae; no anterior tentacles. _Janella. Aneitella. Aneitea. Triboniophorus._

Tribe 4.--DITREMATA. Male and female apertures distant.

Fam. 1.--_Vaginulidae._ No shell; limaciform; terrestrial; female aperture on right side in middle of body; anus posterior. _Vaginula._

Fam. 2.--_Oncidiidae._ No shell; limaciform; littoral; female aperture posterior, near anus; a reduced pulmonary cavity with a distinct aperture. _Oncidium. Oncidiella_, British. _Peronia._

AUTHORITIES.--L. Boutan, "La Cause principale de l'asymétrie des mollusques gastéropodes," _Arch. de zool. expér._ (3), vii. (1899); A. Lang, "Versuch einer Erklärung der Asymmetrie der Gastropoder," _Vierteljahrsschr. naturforsch. Gesellschaft_, Zürich, 36 (1892); A. Robert, "Recherches sur le développement des Troques," _Arch. de zool. expér._ (3), x. (1903); P. Pelseneer, "Report on the Pteropoda," _Zool. "Challenger" Expedit._ pts. lviii., lxv., lxvi. (1887, 1888); P. Pelseneer, "Protobranches aériens et Pulmonés branchifères," _Arch. de biol._ xiv. (1895); W.A. Herdman, "On the Structure and Functions of the Cerata or Dorsal Papillae in some Nudibranchiate Mollusca," _Quart. Journ. Mic. Sci._ (1892); J.T. Cunningham, "On the Structure and Relations of the Kidney in Aplysia," _Mitt. Zool. Stat. Neapel_, iv. (1883); Böhmig, "Zur feineren Anatomie von _Rhodope veranyi_, Kölliker," _Zeitschr. f. wiss. Zool._ vol. lvi. (1893).

TREATISES.--S.P. Woodward, _Manual of the Mollusca_ (2nd ed., with appendix, London, 1869); E. Forbes and S. Hanley, _History of British Mollusca_ (4 vols., London, 1853); Alder and Hancock, _Monograph of British Nudibranchiate Mollusca_ (London, Roy. Society, 1845); P. Pelseneer, _Mollusca. Treatise on Zool._, edited by E. Ray Lankester, pt. v. (1906); E. Ray Lankester, "Mollusca," in 9th ed. of this Encyclopaedia, to which this article is much indebted. (J. T. C)

GASTROTRICHA, a small group of fairly uniform animals which live among Rotifers and Protozoa at the bottom of ponds and marshes, biding amongst the recesses of the algae and sphagnum and other fresh-water plants and eating organic débris and Infusoria. They are of minute size varying from one-sixtieth to one-three-hundredth of an inch, and they move by means of long cilia. Two ventral bands composed of regular transverse rows of cilia are usually found. The head bears some especially large cilia. The cuticle which covers the body is here and there raised into overlapping scales which may be prolonged into bristles. An enlarged, frontal scale may cover the head, and a row of scales separates the ventral ciliated areas from one another, whilst two series of alternating rows cover the back and side. The body, otherwise circular in section, is slightly flattened ventrally. The mouth is anterior and slightly ventral; it leads into a protrusible pharynx armed with recurved teeth that can be everted. This leads to a muscular oesophagus with a triradiate lumen, which acts as a sucking pump and ends in a funnel-valve projecting into the stomach. The last named is oval and formed of four rows of large cells; it is separated by a sphincter from the rectum, which opens posteriorly and dorsally. The nitrogenous excretory apparatus consists of a coiled tube on each side of the stomach; internally the tubes end in large flame-cells, and externally by small pores which lie on the edges of the ventral row of scales. A cerebral ganglion rests on the oesophagus and supplies the cephalic cilia and hairs; it is continued some way back as two dorsal nerve trunks. The sense organs are the hairs and bristles and in some species eyes. The muscles are simple and unstriated and for the most part run longitudinally.

The two ovaries lie at the level of the juncture of the stomach and rectum. The eggs become very large, sometimes half the length of the mother; they are laid amongst water weeds. The male reproductive system is but little known, a small gland lying between the ovaries has been thought to be a testis, and if it be, the Gastrotricha are hermaphrodite.

Zelinka classifies the group as follows:--

Sub-order 1.--EUICHTHYDINA with a forked tail.

(i.) Fam. Ichthydidae, without bristles. Genera: _Ichthydium, Lepidoderma_.

(ii.) Fam. Chaetonotidae, with bristles. Genera: _Chaetonotus, Chaetura_.

Sub-order 2.--APODINA, tail not forked. Genera: _Dasydytes, Gossea, Stylochaeta_.

The genus _Aspidiophorus_ recently described by Voigt seems in some respects intermediate between _Lepidoderma_ and _Chaetonotus_. _Zelinkia_ and _Philosyrtis_ are two slightly aberrant forms described by Giard from certain diatomaceous sands. Altogether there must be some forty to fifty described species.

The group is an isolated one and shows no clear affinities with any of the great phyla. Those that are usually dwelt on are treated with the Rotifers and Nematoda and Turbellaria.

LITERATURE.--A.C. Stokes, _The Microscope_ (Detroit, 1887-1888); C. Zelinka, _Zeitschr. wiss. Zool._ xlix., 1890, p. 209; M. Voigt, _Forschber. Plön._ Th. ix., 1904, p. 1; A. Giard, _C. R. Soc. Biol._ lvi. pp. 1061 and 1063; E. Daday, _Termes. Fuzetek._ xxiv. p. 1; F. Zschokke, _Denk. Schweiz. Ges._ xxxvii. p. 109; S. Hlava, _Zool. Anz._ xxviii., 1905, p. 331. (A. E. S.)

GATAKER, THOMAS (1574-1654), English divine, was born in London in September 1574, and educated at St John's College, Cambridge. From 1601 to 1611 he held the appointment of preacher to the society of Lincoln's Inn, which he resigned on accepting the rectory of Rotherhithe. In 1642 he was chosen a member of the assembly of divines at Westminster, and annotated for that assembly the books of Isaiah, Jeremiah and Lamentations. He disapproved of the introduction of the Covenant, and declared himself in favour of episcopacy. He was one of the forty-seven London clergymen who disapproved of the trial of Charles I. He was married four times, and died in July 1654.

His principal works, besides some volumes of sermons are--_On the Nature and Use of Lots_ (1619), a curious treatise which led to his being accused of favouring games of chance; _Dissertatio de stylo Novi Testamenti_ (1648); _Cinnus, sive Adversaria miscellanea, in quibus Sacrae Scripturae primo, deinde aliorum scriptorum, locis aliquam multis lux redditur_ (1651), to which was afterwards subjoined _Adversaria Posthuma_; and his edition of _Marcus Antoninus_ (1652), which, according to Hallam, is the "earliest edition of any classical writer published in England with original annotations," and, for the period at which it was written, possesses remarkable merit. His collected works were published at Utrecht in 1698.

GATCHINA, a town of Russia, in the government of St Petersburg, 29 m. by rail S. of the city of St Petersburg, in 59° 34' N. and 30° 6' E. Pop. (1860) 9184; (1897) 14,735. It is situated in a flat, well-wooded, and partly marshy district, and on the south side of the town are two lakes. Among its more important buildings are the imperial palace, which was founded in 1770 by Prince Orlov, and constructed according to the plans of the Italian architect Rinaldi; a military orphanage, founded in 1803; and a school for horticulture. Among the few industrial establishments is a porcelain factory. At Gatchina an alliance was concluded between Russia and Sweden on the 29th of October 1799.

GATE, an opening into any enclosure for entrance or exit, capable of being closed by a barrier at will. The word is of wide application, embracing not only the defensive entrance ways into a fortified place, with which this article mainly deals, or the imposing architectural features which form the main entrances to palaces, colleges, monastic buildings, &c., but also the common five-barred barrier which closes an opening into a field. The most general distinction that can be made between "door" and "gate" is that of size, the greater entrance into a court containing other buildings being the "gate," the smaller entrances opening directly into the particular buildings the "doors," or that of construction, the whole entrance way being a "gate" or gateway, the barrier which closes it a "door." A further distinction is drawn by applying "door" to the solid barriers or "valves" of wood, metal, &c., made in panels and fitted to a framework, and "gate" to an openwork structure, whether of metal or wood (see further DOOR and METAL-WORK). The ultimate origin of the word is obscure; the early forms appear with a palatalized initial letter, still surviving in such dialectical forms as "yate," or in Scots "yett." It is probably connected with the root of "get," in the sense either of "means of access" or of "holding," "receptacle"; cf. Dutch _gat_, hole. There may be a connexion, however, with "gate," now usually spelled "gait," a manner of walking,[1] but originally a way, passage; cf. Ger. _Gasse_, narrow street, lane.

The entrance through the enclosing walls of a city or fortification has been from the earliest times a place of the utmost importance, considered architecturally, socially or from the point of view of the military engineer. In the East the "gate" was and still is in many Mahommedan countries the central place of civic life. Here was the seat of justice and of audience, the most important market-place, the spot where men gathered to receive and exchange news. The references in the Bible to the gates of the city in all these varied aspects are innumerable (cf. Gen. xix. 1; Deut. xxv. 7; Ruth iv. 1; 2 Sam. xix. 8; 2 Kings vii. 1). Later the seat of justice and of government is transferred to the gate of the palace of the king (cf. Dan. ii. 49, and Esther ii. 19), and this use is preserved to-day in the official title of the seat of government of the Turkish empire at Constantinople, the "Sublime Porte," a translation of the Turkish _Bab Aliy_ (_bab_, gate, and _aliy_, high). A full account with many modern instances of Eastern customs will be found in Sir Charles Warren's article "Gate" in Hastings's _Dict. of Bible_. For the "pylon," the typical gate of Egyptian architecture, see ARCHITECTURE.

The gates into a walled town or other fortified place were necessarily in early times the chief points on which the attack concentrated, and the features, common throughout the ages, of flanking or surmounting towers and of galleries over the entrance way, are found in the Assyrian gate at Khorsabad (cf. 2 Chron. xxvi. 9; 2 Sam. xviii. 24). With the coming of peaceful times to a city or the removal of the fear of sudden attack, the gateways would take a form adapted more for ready exit and entrance than for defence, though the possibility of defending them was not forgotten. Such city gates often had separate openings for entrance and exit, and again for foot passengers and for vehicles. The Gallo-Roman gate at Autun has four entrances, two just wide enough to admit carriages, and two narrow alleys for foot passengers. A fine example of a Roman city gate, dating from the time of Constantine, is at Trèves. It is four storeys high, with ornamental windows, and decorated with columns on each storey. The two outer wings project beyond the central part, the two entrance ways are 14 ft. wide, and could be closed by doors and a portcullis. The chambers in the storeys above were used for the purposes of civil administration. In more modern times city gateways have often followed the type of the Roman triumphal arch, with a single wide opening and purely ornamental superstructure. On the other hand, the defensive gate formed by an archway entering as it were through a tower has been constantly followed as a type of entrance to buildings of an entirely peaceful character. A fine example of such a gateway, originally built for defence, is at Battle Abbey; this was built by Abbot Retlynge in 1338, when Edward III. granted a licence to fortify and crenellate the abbey. Such gateways are typical of Tudor palaces, as at St James's or at Hampton Court, and are the most common form in the colleges of Oxford and Cambridge. The Tom Gate at Christ Church, Oxford, with its surmounted domed bell tower, or the cupola resting on columns at Queen's College, Oxford, are further examples of the gate architecturally considered.

The changes the fortified gateway has undergone in construction and the varying relative importance it has held in the scheme of defence follow the lines of development taken by the history of FORTIFICATION AND SIEGECRAFT (q.v.). The following is a short sketch of the main stages in its history. A good example of the Roman fortified city gate still remains at Pompeii. Here there is one passage way for vehicles, 14 ft. wide; this is open to the sky. The two footways on either side are arched, with openings in the centre on to the central way. The doors of the gate are on the city side, but a portcullis (_cataracta_) closed it on the country side. The gateways of the Roman permanent camps (_castra stativa_) were four in number, the _porta praetoria_ and _Decumana_ at either end, with _principalis dextra_ and _sinistra_ on the side (see also CAMP). At Pevensey (_Anderida_) a small postern on the north side of the Roman walls was laid bare in 1906-1907, in which the passage curves in the thickness of the wall, and from a width admitting two men abreast narrows so that one alone could block it. Flanking towers or bastions guarded the main entrances, while in front were built outworks, of palisades, &c., to protect it; these were known as _procastra_ or _antemuralia_, and the entrances to these were placed so that they could be flanked from the main walls.

In the defence of a fortified place the gate had not only to be protected from sudden surprise, but also had to undergo protracted attacks concentrated upon it during a siege. Thus until the coming of gunpowder, the ingenuity of military engineers was exhausted in accumulating the most complicated defences round the gateways, and the strength of a fortified place could be estimated by the fewness of its gates. Viollet-le-Duc (_Dict. de l'arch. du moyen âge_, s.v. _Porte_) takes the Narbonne and Aude gates (E. and W.) of Carcassonne as typical instances of this complication. The following brief account of the Narbonne Gate (fig. 1), one of the principal parts of the work on the fortifications begun by Philip the Bold in 1285, will give some idea of the varied means of defence, which may be found individually if not always in such collective abundance in the fortified gateways of the middle ages. Two massive towers flanked the actual entrance and were linked across by an iron chain; over the entrance (E) was a machicolation, further added to in time of war by a hoarding of timber; and an outer portcullis fell in front of the heavy iron-lined doors. On to the passage way between the first and second doors opened a square machicolation (G) from which the defenders in the upper chambers of the gate could attack an enemy that had succeeded in breaking through the first entrance or had been trapped by the falling of the first portcullis. Another machicolation (I) opened from the roof in front of the second portcullis and second door. So much for the gate itself; but before an attack could reach that point, the following defences had to be passed: an immense circular barbican (A) protected the entrance across the moat and through the outer _enceinte_ of the city. This entrance was flanked by a masked return of the wall (C), while palisades (P) still further hampered the assailant in his passage across the "lists" to the foot of the gate towers. Here sappers would find themselves exposed to a fire from the loopholes and from the machicolated hoardings above them, while the projecting horns with which the face of the towers terminated forced them to uncover themselves to a flanking fire from the indents in the main curtain on either side of the towers.

The later history of the gateway is merged in that of modern fortification. The more elaborate the gate defences the greater was the inducement for the besieger to attack the walls, and improvements in methods of siegecraft ultimately compelled the defender to develop the _enceinte_ from its medieval form of a ring wall with flanking towers to the 17th century form of bastions, curtains, tenailles and ravelins, all intimately connected in one general scheme of defence. By Vauban's time there is little to distinguish the position and defences of the gateways from the rest of the fortifications surrounding a town. A road from the country usually entered one of the ravelins, sinking into the glacis, crossing the ditch of the ravelin and piercing the parapet almost at right angles to its proper direction (see fig. 2, which also shows a typical arrangement of minor communications such as ramps and staircases). From the interior of the ravelin it passed across the main ditch to a gate in the curtain of the enceinte. The road was in fact artificially made to wind in such a way that it was kept under fire from the defences throughout, while the part of it inside the works was bent so as to place a covering mass between the enemy's fire and troops using the road for a sortie. Thus the gate itself was merely a barrier against a _coup de main_ and to keep out unauthorized persons. In conditions precluding the making of a breach in the walls, i.e. in surprises and assaults _de vive force_, the gateway and accompanying drawbridge continue to play their part in the 16th, 17th and 18th centuries, but they seldom or never appear as the objectives of a siege _en règle_. In Vauban's works, and those of most other engineers, there was generally a postern giving access to the floor of the main ditch, in the centre of the curtain escarp. The gates of Vauban's and later fortresses are strong heavy wooden doors, and the gateways more or less ornamental archways, exactly as in many private mansions of castellar form. In modern fortresses the gate of a detached fort or an _enceinte de sureté_ is intended purely as a defence against an unexpected rush. The usual method is to have two gates, the outer one a lattice or portcullis of iron bars and the inner one a plate of half-inch steel armour, backed by wood and loopholed. The defenders of the gate can by this arrangement fire from the inner loopholes through the outer gate upon the approaches, and also keep the enemy under fire whilst he is trying to force the outer gate itself. The ditches are crossed either by drawbridges or by ramps leading the road down to the floor of the ditch.

The "gate" as a barrier to be removed and as an entrance to be passed is of constant occurrence in figurative language and in symbolical usage. The gates of the temple of Janus (q.v.) at Rome stood open in war and closed in peace. The _pylon_ of ancient Egypt had a symbolical meaning in the Book of the Dead, and religious significance attaches to the _torii_, one of the outward signs of the Shinto religion in Japan, the Buddhist _toran_, and to the Chinese _pai-loo_, the honorific gateways erected to ancestors. The gates of heaven and hell, the gates of death and darkness, the wide and narrow gates that lead to destruction and life (Matt. vii. 13 and 14), are familiar metaphorical phrases in the Bible. In Greek and Roman legend dreams pass through gates of transparent horn if true, if deceptive and false through opaque gates of ivory (Hom. _Od_. xix. 560 sq.; Virg. _Aen_. vi. 893). (C. We.)

FOOTNOTE:

[1] The spelling "gait" is confined to this meaning--the only literary one surviving. In the form "gate" it appears dialectally in this sense and in such particular meanings as a right to run cattle on common or private ground or as a passage way in mines. The principal survival is in names of streets in the north and midlands of England and in Scotland, e.g. Briggate at Leeds, Wheeler Gate and Castle Gate at Nottingham, Gallow Tree Gate at Leicester, and Canongate and Cowgate at Edinburgh.

GATEHOUSE. In the second half of the 16th century in England the entrance gateway, which formed part of the principal front of the earlier feudal castles, became a detached feature attached to the mansions only by a wall enclosing the entrance court. The gatehouse then constituted a structure of some importance, and included sometimes many rooms as at Stanway Hall, Gloucestershire, where it measures 44 ft. by 22 ft. and has three storeys; at Westwood, Worcestershire, it had a frontage of 54 ft. with two storeys; and at Burton Agnes, Yorkshire, it was still larger and was flanked by great octagonal towers at the angles and had three storeys. At a later period smaller accommodation was provided so that it virtually became a lodge, but being designed to harmonize with the mansion it presented sometimes a monumental structure. On the continent of Europe the gatehouse forms a much more important building, as it formed part of the town fortifications, where it sometimes defended the passage of a bridge across the stream or moat. There are numerous examples in France and Germany.

GATES, HORATIO (1728-1806), American general, was born at Maldon in Essex, England, in 1728. He entered the English army at an early age, and was rapidly promoted. He accompanied General Braddock in his disastrous expedition against Fort Duquesne in 1755, and was severely wounded in the battle of July 9; and he saw other active service in the Seven Years' War. After the peace of 1763 he purchased an estate in Virginia, where he lived till the outbreak of the War of Independence in 1775, when he was named by Congress adjutant-general. In 1776 he was appointed to command the troops which had lately retreated from Canada, and in August 1777, as a result of a successful intrigue, was appointed to supersede General Philip Schuyler in command of the Northern Department. In the two battles of Saratoga (q.v.) his army defeated General Burgoyne, who, on the 17th of October, was forced to surrender his whole army. This success was, however, largely due to the previous manoeuvres of Schuyler and to Gates's subordinate officers. The intrigues of the Conway Cabal to have Washington superseded by Gates completely failed, but Gates was president for a time of the Board of War, and in 1780 was placed in chief command in the South. He was totally defeated at Camden, S. C., by Cornwallis on the 17th of August 1780, and in December was superseded by Greene, though an investigation into his conduct terminated in acquittal (1782). He then retired to his Virginian estate, whence he removed to New York in 1790, after emancipating his slaves and providing for those who needed assistance. He died in New York on the 10th of April 1806.

GATESHEAD, a municipal, county and parliamentary borough of Durham, England; on the S. bank of the Tyne opposite Newcastle, and on the North Eastern railway. Pop. (1891) 85,692; (1901) 109,888. Though one of the largest towns in the county, neither its streets nor its public buildings, except perhaps its ecclesiastical buildings, have much claim to architectural beauty. The parish church of St Mary is an ancient cruciform edifice surmounted by a lofty tower; but extensive restoration was necessitated by a fire in 1854 which destroyed a considerable part of the town. The town-hall, public library and mechanic's institute are noteworthy buildings. Education is provided by a grammar school, a large day school for girls, and technical and art schools. There is a service of steam trams in the principal streets, and three fine bridges connect the town with Newcastle-upon-Tyne. There are large iron works (including foundries and factories for engines, boilers, chains and cables), shipbuilding yards, glass manufactories, chemical, soap and candle works, brick and tile works, breweries and tanneries. The town also contains a depot of the North Eastern railway, with large stores and locomotive works. Extensive coal mines exist in the vicinity; and at Gateshead Fell are large quarries for grindstones, which are much esteemed and are exported to all parts of the world. Large gas-works of the Newcastle and Gateshead Gas Company are also situated in the borough. The parliamentary borough returns one member. The corporation consists of a mayor, 9 aldermen, and 27 councillors. Area, 3132 acres.

Gateshead (Gateshewed) probably grew up during late Saxon times, the mention of the church there in which Bishop Walcher was murdered in 1080 being the first evidence of settlement. The borough probably obtained its charter during the following century, for Hugh de Puiset, bishop of Durham (1153-1195), confirmed to his burgesses similar rights to those of the burgesses of Newcastle, freedom of toll within the palatinate and other privileges. The bishop had a park here in 1348, and in 1438 Bishop Nevill appointed a keeper of the "tower." The position of the town led to a struggle with Newcastle over both fishing and trading rights. An inquisition of 1322 declared that the water of the Tyne was divided into three parts: the northern, belonging to Northumberland; the southern to Durham; and the central, common to all. At another inquisition held in 1336 the men of Gateshead claimed liberty of trading and fishing along the coast of Durham, and freedom to sell their fish where they would. In 1552, on the temporary extinction of the diocese of Durham, Gateshead was attached to Newcastle, but in 1554 was regranted to Bishop Tunstall. As compensation the bishop granted to Newcastle, at a nominal rent, the Gateshead salt-meadows, with rights of way to the High Street, thus abolishing the toll previously paid to the bishop. During the next century Bishop Tunstall's successors incorporated nearly all the various trades of Gateshead, and Cromwell continued this policy. The town government during this period was by the bishop's bailiff, and the holders of the burgages composed the juries of the bishop's courts leet and baron. No charter of incorporation is extant, but in 1563 contests were carried on under the name of the bailiffs, burgesses and commonalty, and a list of borough accounts exists for 1696. The bishop appointed the last borough bailiff in 1681, and though the inhabitants in 1772 petitioned for a bailiff the town remained under a steward and grassmen until the 19th century. As part of the palatinate of Durham, Gateshead was not represented in parliament until 1832. At the inquisition of 1336 the burgesses claimed an annual fair on St Peter's Day, and depositions in 1577 mention a borough market held on Tuesday and Friday, but these were apparently extinct in Camden's day, and no grant of them is extant. The medieval trade seems to have centred round the fisheries and the neighbouring coal mines which are mentioned in 1364 and also by Leland.

GATH, one of the five chief cities of the Philistines. It is frequently mentioned in the historical books of the Old Testament, and from Amos vi. 2 we conclude that, like Ashdod, it fell to Sargon in 711. Its site appears to have been known in the 4th century, but the name is now lost. Eusebius (in the _Onomasticon_) places it near the road from Eleutheropolis (Beit Jibrïn) to Diospolis (Ludd) about five Roman miles from the former. The Roman road between these two towns is still traceable, and its milestones remain in places. East of the road at the required distance rises a white cliff, almost isolated, 300 ft. high and full of caves. On the top is the little mud village of Tell es-Safi ("the shining mound"), and beside the village is the mound which marks the site of the Crusaders' castle of Blanchegarde (Alba Custodia), built in 1144. Tell es-Safi was known by its present name as far back as the 12th century; but it appears not improbable that the strong site here existing represents the ancient Gath. The cliff stands on the south side of the mouth of the Valley of Elah, and Gath appears to have been near this valley (1 Sam. xvii. 2, 52). This identification is not certain, but it is at least much more probable than the theory which makes Gath, Eleutheropolis, and Beit Jibrïn one and the same place. The site was partially excavated by the Palestine Exploration Fund in 1899, and remains extending in date back to the early Canaanite period were discovered.

GATLING, RICHARD JORDAN (1818-1903), American inventor, was born in Hertford county, North Carolina, on the 12th of September 1818. He was the son of a well-to-do planter and slave-owner, from whom he inherited a genius for mechanical invention and whom he assisted in the construction and perfecting of machines for sowing cotton seeds, and for thinning the plants. He was well educated and was successively a school teacher and a merchant, spending all his spare time in developing new inventions. In 1839 he perfected a practical screw propeller for steamboats, only to find that a patent had been granted to John Ericsson for a similar invention a few months earlier. He established himself in St Louis, Missouri, and taking the cotton-sowing machine as a basis he adapted it for sowing rice, wheat and other grains, and established factories for its manufacture. The introduction of these machines did much to revolutionize the agricultural system in the country. Becoming interested in the study of medicine through an attack of smallpox, he completed a course at the Ohio Medical College, taking his M.D. degree in 1850. In the same year he invented a hemp-breaking machine, and in 1857 a steam plough. At the outbreak of the Civil War he was living in Indianapolis, and devoted himself at once to the perfecting of fire-arms. In 1861 he conceived the idea of the rapid fire machine-gun which is associated with his name. By 1862 he had succeeded in perfecting a gun that would discharge 350 shots per minute; but the war was practically over before the Federal authorities consented to its official adoption. From that time, however, the success of the invention was assured, and within ten years it had been adopted by almost every civilized nation. Gatling died in New York City on the 26th of February 1903.

GATTY, MARGARET (1809-1873), English writer, daughter of the Rev. Alexander Scott (1768-1840), chaplain to Lord Nelson, was born at Burnham, Essex, in 1809. She early began to draw and to etch on copper, being a regular visitor to the print-room of the British Museum from the age of ten. She also illuminated on vellum, copying the old strawberry borders and designing initials. In 1839 Margaret Scott married the Rev. Alfred Gatty, D.D., vicar of Ecclesfield near Sheffield, subdean of York cathedral, and the author of various works both secular and religious. In 1842 she published in association with her husband a life of her father; but her first independent work was _The Fairy Godmother and other Tales_, which appeared in 1851. This was followed in 1855 by the first of five volumes of _Parables from Nature_, the last being published in 1871. It was under the _nom de plume_ of Aunt Judy, as a pleasant and instructive writer for children, that Mrs Gatty was most widely known. Before starting _Aunt Judy's Magazine_ in May 1866, she had brought out _Aunt Judy's Tales_ (1858) and _Aunt Judy's Letters_ (1862), and among the other children's books which she subsequently published were _Aunt Judy's Song Book for Children_ and _The Mother's Book of Poetry_. "Aunt Judy" was the nickname given by her daughter Juliana Horatia Ewing (q.v.). The editor of the magazine was on the friendliest terms with her young correspondents and subscribers, and her success was largely due to the sympathy which enabled her to look at things from the child's point of view. Besides other excellences her children's books are specially characterized by wholesomeness of sentiment and cheerful humour. Her miscellaneous writings include, in addition to several volumes of tales, _The Old Folks from Home_, an account of a holiday ramble in Ireland; _The Travels and Adventures of Dr Wolff the Missionary_ (1861), an autobiography edited by her; _British Sea Weeds_ (1862); _Waifs and Strays of Natural History_ (1871); _A Book of Emblems_ and _The Book of Sun-Dials_ (1872). She died at Ecclesfield vicarage on the 4th of October 1873.

GAU, JOHN (c. 1495-? 1553), Scottish translator, was born at Perth towards the close of the 15th century. He was educated in St Salvator's College at St Andrews. He appears to have been in residence at Malmö in 1533, perhaps as chaplain to the Scots community there. In that year John Hochstraten, the exiled Antwerp printer, issued a book by Gau entitled: _The Richt vay to the Kingdome of Heuine_, of which the chief interest is that it is the first Scottish book written on the side of the Reformers. It is a translation of Christiern Pedersen's _Den rette vey till Hiemmerigis Rige_ (Antwerp, 1531), for the most part direct, but showing intimate knowledge in places of the German edition of Urbanus Rhegius. Only one copy of Gau's text is extant, in the library of Britwell Court, Bucks. It has been assumed that all the copies were shipped from Malmö to Scotland, and that the cargo was intercepted by the Scottish officers on the look out for the heretical works which were printed abroad in large numbers. This may explain the silence of all the historians of the Reformed Church--Knox, Calderwood and Spottiswood. Gau married in 1536 a Malmö citizen's daughter, bearing the Christian name Birgitta. She died in 1551, and he in or about 1553.

The first reference to the _Richt Vay_ appeared in Chalmers's _Caledonia_, ii. 616. Chalmers, who was the owner of the unique volume before it passed into the Britwell Court collection, considered it to be an original work. David Laing printed extracts for the Bannatyne Club (_Miscellany_, iii., 1855). The evidence that the book is a translation was first given by Sonnenstein Wendt in a paper "Om Reformatorerna i Malmö," in Rördam's _Ny Kirkehistoriske Samlinger_, ii. (Copenhagen, 1860). A complete edition was edited by A.F. Mitchell for the Scottish Text Society (1888). See also Lorimer's _Patrick Hamilton_.

GAUDEN, JOHN (1605-1662), English bishop and writer, reputed author of the _Eikon Basilike_, was born in 1605 at Mayland, Essex, where his father was vicar of the parish. Educated at Bury St Edmunds school and at St John's College, Cambridge, he took his M.A. degree in 1625/6. He married Elizabeth, daughter of Sir William Russell of Chippenham, Cambridgeshire, and was tutor at Oxford to two of his wife's brothers. He seems to have remained at Oxford until 1630, when he became vicar of Chippenham. His sympathies were at first with the parliamentary party. He was chaplain to Robert Rich, second earl of Warwick, and preached before the House of Commons in 1640. In 1641 he was appointed to the rural deanery of Bocking. Apparently his views changed as the revolutionary tendency of the Presbyterian party became more pronounced, for in 1648/9 he addressed to Lord Fairfax _A Religious and Loyal Protestation_ ... against the proceedings of the parliament. Under the Commonwealth he faced both ways, keeping his ecclesiastical preferment, but publishing from time to time pamphlets on behalf of the Church of England. At the Restoration he was made bishop of Exeter. He immediately began to complain to Hyde, earl of Clarendon, of the poverty of the see, and based claims for a better benefice on a certain secret service, which he explained on the 20th of January 1661 to be the sole invention of the _Eikon Basilike, The Pourtraicture of his sacred Majestie in his Solitudes and Sufferings_ put forth within a few hours after the execution of Charles I. as written by the king himself. To which Clarendon replied that he had been before acquainted with the secret and had often wished he had remained ignorant of it. Gauden was advanced in 1662, not as he had wished to the see of Winchester, but to Worcester. He died on the 23rd of May of the same year.

The evidence in favour of Gauden's authorship rests chiefly on his own assertions and those of his wife (who after his death sent to her son John a narrative of the claim), and on the fact that it was admitted by Clarendon, who should have had means of being acquainted with the truth. Gauden's letters on the subject are printed in the appendix to vol. iii. of the _Clarendon Papers_. The argument is that Gauden had prepared the book to inspire sympathy with the king by a representation of his pious and forgiving disposition, and so to rouse public opinion against his execution. In 1693 further correspondence between Gauden, Clarendon, the duke of York, and Sir Edward Nicholas was published by Mr Arthur North, who had found them among the papers of his sister-in-law, a daughter-in-law of Bishop Gauden; but doubt has been thrown on the authenticity of these papers. Gauden stated that he had begun the book in 1647 and was entirely responsible for it. But it is contended that the work was in existence at Naseby,[1] and testimony to Charles's authorship is brought forward from various witnesses who had seen Charles himself occupied with it at various times during his imprisonment. It is stated that the MS. was delivered by one of the king's agents to Edward Symmons, rector of Raine, near Bocking, and that it was in the handwriting of Oudart, Sir Edward Nicholas's secretary. The internal evidence has, as is usual in such cases, been brought forward as a conclusive argument in favour of both contentions. Doubt was thrown on Charles's authorship in Milton's _Eikonoklastes_ (1649), which was followed almost immediately by a royalist answer, _The Princely Pelican. Royall Resolves--Extracted from his Majesty's Divine Meditations, with satisfactory reasons ... that his Sacred Person was the only Author of them_ (1649). The history of the whole controversy, which has been several times renewed, was dealt with in Christopher Wordsworth's tracts in a most exhaustive way. He eloquently advocated Charles's authorship. Since he wrote in 1829, some further evidence has been forthcoming in favour of the Naseby copy. A correspondence relating to the French translation of the work has also come to light among the papers of Sir Edward Nicholas. None of the letters show any doubt that King Charles was the author. S.R. Gardiner (_Hist. of the Great Civil War_, iv. 325) regards Mr Doble's articles in the _Academy_ (May and June 1883) as finally disposing of Charles's claim to the authorship, but this is by no means the attitude of other recent writers. If Gauden was the author, he may have incorporated papers, &c., by Charles, who may have corrected the work and thus been joint-author. This theory would reconcile the conflicting evidence, that of those who saw Charles writing parts and read the MS. before publication, and the deliberate statements of Gauden.

See also the article by Richard Hooper in the _Dict. Nat. Biog._; Christopher Wordsworth, _Who wrote Eikon Basilike?_ two letters addressed to the archbishop of Canterbury (1824), and _King Charles the First, the Author of Icon Basilikè_ (1828); H.J. Todd, _A Letter to the Archbishop of Canterbury concerning Eikon Basilike_ (1825); _Bishop Gauden, The Author of the Icôn Basilikè_ (1829); W.G. Broughton, _A Letter to a Friend_ (1826), _Additional Reasons ..._ (1829), supporting the contention in favour of Dr Gauden; Mr E.J.L. Scott's introduction to his reprint (1880) of the original edition; articles in the _Academy_, May and June 1883, by Mr C.E. Doble; another reprint edited by Mr Edward Almack for the King's Classics (1904); and Edward Almack, _Bibliography of the King's Book_ (1896). This last book contains a summary of the arguments on either side, a full bibliography of works on the subject, and facsimiles of the title pages, with full descriptions of the various extant copies.

FOOTNOTE:

[1] See a note in Archbishop Tenison's handwriting in his copy of the _Eikon Basilike_ preserved at Lambeth Palace, and quoted in Almack's _Bibliography_, p. 15.

GAUDICHAUD-BEAUPRÉ, CHARLES (1789-1854), French botanist, was born at Angoulême on the 4th of September 1789. He studied pharmacy first in the shop of a brother-in-law at Cognac, and then under P.J. Robiquet at Paris, where from R.L. Desfontaines and L.C. Richard he acquired a knowledge of botany. In April 1810 he was appointed dispenser in the military marine, and from July 1811 to the end of 1814 he served at Antwerp. In 1817 he joined the corvette "Uranie" as pharmaceutical botanist to the circumpolar expedition commanded by D. de Freycinet. The wreck of the vessel on the Falkland Isles, at the close of 1819, deprived him of more than half the botanical collections he had made in various parts of the world. In 1830-1833 he visited Chile, Peru and Brazil, and in 1836-1837 he acted as botanist to "La Bonite" during its circumnavigation of the globe. His theory accounting for the growth of plants by the supposed coalescence of elementary "phytons" involved him, during the latter years of his life, in much controversy with his fellow-botanists, more especially C.F.B. de Mirbel. He died in Paris on the 16th of January 1854.

Besides accounts of his voyages round the world, Gaudichaud-Beaupré wrote "Lettres sur l'organographie et la physiologie," _Arch. de botanique_, ii., 1883; "Recherches générales sur l'organographie," &c. (prize essay, 1835), _Mém. de l'Académie des Sciences_, t. viii. and kindred treatises, with memoirs on the potato-blight, the multiplication of bulbous plants, the increase in diameter of dicotyledonous plants, and other subjects; and _Réfutation de toutes les objections contre les nouveaux principes physiologiques_ (1852).

GAUDRY, JEAN ALBERT (1827-1908), French geologist and palaeontologist, was born at St Germain-en-Laye on the 16th of September 1827, and was educated at the college, Stanislas. At the age of twenty-five he made explorations in Cyprus and Greece, residing in the latter country from 1855 to 1860. He then investigated the rich deposit of fossil vertebrata at Pikermi and brought to light a remarkable mammalian fauna, Miocene in age, and intermediate in its forms between European, Asiatic and African types. He also published an account of the geology of the island of Cyprus (_Mém. Soc. Géol. de France_, 1862). In 1853, while still in Cyprus, he was appointed assistant to A. d'Orbigny, who was the first to hold the chair of palaeontology in the museum of natural history at Paris. In 1872 he succeeded to this important post; in 1882 he was elected member of the Academy of Sciences; and in 1900 he presided over the meetings of the eighth International Congress of Geology then held in Paris. He died on the 27th of November 1908. He is distinguished for his researches on fossil mammalia, and for the support which his studies have rendered to the theory of evolution.

PUBLICATIONS.--_Animaux fossiles et géologie de l'Attique_ (2 vols., 1862-1867); _Cours de paléontologie_ (1873); _Animaux fossiles du Mont Lebéron_ (1873); _Les Enchaînements du monde animal dans les temps géologiques_ (_Mammifères Tertiaires_, 1878; _Fossiles primaires_, 1883; _Fossiles secondaires_, 1890); _Essai de paléontologie philosophique_ (1896). Brief memoir with portrait in _Geol. Mag._ (1903), p. 49. (H. B. W.)

GAUDY, an adjective meaning showy, very bright, gay, especially with a sense of tasteless or vulgar extravagance, of colour or ornament. The accurate origin of the various senses which this word and the substantive "gaud" have taken are somewhat difficult to trace. They are all ultimately to be referred to the Lat. _gaudere_, to rejoice, _gaudium_, joy, some of them directly, others to the French derivative _gaudir_, to rejoice, and O. Fr. _gaudie_. As a noun, in the sense of rejoicing or feast, "gaudy" is still used of a commemoration dinner at a college at the university of Oxford. "Gaud," meaning generally a toy, a gay adornment, a piece of showy jewelry, is more specifically applied to larger and more decorative beads in a rosary.

GAUERMANN, FRIEDRICH (1807-1862), Austrian painter, son of the landscape painter Jacob Gauermann (1773-1843), was born at Wiesenbach near Gutenstein in Lower Austria on the 20th of September 1807. It was the intention of his father that he should devote himself to agriculture, but the example of an elder brother, who, however, died early, fostered his inclination towards art. Under his father's direction he began studies in landscape, and he also diligently copied the works of the chief masters in animal painting which were contained in the academy and court library of Vienna. In the summer he made art tours in the districts of Styria, Tirol and Salzburg. Two animal pieces which he exhibited at the Vienna Exhibition of 1824 were regarded as remarkable productions for his years, and led to his receiving commissions in 1825 and 1826 from Prince Metternich and Caraman, the French ambassador. His reputation was greatly increased by his picture "The Storm," exhibited in 1829, and from that time his works were much sought after and obtained correspondingly high prices. His "Field Labourer" was regarded by many as the most noteworthy picture in the Vienna exhibition of 1834, and his numerous animal pieces have entitled him to a place in the first rank of painters of that class of subjects. The peculiarity of his pictures is the representation of human and animal figures in connexion with appropriate landscapes and in characteristic situations so as to manifest nature as a living whole, and he particularly excels in depicting the free life of animals in wild mountain scenery. Along with great mastery of the technicalities of his art, his works exhibit patient and keen observation, free and correct handling of details, and bold and clear colouring. He died at Vienna on the 7th of July 1862.

Many of his pictures have been engraved, and after his death a selection of fifty-three of his works was prepared for this purpose by the Austrian _Kunstverein_ (Art Union).

GAUGE, or GAGE (Med. Lat. _gauja, jaugia_, Fr. _jauge_, perhaps connected with Fr. _jale_, a bowl, _galon_, gallon), a standard of measurement, and also the name given to various instruments and appliances by which measurement is effected. The word seems to have been primarily used in connexion with the process of ascertaining the contents of wine casks; the name gauger is still applied to certain custom-house officials in the United States, and in Scotland it means an exciseman. Thence it was extended to other measurements, and used of the instruments used in making them or of the standards to which they were referred. In the mechanical arts gauges are employed in great variety to enable the workmen to ascertain whether the object he is making is of the proper dimensions (see TOOL), and similar gauges of various forms are employed to ascertain and to specify the sizes of manufactured articles such as wire and screws. A rain gauge is an apparatus for measuring the amount of the rainfall at any locality, and a wind gauge indicates the pressure and force of the wind. The boilers of steam engines are provided with a water gauge and a steam or pressure gauge. The purpose of the former is to enable the attendant to see whether or not there is a sufficient quantity of water in the boiler. It consists of two cocks or taps communicating with the interior, one being placed at the lowest point to which it is permissible for the water to fall, and the other at the point above which it should not rise; a glass tube connects the two cocks, and when they are both open the water in this stands at the same level as in the boiler. The steam gauge shows the pressure of the steam in the boiler. One of the commonest forms, known as the Bourdon gauge, depends on the fact that a curved tube tends to straighten itself if the pressure within it is greater than that outside it. This gauge therefore consists of a curved or coiled tube of elastic material, and preferably of elliptic section, connected with the boiler and arranged with a multiplying gear so that its bending or unbending actuates a pointer moving over a graduated scale. If the pressure within the tube is less than that outside it, the tube tends to bend or coil itself up further; with a pointer arranged as before, the gauge then becomes a vacuum gauge, indicating how far the pressure in the vessel to which it is attached is below that of the atmosphere. In railway engineering the gauge of a line is the distance between the two rails (see RAILWAY). In nautical language, a ship is said to have the weather gage when she is to windward of another, and similarly the lee gage when to leeward of another; in this sense the word is usually spelt "gage," a spelling which prevails in America for all senses.

GAUHATI, a town of British India, in the Kamrup district of Eastern Bengal and Assam, mainly on the left or south, but partly on the right bank of the Brahmaputra. Pop. (1901) 14,244. It is beautifully situated, with an amphitheatre of wooded hills to the south, but is not very healthy. There are many evidences, such as ancient earthworks and tanks, of its historical importance. During the 17th century it was taken and retaken by Mahommedans and Ahoms eight times in fifty years, but in 1681 it became the residence of the Ahom governor of lower Assam, and in 1786 the capital of the Ahom raja. On the cession of Assam to the British in 1826 it was made the seat of the British administration of Assam, and so continued till 1874, when the headquarters were removed to Shillong in the Khasi hills, 67 m. distant, with which Gauhati is connected by an excellent cart-road. Two much-frequented places of Hindu pilgrimage are situated in the immediate vicinity, the temple of Kamakhya on a hill 2 m. west of the town, and the rocky island of Umananda in the mid-channel of the Brahmaputra. Gauhati is still the headquarters of the district and of the Brahmaputra Valley division, though no longer a military cantonment. It is the river terminus of a section of the Assam-Bengal railway. There are a second-grade college, a government high school, a law class and a training school for masters. Gauhati is an important centre of river trade, and the largest seat of commerce in Assam. Cotton-ginning, flour-milling, and an export trade in mustard seed, cotton, silk and forest produce are carried on. Gauhati suffered very severely from the earthquake of the 12th of June 1897.

GAUL, GILBERT WILLIAM (1855- ), American artist, was born in Jersey City, New Jersey, on the 31st of March 1855. He was a pupil of J.G. Brown and L.E. Wilmarth, and he became a painter of military pictures, portraying incidents of the American Civil War. He was elected an associate of the National Academy of Design in 1880, and in 1882 a full academician, and in the latter year became a member of the Society of American Artists. His important works include: "Charging the Battery," "News from Home," "Cold Comfort on the Outpost," "Silenced," "On the Look-out," and "Guerillas returning from a Raid."

GAUL, the modern form of the Roman _Gallia_, the name of the two chief districts known to the Romans as inhabited by Celtic-speaking peoples, (a) _Gallia Cisalpina_ (or _Citerior_, "Hither"), i.e. north Italy between Alps and Apennines and (b) the far more important _Gallia Transalpina_ (or _Ulterior_, "Further"), usually called _Gallia_ (Gaul) simply, the land bounded by the Alps, the Mediterranean, the Pyrenees, the Atlantic, the Rhine, i.e. modern France and Belgium with parts of Holland, Germany and Switzerland. The Greek form of _Gallia_ was [Greek: Galatia], but Galatia in Latin denoted another Celtic region in central Asia Minor, sometimes styled _Gallograecia_.

(a) Gallia Cisalpina was mainly conquered by Rome by 222 B.C.; later it adopted Roman civilization; about 42 B.C. it was united with Italy and its subsequent history is merged in that of the peninsula. Its chief distinctions are that during the later Republic and earlier Empire it yielded excellent soldiers, and thus much aided the success of Caesar against Pompey and of Octavian against Antony, and that it gave Rome the poet Virgil (by origin a Celt), the historian Livy, the lyrist Catullus, Cornelius Nepos, the elder and the younger Pliny and other distinguished writers.[1]

(b) Gaul proper first enters ancient history when the Greek colony of Massilia was founded (? 600 B.C.). Roman armies began to enter it about 218 B.C. In 121 B.C. the coast from Montpellier to the Pyrenees (i.e. all that was not Massiliot) with its port of Narbo (mod. _Narbonne_) and its trade route by Toulouse to the Atlantic, was formed into the province of Gallia Narbonensis and Narbo itself into a Roman municipality. Commercial motives prompted the step, and Roman traders and land speculators speedily flocked in. Gradually the province was extended north of Massilia, up the Rhone, while the Greek town itself became weak and dependent on Rome.

It is not, however, until the middle of the 1st century B.C. that we have any detailed knowledge of pre-Roman Gaul. The earliest account is that contained in the _Commentaries_ of Julius Caesar. According to this authority, Gaul was at that time divided among three peoples, more or less distinct from one another, the Aquitani, the Gauls, who called themselves Celts, and the Belgae. The first of these extended from the Pyrenees to the Garumna (Garonne); the second, from that river to the Sequana (Seine) and its chief tributary the Matrona (Marne), reaching eastward presumably as far as the Rhenus (Rhine); and the third, from this bounding line to the mouth of the last-named river, thus bordering on the Germans. By implication Caesar recognizes as a fourth division the province of Gallia Narbonensis. By far the greater part of the country was a plain watered by numerous rivers, the chief of which have already been mentioned, with the exception of its great central stream, the Liger or Ligeris (Loire). Its principal mountain ranges were Cebenna or Gebenna (Cévennes) in the south, and Jura, with its continuation Vosegus or Vogesus (Vosges), in the east. The tribes inhabiting Gaul in Caesar's time, and belonging to one or other of the three races distinguished by him, were numerous. Prominent among them, and dwelling in the division occupied by the Celts, were the Helvetii, the Sequani and the Aedui, in the basins of the Rhodanus and its tributary the Arar (Saône), who, he says, were reckoned the three most powerful nations in all Gaul; the Arverni in the mountains of Cebenna; the Senones and Carnutes in the basin of the Liger; the Veneti and other Armorican tribes between the mouths of the Liger and Sequana. The Nervii, Bellovaci, Suessiones, Remi, Morini, Menapii and Aduatuci were Belgic tribes; the Tarbelli and others were Aquitani; while the Allobroges inhabited the north of the Provincia, having been conquered in 121 B.C. The ethnological divisions thus set forth by Caesar have been much discussed (see CELT, and articles on the chief tribes).

The Gallic Wars (58-51) of Caesar (q.v.) added all the rest of Gaul, north-west of the Cévennes, to the Rhine and the Ocean, and in 49 also annexed Massilia. All Gaul was now Roman territory. Now the second period of her history opens; it remained for Roman territory to become romanized.

Caesar had no time to organize his conquest; this work was left to Augustus. As settled by him, and in part perhaps also by his successor Tiberius, it fell into the following five administrative areas.

(i) _Narbonensis_, that is, the land between Alps, sea and Cévennes, extending up the Rhone to Vienne, was as Augustus found it, distinct in many ways from the rest of Gaul. By nature it is a sun-steeped southern region, the home of the vine and olive, of the minstrelsy of the Provençal and the exuberance of Tartarin, distinct from the colder and more sober north. By history it had already (in the time of Augustus) been Roman for from 80 to 100 years and was familiar with Roman ways. It was ready to be Italianized and it was civilized enough to need no garrison. Accordingly, it was henceforward governed by a proconsul (appointed by the senate) and freed from the burden of troops, while its local government was assimilated to that of Italy. The old Celtic tribes were broken up: instead, municipalities of Roman citizens were founded to rule their territories. Thus the Allobroges now disappear and the _colonia_ of Vienna takes their place: the Volcae vanish and we find Nemausus (Nîmes). Thus thrown into Italian fashion, the province took rapidly to Italian ways. By A.D. 70 it was "Italia verius quam provincia" (Pliny). The Gauls obviously had a natural bias towards the Italian civilization, and there soon became no difference between Italy and southern Gaul. But though education spread, the results were somewhat disappointing. Trade flourished; the corporations of bargemen and the like on the Rhone made money; the many towns grew rich and could afford splendid public buildings. But no great writer and no great administrator came from Narbonensis; itinerant lecturers and journalists alone were produced in plenty, and at times minor poets.

(ii.-iv.) Across the Cévennes lay Caesar's conquests, Atlantic in climate, new to Roman ways. The whole area, often collectively styled "Gallia Comata," often "Tres Provinciae," was divided into three provinces, each under a _legatus pro praetore_ appointed by the emperor, with a common capital at Lugudunum (Lyons). The three provinces were: _Aquitania_, reaching from the Pyrenees almost to the Loire; _Lugudunensis_, the land between Loire and Seine, reaching from Brittany in the west to Lyons in the south-east; and _Belgica_ in the north. The boundaries, it will be observed, were wholly artificial. Here also it was found possible to dispense with garrisons, not because the provinces were as peaceful as Narbonensis, but because the Rhine army was close at hand. As befitted an unromanized region, the local government was unlike that of Italy or Narbonensis. Roman municipalities were not indeed unknown, but very few: the local authorities were the magistrates of the old tribal districts. Local autonomy was here carried to an extreme. But the policy succeeded. The Gauls of the Three Provinces, or some of them, revolted in A.D. 21 under Florus and Sacrovir, in 68 under Vindex, and in 70 under Classicus and Tutor (see CIVILIS, CLAUDIUS). But all five leaders were romanized nobles, with Roman names and Roman citizenship, and their risings were directed rather against the Roman government than the Roman empire. In general, the Gauls of these provinces accepted Roman civilization more or less rapidly, and in due course became hardly distinguishable from the Italian. In particular, they eagerly accepted the worship of "Augustus and Rome," devised by the first emperor as a bond of state religion connecting the provinces with Rome. Each August, despite the heat, representatives from the 60 (or 64) tribes of Gallia Comata met at Lyons, elected a priest, "sacerdos ad aram Augusti et Romae," and held games. The post of representative, and still more that of priest, was eagerly coveted and provided a scope for the ambitions which despotism usually crushes. It agrees with the vigorous development of this worship that the Three Provinces, though romanized, retained their own local feeling. Even in the 3rd century the cult of Celtic deities (Hercules Magusanus, Deusoniensis, &c.) were revived, the Celtic _leuga_ reintroduced instead of the Roman mile on official milestones, and a brief effort made to establish an independent, though romanized, Gaul under Postumus and his short-lived successors (A.D. 250-273). Not only was the area too large and strong to lose its individuality: it was also too rural and too far from the Mediterranean to be romanized as fully and quickly as Narbonensis. It is even probable that Celtic was spoken in forest districts into the 4th century A.D. Town life, however, grew. The _chefs-lieux_ of the tribes became practically, though not officially, municipalities, and many of these towns reached considerable size and magnificence of public buildings. But they attest their tribal relations by their appellations, which are commonly drawn from the name of the tribe and not of the town itself. Thus the capitals of the Remi and Parisii were actually Durocortorum and Lutetia: the appellations in use were Remis or Remus, Parisiis or Parisius--these forms being indeclinable nouns formed from a sort of locative of the tribe names. Literature also flourished. In the latest empire Ausonius, Symmachus, Apollinaris, Sidonius and other Gaulish writers, chiefly of Gallia Comata, kept alive the classical literary tradition, not only for Gaul but for the world.

(v.) The fifth division of Gaul was the Rhenish military frontier. Augustus had planned the conquest of Germany up to the Elbe. His plans were foiled by the courage of Arminius and the inability of the Roman exchequer to pay a larger army. Instead, his successor Tiberius organized the Rhine frontier in two military districts. The northern one was the valley of the Meuse and that of the Rhine to a point just south of Bonn: the southern was the rest of the Rhine valley to Switzerland. Each district was garrisoned at first by four, later by fewer legions, which were disposed at various times in some of the following fortresses: Vetera (Xanten), Novaesium (Neuss), Bonne (Bonn), Moguntiacum (Mainz), Argentorate (Strassburg) and Vindonissa (Windisch in Switzerland). At first the districts were purely military, were called, after the garrisons, "exercitus Germanicus superior" (south) and "inferior" (north). Later one or two municipalities were founded--Colonia Agrippinensis at Cologne (A.D. 51), Colonia Augusta Treverorum at Trier (date uncertain), Colonia Ulpia Traiana outside Vetera--and about 80-90 A.D. the two "Exercitus" were turned into the two provinces of Upper and Lower Germany. The armies in these districts formed the defence of Gaul against German invaders. They also helped to keep Gaul itself in order and their presence explains why the four provinces of Gaul proper contained no troops.

These provincial divisions were modified by Diocletian but without seriously affecting the life of Gaul. The whole country, indeed, continued Roman and fairly safe from barbarian invasions till after 400. In 407 a multitude of Franks, Vandals, &c., burst over Gaul: Roman rule practically ceased and the three kingdoms of the Visigoths, Burgundians and Franks began to form. There were still a Roman general and Roman troops when Attila was defeated in the _campi Catalaunici_ in A.D. 451, but the general, Aetius, was "the last of the Romans," and in 486 Clovis the Frank ended the last vestige of Roman rule in Gaul.

For Roman antiquities in Gaul see, beside articles on the modern towns (ARLES, NÎMES, ORANGE &c.), BIBRACTE, ALESIA, ITIUS PORTUS, AQUEDUCT, ARCHITECTURE, AMPHITHEATRE, &c.; for religion see DRUIDISM; for the famous schools of Autun, Lyons, Toulouse, Nîmes, Vienne, Marseilles and Narbonne, see J.E. Sandys, _History of Classical Scholarship_ (ed. 1906-1908), i. pp. 247-250; for the Roman provinces, Th. Mommsen, _Provinces of the Roman Empire_ (trans. 1886), vol. i. chap. iii. See also Desjardins, _Géographie historique et administrative de la Gaule romaine_ (Paris, 1877); Fustel de Coulanges, _Histoire des institutions politiques de l'ancienne France_ (Paris, 1877); for Caesar's campaigns, article CAESAR, JULIUS, and works quoted; for coins, art. NUMISMATICS and articles in the _Numismatische Zeitschrift_ and _Revue numismatique_ (e.g. Blanchet, 1907, pp. 461 foll.). (F. J. H.)

FOOTNOTE:

[1] When Cisalpine Gaul became completely Romanized, it was often known as "Gallia Togata," while the Province was distinguished as "Gallia Bracata" (_bracae_, incorrectly _braccae_, "trousers"), from the long trousers worn by the inhabitants, and the rest of Gaul as "Gallia Comata," from the inhabitants wearing their hair long.

GAULT, in geology, one of the members of the Lower Cretaceous System. The name is still employed provincially in parts of England for a stiff blue clay of any kind; by the earlier writers it was sometimes spelt "Galt" or "Golt."

The formation now known as Gault in England has been variously designated "Blue Marle," "Brick Earth," "Golt Brick Earth" and "Oak-tree-soil." In certain parts of the south of England the Gault appears as a well-marked deposit of clay, lying between two sandy formations; the one above came to be known as the "Upper Greensand," the one below being the "Lower Greensand" (see GREENSAND). Since the typical clayey Gault is continually taking on a sandy facies as it is traced both horizontally and vertically; and since the fossils of the Upper Greensand and Gault are inseparably related, it has been proposed by A.J. Jukes-Browne that these two series of beds should be regarded as the arenaceous and argillaceous phases of a single formation, to which he has given the name "Selbornian" (from the village of Selborne where the beds are well developed). Lithologically, then, the Selbornian includes the blue and grey clays and marls of the Gault proper; the glauconitic sands of the Upper Greensand, and their local equivalent, the "malm," "malm rock" or "firestone," which in places passes into the micaceous sandstone containing sponge spicules and globules of silica, the counterpart of the rock called "gaize" on the same horizon in northern France. In Yorkshire, Lincolnshire and parts of Norfolk the Selbornian is represented by the Red Chalk. The malm is a ferruginous siliceous rock, the silica being mainly in the colloidal condition in the form of globules and sponge spicules; some quartz grains, mica and glauconite are usually present along with from 2 to 25% of calcareous matter. Chert-bands and nodules are common in the Upper Greensand of certain districts; and calcareous concretions, locally recognized as cowstones (Lyme Regis), doggers or buhrstones, are not infrequent.

The principal divisions of the Selbornian stage with their characteristic zonal fossils are as follows:--

Warminster Beds _Pecten asper_ and _Cardiaster fossarius_.

Upper Gault Devizes Beds or Merstham Beds with _Schloenbachia rostralus_.

/ _Hoplites lautus._ Lower Gault < _H. interruptus._ \ _Acanthoceras mammillatum._

The Gault (with Upper Greensand) crops out all round the Wealden area; it extends beneath the London basin and reappears from beneath the northern scarp of the Chalk along the foot of the Chiltern Hills to near Tring. In the south of England the Gault clay is fairly constant in the lower part, with the Greensand above; the clay, however, passes into sand as it is followed westward and, as already pointed out, the clay and sand appear to pass into a red chalk towards the north-east. The Gault overlaps the Lower Greensand towards the east, where it rests upon the old Paleozoic axis; it also overlaps the same formation towards the west about Frome, and thence passes unconformably across the Portlandian beds, Kimeridge Clay, Corallian beds and Oxford Clay; in south Dorsetshire it rests upon the Wealden Series. The Gault (with Upper Greensand) passes on to the Jurassic and Rhaetic rocks near Axmouth, and oversteps farther westward, in the Haldon Hills, on to the Permian. A large outlier occurs on the Blackdown Hills of Devonshire. Good localities for fossils are Folkestone--where many of the shells are preserved with their original pearly nacre,--Burnham, Merstham, Isle of Wight, the Blackdown and Haldon Hills, Warminster, Hunstanton and Speeton, Black Venn near Lyme Regis, and Devizes (malmstone and gaize). The beds are well developed in the vale of Wardour, and in the Isle of Wight; the Gault forms the so-called "blue slipper" at Ventnor which has been the cause of the landslip or undercliff.

The Gault of north France is very similar to that in the south of England, but the French term _Albien_ includes only a portion of the Selbornian formation. The Gault of north-west Germany embraces beds that would be classed as _Albien_ and _Aptien_ by French authors; it comprises the "Flammenmergel"--a pale siliceous marl shot with flame-shaped darker patches--a clay with _Belemnites minimus_, and the "Gargasmergel" (Aptian). In the Diester and Teutoberger Wald, and in the region of Halberstadt, the clays and marls are replaced by sandstones, the so-called _Gault-Quader_. Continental writers usually place the Gault or Albian at the summit of the Lower Cretaceous; while with English geologists the practice is to commence the Upper Cretaceous with this formation. In addition to the fossils already noticed, the following may be mentioned: _Acanthoceras Desmoceras Beaudanti, Hoplites splendens, Hamites, Scaphites, Turrilites, Aporrhais retusa, Trigonia aliforme_, also _Ichthyosaurus_ and _Ornithocheirus_ (Pterodactyl). From the clays, bricks and tiles are made at Burham, Barnwell, Dunton Green, Arlesey, Hitchin, &c. The cherts in the Greensand portion are used for road metal, and in the Blackdown Hills, for scythe stones; hearthstone is obtained about Merstham; phosphatic nodules occur at several horizons.

See CRETACEOUS SYSTEM; ALBIAN; APTIAN; also A.J. Jukes-Browne, "The Gault and Upper Greensand of England." vol. i., _Cretaceous Rocks of Britain_; _Mem. Geol. Survey_, 1900.

GAUNTLET (a diminutive of the Fr. _gant_, glove), a large form of glove, and especially the steel-plated glove of medieval armour. To "run the gauntlet," i.e. to run between two rows of men who, armed with sticks, rope-ends or other weapons, beat and strike at the person so running, was formerly a punishment for military and naval offences. It was abolished in the Prussian army by Scharnhorst. As a method of torturing prisoners, it was employed among the North American Indians. "Gauntlet" (earlier "gantlet") in this expression is a corruption of "gantlope," from a Swedish _gatlope_, from _gata_, lane, and _lopp_, a course (cf. Ger. _gassenlaufen_, to run the gauntlet). According to the _New English Dictionary_ the word became familiar in England at the time of the Thirty Years' War.

GAUR, or LAKHNAUTI, a ruined city of British India, in Malda district of Eastern Bengal and Assam. The ruins are situated about 8 m. to the south of English Bazar, the civil station of the district of Malda, and on the eastern bank of the Bhagirathi, an old channel of the Ganges. It is said to have been founded by Lakshman, and its most ancient name was Lakshmanavati, corrupted into Lakhnauti. Its known history begins with its conquest in A.D. 1198 by the Mahommedans, who retained it as the chief seat of their power in Bengal for more than three centuries. When the Afghan kings of Bengal established their independence, they transferred their seat of government (about 1350) to Pandua (q.v.), also in Malda district, and to build their new capital they plundered Gaur of every monument that could be removed. When Pandua was in its turn deserted (A.D. 1453), Gaur once more became the capital under the name of Jannatabad; it remained so as long as the Mahommedan kings retained their independence. In A.D. 1564 Sulaiman Kirani, a Pathan adventurer, abandoned it for Tanda, a place somewhat nearer the Ganges. Gaur was sacked by Sher Shah in 1539, and was occupied by Akbar's general in 1575, when Daud Shah, the last of the Afghan dynasty, refused to pay homage to the Mogul emperor. This occupation was followed by an outbreak of the plague, which completed the downfall of the city, and since then it has been little better than a heap of ruins, almost overgrown with jungle.

The city in its prime measured 7½ m. from north to south, with a breadth of 1 to 2 m. With suburbs it covered an area of 20 to 30 sq. m., and in the 16th century the Portuguese historian Faria y Sousa described it as containing 1,200,000 inhabitants. The ramparts of this walled city, which was surrounded by extensive suburbs, still exist; they were works of vast labour, and were on the average about 40 ft. high, and 180 to 200 ft. thick at the base. The facing of masonry and the buildings with which they were covered have now disappeared, and the embankments themselves are overgrown with dense jungle. The western side of the city was washed by the Ganges, and within the space enclosed by these embankments and the river stood the city of Gaur proper, with the fort containing the palace in its south-west corner. Radiating north, south and east from the city, other embankments are to be traced running through the suburbs and extending in certain directions for 30 or 40 m. Surrounding the palace is an inner embankment of similar construction to that which surrounds the city, and even more overgrown with jungle. A deep moat protects it on the outside. To the north of the outer enbankment lies the Sagar Dighi, a great reservoir, 1600 yds. by 800 yds., dating from A.D. 1126.

Fergusson in his _History of Eastern Architecture_ thus describes the general architectural style of Gaur:--"It is neither like that of Delhi nor Jaunpore, nor any other style, but one purely local and not without considerable merit in itself; its principal characteristic being heavy short pillars of stone supporting pointed arches and vaults in brick--whereas at Jaunpore, for instance, light pillars carried horizontal architraves and flat ceilings." Owing to the lightness of the small, thin bricks, which were chiefly used in the making of Gaur, its buildings have not well withstood the ravages of time and the weather; while much of its enamelled work has been removed for the ornamentation of the surrounding cities of more modern origin. Moreover, the ruins long served as a quarry for the builders of neighbouring towns and villages, till in 1900 steps were taken for their preservation by the government. The finest ruin in Gaur is that of the Great Golden Mosque, also called Bara Darwaza, or twelve-doored (1526). An arched corridor running along the whole front of the original building is the principal portion now standing. There are eleven arches on either side of the corridor and one at each end of it, from which the mosque probably obtained its name. These arches are surmounted by eleven domes in fair preservation; the mosque had originally thirty-three.

The Small Golden or Eunuch's mosque, in the ancient suburb of Firozpur, has fine carving, and is faced with stone fairly well preserved. The Tantipara mosque (1475-1480) has beautiful moulding in brick, and the Lotan mosque of the same period is unique in retaining its glazed tiles. The citadel, of the Mahommedan period, was strongly fortified with a rampart and entered through a magnificent gateway called the Dakhil Darwaza (?1459-1474). At the south-east corner was a palace, surrounded by a wall of brick 66 ft. high, of which a part is standing. Near by were the royal tombs. Within the citadel is the Kadam Rasul mosque (1530), which is still used, and close outside is a tall tower called the Firoz Minar (perhaps signifying "tower of victory"). There are a number of Mahommedan buildings on the banks of the Sagar Dighi, including, notably, the tomb of the saint Makhdum Shaikh Akhi Siraj (d. 1357), and in the neighbourhood is a burning ghat, traditionally the only one allowed to the use of the Hindus by their Mahommedan conquerors, and still greatly venerated and frequented by them. Many inscriptions of historical importance have been found in the ruins.

See M. Martin (Buchanan Hamilton), _Eastern India_, vol. iii. (1831); G.H. Ravenshaw, _Gaur_ (1878); James Fergusson, _History of Indian and Eastern Architecture_ (1876); _Reports of the Archaeological Surveyor, Bengal Circle_ (1900-1904).

GAUR, the native name of the wild ox, _Bos (Bibos) gaurus_, of India, miscalled bison by sportsmen. The gaur, which extends into Burma and the Malay Peninsula, where it is known as seladang, is the typical representative of an Indo-Malay group of wild cattle characterized by the presence of a ridge on the withers, the compressed horns, and the white legs. The gaur, which reaches a height of nearly 6 ft. at the shoulder, is specially characterized by the forward curve and great elevation of the ridge between the horns. The general colour is blackish-grey. Hill-forests are the resort of this species.

GAUSS, KARL FRIEDRICH (1777-1855), German mathematician, was born of humble parents at Brunswick on the 30th of April 1777, and was indebted for a liberal education to the notice which his talents procured him from the reigning duke. His name became widely known by the publication, in his twenty-fifth year (1801), of the _Disquisitiones arithmeticae_. In 1807 he was appointed director of the Göttingen observatory, an office which he retained to his death: it is said that he never slept away from under the roof of his observatory, except on one occasion, when he accepted an invitation from Baron von Humboldt to attend a meeting of natural philosophers at Berlin. In 1809 he published at Hamburg his _Theoria motus corporum coelestium_, a work which gave a powerful impulse to the true methods of astronomical observation; and his astronomical workings, observations, calculations of orbits of planets and comets, &c., are very numerous and valuable. He continued his labours in the theory of numbers and other analytical subjects, and communicated a long series of memoirs to the Royal Society of Sciences (_Königliche Gesellschaft der Wissenschaften_) at Göttingen. His first memoir on the theory of magnetism, _Intensitas vis magneticae terrestris ad mensuram absolutam revocata_, was published in 1833, and he shortly afterwards proceeded, in conjunction with Wilhelm Weber, to invent new apparatus for observing the earth's magnetism and its changes; the instruments devised by them were the declination instrument and the bifilar magnetometer. With Weber's assistance he erected in 1833 at Göttingen a magnetic observatory free from iron (as Humboldt and F.J.D. Arago had previously done on a smaller scale), where he made magnetic observations, and from this same observatory he sent telegraphic signals to the neighbouring town, thus showing the practicability of an electromagnetic telegraph. He further instituted an association (_Magnetischer Verein_), composed at first almost entirely of Germans, whose continuous observations on fixed term-days extended from Holland to Sicily. The volumes of their publication, _Resultate am den Beobachtungen des magnetischen Vereins_, extend from 1836 to 1839; and in those for 1838 and 1839 are contained the two important memoirs by Gauss, _Allgemeine Theorie des Erdmagnetismus, and the Allgemeine Lehrsätze_--on the theory of forces attracting according to the inverse square of the distance. The instruments and methods thus due to him are substantially those employed in the magnetic observatories throughout the world. He co-operated in the Danish and Hanoverian measurements of an arc and trigonometrical operations (1821-1848), and wrote (1843, 1846) the two memoirs _Über Gegenstände der höheren Geodäsie_. Connected with observations in general we have (1812-1826) the memoir _Theoria combinationis observationum erroribus minimis obnoxia_, with a second part and a supplement. Another memoir of applied mathematics is the _Dioptrische Untersuchungen_ (1840). Gauss was well versed in general literature and the chief languages of modern Europe, and was a member of nearly all the leading scientific societies in Europe. He died at Göttingen on the 23rd of February 1855. The centenary of his birth was celebrated (1877) at his native place, Brunswick.

Gauss's collected works were published by the Royal Society of Göttingen, in 7 vols. 4to (Gött., 1863-1871), edited by E.J. Schering--(1) the _Disquisitiones arithmeticae_, (2) _Theory of Numbers_, (3) _Analysis_, (4) _Geometry and Method of Least Squares_, (5) _Mathematical Physics_, (6) _Astronomy_, and (7) the _Theoria motus corporum coelestium_. Additional volumes have since been published, _Fundamente der Geometrie usw_. (1900), and _Geodatische Nachträge zu Band iv_. (1903). They include, besides his various works and memoirs, notices by him of many of these, and of works of other authors in the _Göttingen gelehrte Anzeigen_, and a considerable amount of previously unpublished matter, _Nachlass_. Of the memoirs in pure mathematics, comprised for the most part in vols, ii., iii. and iv. (but to these must be added those on _Attractions_ in vol. v.), it may be safely said there is not one which has not signally contributed to the progress of the branch of mathematics to which it belongs, or which would not require to be carefully analysed in a history of the subject. Running through these volumes in order, we have in the second the memoir, _Summatio quarundam serierum singularium_, the memoirs on the theory of biquadratic residues, in which the notion of complex numbers of the form a + _bi_ was first introduced into the theory of numbers; and included in the _Nachlass_ are some valuable tables. That for the conversion of a fraction into decimals (giving the complete period for all the prime numbers up to 997) is a specimen of the extraordinary love which Gauss had for long arithmetical calculations; and the amount of work gone through in the construction of the table of the number of the classes of binary quadratic forms must also have been tremendous. In vol. iii. we have memoirs relating to the proof of the theorem that every numerical equation has a real or imaginary root, the memoir on the _Hypergeometric Series_, that on _Interpolation_, and the memoir _Determinatio attractionis_--in which a planetary mass is considered as distributed over its orbit according to the time in which each portion of the orbit is described, and the question (having an implied reference to the theory of secular perturbations) is to find the attraction of such a ring. In the solution the value of an elliptic function is found by means of the _arithmetico-geometrical mean_. The _Nachlass_ contains further researches on this subject, and also researches (unfortunately very fragmentary) on the lemniscate-function, &., showing that Gauss was, even before 1800, in possession of many of the discoveries which have made the names of N.H. Abel and K.G.J. Jacobi illustrious. In vol. iv. we have the memoir _Allgemeine Auflösung_, on the graphical representation of one surface upon another, and the _Disquisitiones generales circa superficies curvas_. (An account of the treatment of surfaces which he originated in this paper will be found in the article SURFACE.) And in vol. v. we have a memoir _On the Attraction of Homogeneous Ellipsoids_, and the already mentioned memoir _Allgemeine Lehrsätze_, on the theory of forces attracting according to the inverse square of the distance. (A. Ca.)

GAUSSEN, FRANÇOIS SAMUEL ROBERT LOUIS (1790-1863), Swiss Protestant divine, was born at Geneva on the 25th of August 1790. His father, Georg Markus Gaussen, a member of the council of two hundred, was descended from an old Languedoc family which had been scattered at the time of the religious persecutions in France. At the close of his university career at Geneva, Louis was in 1816 appointed pastor of the Swiss Reformed Church at Satigny near Geneva, where he formed intimate relations with J.E. Cellérier, who had preceded him in the pastorate, and also with the members of the dissenting congregation at Bourg-de-Four, which, together with the Église du témoignage, had been formed under the influence of the preaching of James and Robert Haldane in 1817. The Swiss revival was distasteful to the pastors of Geneva (_Vénérable Compagnie des Pasteurs_), and on the 7th of May 1817 they passed an ordinance hostile to it. As a protest against this ordinance, in 1819 Gaussen published in conjunction with Cellérier a French translation of the Second Helvetic Confession, with a preface expounding the views he had reached upon the nature, use and necessity of confessions of faith; and in 1830, for having discarded the official catechism of his church as being insufficiently explicit on the divinity of Christ, original sin and the doctrines of grace, he was censured and suspended by his ecclesiastical superiors. In the following year he took part in the formation of a _Société Évangélique_ (_Evangelische Gesellschaft_). When this society contemplated, among other objects, the establishment of a new theological college, he was finally deprived of his charge. After some time devoted to travel in Italy and England, he returned to Geneva and ministered to an independent congregation until 1834, when he joined Merle d'Aubigné as professor of systematic theology in the college which he had helped to found. This post he continued to occupy until 1857, when he retired from the active duties of the chair. He died at Les Grottes, Geneva, on the 18th of June 1863.

His best-known work, entitled _La Théopneustie ou pleine inspiration des saintes écritures_, an elaborate defence of the doctrine of "plenary inspiration," was originally published in Paris in 1840, and rapidly gained a wide popularity in France, as also, through translations, in England and America. It was followed in 1860 by a supplementary treatise on the canon (_Le Canon des saintes écritures au double point de vue de la science et de la foi_), which, though also popular, has hardly been so widely read.

See the article in Herzog-Hauck, _Realencyklopädie_ (1899).

GAUTIER, ÉMILE THÉODORE LÉON (1832-1897), French literary historian, was born at Hâvre on the 8th of August 1832. He was educated at the École des Chartes, and became successively keeper of the archives of the department of Haute-Marne and of the imperial archives at Paris under the empire. In 1871 he became professor of palaeography at the École des Chartes. He was elected member of the Academy of Inscriptions in 1887, and became chief of the historical section of the national archives in 1893. Léon Gautier rendered great services to the study of early French literature, the most important of his numerous works on medieval subjects being a critical text (Tours, 1872) with translation and introduction of the _Chanson de Roland_, and _Les Épopées françaises_ (3 vols., 1866-1867; 2nd ed., 5 vols., 1878-1897, including a _Bibliographie des chansons de geste_). He died in Paris on the 25th of August 1897.

GAUTIER, THÉOPHILE (1811-1872), French poet and miscellaneous writer, was born at Tarbes on the 31st of August 1811. He was educated at the grammar school of that town, and afterwards at the Collège Charlemagne in Paris, but was almost as much in the studios. He very early devoted himself to the study of the older French literature, especially that of the 16th and the early part of the 17th century. This study qualified him well to take part in the Romantic movement, and enabled him to astonish Sainte-Beuve by the phraseology and style of some literary essays which, when barely eighteen years old, he put into the critic's hands. In consequence of this introduction he at once came under the influence of the great Romantic _cénacle_, to which, as to Victor Hugo in particular, he was also introduced by his gifted but ill-starred schoolmate Gérard de Nerval. With Gérard, Petrus Borel, Corot, and many other less known painters and poets whose personalities he has delightfully sketched in the articles collected under the titles of _Histoire du Romantisme_, &c., he formed a minor romantic clique who were distinguished for a time by the most extravagant eccentricity. A flaming crimson waistcoat and a great mass of waving hair were the outward signs which qualified Gautier for a chief rank among the enthusiastic devotees who attended the rehearsals of _Hernani_ with red tickets marked "Hierro," performed mocking dances round the bust of Racine, and were at all times ready to exchange word or blow with the _perruques_ and _grisâtres_ of the classical party. In Gautier's case these freaks were not inconsistent with real genius and real devotion to sound ideals of literature. He began (like Thackeray, to whom he presents in other ways some striking points of resemblance) as an artist, but soon found that his true powers lay in another direction.

His first considerable poem, _Albertus_ (1830), displayed a good deal of the extravagant character which accompanied rather than marked the movement, but also gave evidence of uncommon command both of language and imagery, and in particular of a descriptive power hardly to be excelled. The promise thus given was more than fulfilled in his subsequent poetry, which, in consequence of its small bulk, may well be noticed at once and by anticipation. The _Comédie de la mort_, which appeared soon after (1832), is one of the most remarkable of French poems, and though never widely read has received the suffrage of every competent reader. Minor poems of various dates, published in 1840, display an almost unequalled command over poetical form, an advance even over _Albertus_ in vigour, wealth and appropriateness of diction, and abundance of the special poetical essence. All these good gifts reached their climax in the _Émaux et camées_, first published in 1856, and again, with additions, just before the poet's death in 1872. These poems are in their own way such as cannot be surpassed. Gautier's poetical work contains in little an expression of his literary peculiarities. There are, in addition to the peculiarities of style and diction already noticed, an extraordinary feeling and affection for beauty in art and nature, and a strange indifference to anything beyond this range, which has doubtless injured the popularity of his work.

But it was not, after all, as a poet that Gautier was to achieve either profit or fame. For the theatre, he had but little gift, and his dramatic efforts (if we except certain masques or ballets in which his exuberant and graceful fancy came into play) are by far his weakest. It was otherwise with his prose fiction. His first novel of any size, and in many respects his most remarkable work, was _Mademoiselle de Maupin_ (1835). Unfortunately this book, while it establishes his literary reputation on an imperishable basis, was unfitted by its subject, and in parts by its treatment, for general perusal, and created, even in France, a prejudice against its author which he was very far from really deserving. During the years from 1833 onwards, his fertility in novels and tales was very great. _Les Jeunes-France_ (1833), which may rank as a sort of prose _Albertus_ in some ways, displays the follies of the youthful Romantics in a vein of humorous and at the same time half-pathetic satire. _Fortunio_ (1838) perhaps belongs to the same class. _Jettatura_, written somewhat later, is less extravagant and more pathetic. A crowd of minor tales display the highest literary qualities, and rank with Mérimée's at the head of all contemporary works of the class. First of all must be mentioned the ghost-story of _La Morte amoureuse_, a gem of the most perfect workmanship. For many years Gautier continued to write novels. _La Belle Jenny_ (1864) is a not very successful attempt to draw on his English experience, but the earlier _Militona_ (1847) is a most charming picture of Spanish life. In _Spirite_ (1866) he endeavoured to enlist the fancy of the day for supernatural manifestations, and a _Roman de la momie_ (1856) is a learned study of ancient Egyptian ways. His most remarkable effort in this kind, towards the end of his life, was _Le Capitaine Fracasse_ (1863), a novel, partly of the picaresque school, partly of that which Dumas was to make popular, projected nearly thirty years earlier, and before Dumas himself had taken to the style. This book contains some of the finest instances of his literary power.

Yet neither in poems nor in novels did the main occupation of Gautier as a literary man consist. He was early drawn to the more lucrative task of feuilleton-writing, and for more than thirty years he was among the most expert and successful practitioners of this art. Soon after the publication of _Mademoiselle de Maupin_, in which he had not been too polite to journalism, he became irrevocably a journalist. He was actually the editor of _L'Artiste_ for a time: but his chief newspaper connexions were with _La Presse_ from 1836 to 1854 and with the _Moniteur_ later. His work was mainly theatrical and art criticism. The rest of his life was spent either at Paris or in travels of considerable extent to Spain, the Netherlands, Italy, Turkey, England, Algeria and Russia, all undertaken with a more or less definite purpose of book-making. Having absolutely no political opinions, he had no difficulty in accepting the Second Empire, and received from it considerable favours, in return for which, however, he in no way prostituted his pen, but remained a literary man pure and simple. He died on the 23rd of December 1872.

Accounts of his travels, criticisms of the theatrical and literary works of the day, obituary notices of his contemporaries and, above all, art criticism occupied him in turn. It has sometimes been deplored that this engagement in journalism should have diverted Gautier from the performance of more capital work in literature. Perhaps, however, this regret springs from a certain misconception. Gautier's power was literary power pure and simple, and it is as evident in his slightest sketches and criticisms as in _Émaux et camées or La Morte amoureuse_. On the other hand, his weakness, if he had a weakness, lay in his almost total indifference to the matters which usually supply subjects for art and therefore for literature. He has thus been accused of "lack of ideas" by those who have not cleared their own minds of cant; and in the recent set-back of the critical current against form and in favour of "philosophic" treatment, comment upon him has sometimes been unfavourable. But this injustice will, beyond all question, be redressed again. He was neither immoral, irreligious nor unduly subservient to despotism, but morals, religion and politics (to which we may add science and material progress) were matters of no interest to him. He was to all intents a humanist, as the word was understood in the 15th century. But he was a humorist as well, and this combination, joined to his singularly kindly and genial nature, saved him from some dangers and depravations as well as some absurdities to which the humanist temper is exposed. As time goes on it may be predicted that, though Gautier may not be widely read, yet his writings will never cease to be full of indescribable charm and of very definite instruction to men of letters. Besides those of his works which have been already cited, we may notice _Une Larme du diable_ (1839), a charming mixture of humour and tenderness; _Les Grotesques_ (1844), a volume of early criticisms on some oddities of 17th-century literature; _Caprices et zigzags_ (1845), miscellanies dealing in part with English life; _Voyage en Espagne_ (1845), _Constantinople_ (1854), _Voyage en Russie_ (1866), brilliant volumes of travel; _Ménagerie intime_ (1869) and _Tableaux de siège_ (1872), his two latest works, which display his incomparable style in its quietest but not least happy form.

There is no complete edition of Gautier's works, and the vicomte Spoelberch de Lovenjoul's _Histoire des oeuvres de Théophile Gautier_ (1887) shows how formidable such an undertaking would be. But since his death numerous further collections of articles have been made: _Fusains et eaux-fortes_ and _Tableaux à la plume_ (1880); _L'Orient_ (2 vols., 1881); _Les Vacances du lundi_ (new ed., 1888); _La Nature chez elle_ (new ed., 1891). In 1879 his son-in-law, E. Bergerat, who had married his younger daughter Estelle (the elder, Mme Judith Gautier--herself a writer of distinction--was at one time Mme Catulle Mendès), issued a biography, _Théophile Gautier_, which has been often reprinted. With it should be compared Maxime du Camp's volume in the _Grands Écrivains français_ (1890) and the numerous references in the _Journal des Goncourt_. Critical eulogies, from Sainte-Beuve (repeatedly in the _Causeries_) and Baudelaire (two articles in _L'Art romantique_) downwards, are numerous. The chief of the decriers is Émile Faguet in his _Études littéraires sur le XIX^e siècle_. In 1902 and 1903 there appeared two respectable academic _éloges_ by H. Menai and H. Potez. (G. Sa.)

GAUTIER D'ARRAS, French _trouvère_, flourished in the second half of the 12th century. Nothing is known of his biography except what may be gleaned from his works. He dedicated his romance of _Éracle_ to Theobald V., count of Blois (d. 1191); among his other patrons were Marie, countess of Champagne, daughter of Louis VII. and Eleanor of Guienne and Baldwin IV., count of Hainaut. _Éracle_, the hero of which becomes emperor of Constantinople as Heraclius, is purely a _roman d'aventures_ and enjoyed great popularity. His second romance, _Ille et Galeron_, dedicated to Beatrix, the second wife of Frederick Barbarossa, treats of a similar situation to that outlined in the lay of "_Eliduc_" by Marie de France.

See the _Oeuvres de Gautier d'Arras_, ed. E. Löseth (2 vols., Paris, 1890); _Hist. litt. de la France_, vol. xxii. (1852); A. Dinaux, _Les Trouvères_ (1833-1843), vol. iii.

GAUZE, a light, transparent fabric, originally of silk, and now sometimes made of linen or cotton, woven in an open manner with very fine yarn. It is said to have been originally made at Gaza in Palestine, whence the name. Some of the gauzes from eastern Asia were brocaded with flowers of gold or silver. In the weaving of gauze the warp threads, in addition to being crossed as in plain weaving, are twisted in pairs from left to right and from right to left alternately, after each shot of weft, thereby keeping the weft threads at equal distances apart, and retaining them in their parallel position. The textures are woven either plain, striped or figured; and the material receives many designations, according to its appearance and the purposes to which it is devoted. A thin cotton fabric, woven in the same way, is known as leno, to distinguish it from muslin made by plain weaving. Silk gauze was a prominent and extensive industry in the west of Scotland during the second half of the 18th century, but on the introduction of cotton-weaving it greatly declined. In addition to its use for dress purposes silk gauze is much employed for bolting or sifting flour and other finely ground substances. The term gauze is applied generally to transparent fabrics of whatever fibre made, and to the fine-woven wire-cloth used in safety-lamps, sieves, window-blinds, &c.

GAVARNI, the name by which SULPICE GUILLAUME CHEVALIER (1801-1866), French caricaturist, is known. He is said to have taken the _nom de plume_ from the place where he made his first published sketch. He was born in Paris of poor parents, and started in life as a workman in an engine-building factory. At the same time he attended the free school of drawing. In his first attempts to turn his abilities to some account he met with many disappointments, but was at last entrusted with the drawing of some illustrations for a journal of fashion. Gavarni was then thirty-four years of age. His sharp and witty pencil gave to these generally commonplace and unartistic figures a life-likeness and an expression which soon won for him a name in fashionable circles. Gradually he gave greater attention to this more congenial work, and finally ceased working as an engineer to become the director of the journal _Les Gens du monde_. His ambition rising in proportion to his success, Gavarni from this time followed the real bent of his inclination, and began a series of lithographed sketches, in which he portrayed the most striking characteristics, foibles and vices of the various classes of French society. The letterpress explanations attached to his drawings were always short, but were forcible and highly humorous, if sometimes trivial, and were admirably adapted to the particular subjects. The different stages through which Gavarni's talent passed, always elevating and refining itself, are well worth being noted. At first he confined himself to the study of Parisian manners, more especially those of the Parisian youth. To this vein belong _Les Lorettes_, _Les Actrices_, _Les Coulisses_, _Les Fashionables_, _Les Gentilshommes bourgeois_, _Les Artistes_, _Les Débardeurs_, _Clichy_, _Les Étudiants de Paris_, _Les Baliverneries parisiennes_, _Les Plaisirs champêtres_, _Les Bals masqués_, _Le Carnaval_, _Les Souvenirs du carnaval_, _Les Souvenirs du bal Chicard_, _La Vie des jeunes hommes_, _Les Patois de Paris_. He had now ceased to be director of _Les Gens du monde_; but he was engaged as ordinary caricaturist of _Le Charivari_, and, whilst making the fortune of the paper, he made his own. His name was exceedingly popular, and his illustrations for books were eagerly sought for by publishers. _Le Juif errant_, by Eugène Sue (1843, 4 vols. 8vo), the French translation of Hoffman's tales (1843, 8vo), the first collective edition of Balzac's works (Paris, Houssiaux, 1850, 20 vols. 8vo), _Le Diable à Paris_ (1844-1846, 2 vols. 4to), _Les Français peints par eux-mêmes_ (1840-1843, 9 vols. 8vo), the collection of _Physiologies_ published by Aubert in 38 vols. 18mo (1840-1842),--all owed a great part of their success at the time, and are still sought for, on account of the clever and telling sketches contributed by Gavarni. A single frontispiece or vignette was sometimes enough to secure the sale of a new book. Always desiring to enlarge the field of his observations, Gavarni soon abandoned his once favourite topics. He no longer limited himself to such types as the _lorette_ and the Parisian student, or to the description of the noisy and popular pleasures of the capital, but turned his mirror to the grotesque sides of family life and of humanity at large. _Les Enfants terribles_, _Les Parents terribles_, _Les Fourberies des femmes_, _La Politique des femmes_, _Les Maris vengés_, _Les Nuances du sentiment_, _Les Rêves_, _Les Petits Jeux de société_, _Les Petits Malheurs du bonheur_, _Les Impressions de menage_, _Les Interjections_, _Les Traductions en langue vulgaire_, _Les Propos de Thomas Vireloque_, &c., were composed at this time, and are his most elevated productions. But whilst showing the same power of irony as his former works, enhanced by a deeper insight into human nature, they generally bear the stamp of a bitter and even sometimes gloomy philosophy. This tendency was still more strengthened by a visit to England in 1849. He returned from London deeply impressed with the scenes of misery and degradation which he had observed among the lower classes of that city. In the midst of the cheerful atmosphere of Paris he had been struck chiefly by the ridiculous aspects of vulgarity and vice, and he had laughed at them. But the debasement of human nature which he saw in London appears to have affected him so forcibly that from that time the cheerful caricaturist never laughed or made others laugh again. What he had witnessed there became the almost exclusive subject of his drawings, as powerful, as impressive as ever, but better calculated to be appreciated by cultivated minds than by the public, which had in former years granted him so wide a popularity. Most of these last compositions appeared in the weekly paper _L'Illustration_. In 1857 he published in one volume the series entitled _Masques et visages_ (1 vol. 12mo), and in 1869, about two years after his death, his last artistic work, _Les Douze Mois_ (1 vol. fol.), was given to the world. Gavarni was much engaged, during the last period of his life, in scientific pursuits, and this fact must perhaps be connected with the great change which then took place in his manner as an artist. He sent several communications to the Académie des Sciences, and till his death on the 23rd of November 1866 he was eagerly interested in the question of aerial navigation. It is said that he made experiments on a large scale with a view to find the means of directing balloons; but it seems that he was not so successful in this line as his fellow-artist, the caricaturist and photographer, Nadar.

Gavarni's _Oeuvres choisies_ were edited in 1845 (4 vols. 4to) with letterpress by J. Janin, Th. Gautier and Balzac, followed in 1850 by two other volumes named _Perles et parures_; and some essays in prose and in verse written by him were collected by one of his biographers, Ch. Yriarte, and published in 1869. See also E. and J. de Goncourt, _Gavarni, l'homme et l'oeuvre_ (1873, 8vo). J. Claretie has also devoted to the great French caricaturist a curious and interesting essay. A catalogue _raisonné_ of Gavarni's works was published by J. Armelhault and E. Bocher (Paris, 1873, 8vo).

GAVAZZI, ALESSANDRO (1809-1889), Italian preacher and patriot, was born at Bologna on the 21st of March 1809. He at first became a monk (1825), and attached himself to the Barnabites at Naples, where he afterwards (1829) acted as professor of rhetoric. In 1840, having already expressed liberal views, he was removed to Rome to fill a subordinate position. Leaving his own country after the capture of Rome by the French, he carried on a vigorous campaign against priests and Jesuits in England, Scotland and North America, partly by means of a periodical, the _Gavazzi Free Word_. While in England he gradually went over (1855) to the Evangelical church, and became head and organizer of the Italian Protestants in London. Returning to Italy in 1860, he served as army-chaplain with Garibaldi. In 1870 he became head of the Free Church (_Chiesa libera_) of Italy, united the scattered Congregations into the "Unione delle Chiese libere in Italia," and in 1875 founded in Rome the theological college of the Free Church, in which he himself taught dogmatics, apologetics and polemics. He died in Rome on the 9th of January 1889.

Amongst his publications are _No Union with Rome_ (1871); _The Priest in Absolution_ (1877); _My Recollections of the Last Four Popes_, &c., in answer to Cardinal Wiseman (1858); _Orations_, 2 decades (1851).

GAVELKIND,[1] a peculiar system of tenure associated chiefly with the county of Kent, but found also in other parts of England. In Kent all land is presumed to be holden by this tenure until the contrary is proved, but some lands have been disgavelled by particular statutes. It is more correctly described as socage tenure, subject to the custom of gavelkind. The chief peculiarities of the custom are the following. (1) A tenant can alienate his lands by feoffment at fifteen years of age. (2) There is no escheat on attainder for felony, or as it is expressed in the old rhyme--

"The father to the bough, The son to the plough."

(3) Generally the tenant could always dispose of his lands by will. (4) In case of intestacy the estate descends not to the eldest son but to all the sons (or, in the case of deceased sons, their representatives) in equal shares. "Every son is as great a gentleman as the eldest son is." It is to this remarkable peculiarity that gavelkind no doubt owes its local popularity. Though females claiming in their own right are postponed to males, yet by representation they may inherit together with them. (5) A wife is dowable of one-half, instead of one-third of the land. (6) A widower may be tenant by courtesy, without having had any issue, of one-half, but only so long as he remains unmarried. An act of 1841, for commuting manorial rights in respect of lands of copyhold and customary tenure, contained a clause specially exempting from the operation of the act "the custom of gavelkind as the same now exists and prevails in the county of Kent." Gavelkind is one of the most interesting examples of the customary law of England; it was, previous to the Conquest, the general custom of the realm, but was then superseded by the feudal law of primogeniture. Its survival in this instance in one part of the country is regarded as a concession extorted from the Conqueror by the superior bravery of the men of Kent. _Irish gavelkind_ was a species of tribal succession, by which the land, instead of being divided at the death of the holder amongst his sons, was thrown again into the common stock, and redivided among the surviving members of the sept. The equal division amongst children of an inheritance in land is of common occurrence outside the United Kingdom and is discussed under SUCCESSION.

See INHERITANCE; TENURE. Also Robinson, _On Gavelkind_; Digby, _History of the Law of Real Property_; Pollock and Maitland, _History of English Law_; Challis, _Real Property_.

FOOTNOTE:

[1] This word is generally taken to represent in O. Eng. _gafolgecynd_, from _gafol_, payment, tribute, and _gecynd_, species, kind, and originally to have meant tenure by payment of rent or non-military services, cf. gafol-land, and thence to have been applied to the particular custom attached to such tenure in Kent. _Gafol_ apparently is derived from the Teutonic root seen in "to give"; the Med. Lat. _gabulum, gablum_ gives the Fr. _gabelle_, tax.

GAVESTON, PIERS (d. 1312), earl of Cornwall, favourite of the English king Edward II., was the son of a Gascon knight, and was brought up at the court of Edward I. as companion to his son, the future king. Strong, talented and ambitious, Gaveston gained great influence over young Edward, and early in 1307 he was banished from England by the king; but he returned after the death of Edward I. a few months later, and at once became the chief adviser of Edward II. Made earl of Cornwall, he received both lands and money from the king, and added to his wealth and position by marrying Edward's niece, Margaret, daughter of Gilbert de Clare, earl of Gloucester (d. 1295). He was regent of the kingdom during the king's short absence in France in 1308, and took a very prominent part at Edward's coronation in February of this year. These proceedings aroused the anger and jealousy of the barons, and their wrath was diminished neither by Gaveston's superior skill at the tournament, nor by his haughty and arrogant behaviour to themselves. They demanded his banishment; and the king, forced to assent, sent his favourite to Ireland as lieutenant, where he remained for about a year. Returning to England in July 1309, Edward persuaded some of the barons to sanction this proceeding; but as Gaveston was more insolent than ever the old jealousies soon broke out afresh. In 1311 the king was forced to agree to the election of the "ordainers," and the ordinances they drew up provided _inter alia_ for the perpetual banishment of his favourite. Gaveston then retired to Flanders, but returned secretly to England at the end of 1311. Soon he was publicly restored by Edward, and the barons had taken up arms. Deserted by the king he surrendered to Aymer de Valence, earl of Pembroke (d. 1324), at Scarborough in May 1312, and was taken to Deddington in Oxfordshire, where he was seized by Guy de Beauchamp, earl of Warwick (d. 1315). Conveyed to Warwick castle he was beheaded on Blacklow Hill near Warwick on the 19th of June 1312. Gaveston, whose body was buried in 1315 at King's Langley, left an only daughter.

See W. Stubbs, _Constitutional History_, vol. ii. (Oxford, 1896); and _Chronicles of the Reigns of Edward I. and Edward II._, edited by W. Stubbs. Rolls series (London, 1882-1883).

GAVOTTE (a French word adopted from the Provençal _gavoto_), properly the dance of the Gavots or natives of Gap, a district in the Upper Alps, in the old province of Dauphiné. It is a dance of a brisk and lively character, somewhat resembling the minuet, but quicker and less stately (see DANCE); hence also the use of this name for a corresponding form of musical composition.

GAWAIN (Fr. _Walwain (Brut), Gauvain, Gaugain_; Lat. _Walganus_, _Walwanus_; Dutch, _Walwein_, Welsh, _Gwalchmei_), son of King Loth of Orkney, and nephew to Arthur on his mother's side, the most famous hero of Arthurian romance. The first mention of his name is in a passage of William of Malmesbury, recording the discovery of his tomb in the province of Ros in Wales. He is there described as "_Walwen qui fuit haud degener Arturis ex sorore nepos_." Here he is said to have reigned over Galloway; and there is certainly some connexion, the character of which is now not easy to determine, between the two. In the later _Historia_ of Geoffrey of Monmouth, and its French translation by Wace, Gawain plays an important and "pseudo-historic" rôle. On the receipt by Arthur of the insulting message of the Roman emperor, demanding tribute, it is he who is despatched as ambassador to the enemy's camp, where his arrogant and insulting behaviour brings about the outbreak of hostilities. On receipt of the tidings of Mordred's treachery, Gawain accompanies Arthur to England, and is slain in the battle which ensues on their landing. Wace, however, evidently knew more of Gawain than he has included in his translation, for he speaks of him as

Li quens Walwains Qui tant fu preudom de ses mains (11. 9057-58).

and later on says

Prous fu et de mult grant mesure, D'orgoil et de forfait n'ot qure Plus vaut faire qu'il ne dist Et plus doner qu'il ne pramist (10. 106-109).

The English Arthurian poems regard him as the type and model of chivalrous courtesy, "the fine father of nurture," and as Professor Maynadier has well remarked, "previous to the appearance of Malory's compilation it was Gawain rather than Arthur, who was the typical English hero." It is thus rather surprising to find that in the earliest preserved MSS. of Arthurian romance, i.e. in the poems of Chrétien de Troyes, Gawain, though generally placed first in the list of knights, is by no means the hero _par excellence_. The latter part of the _Perceval_ is indeed devoted to the recital of his adventures at the _Chastel Merveilleus_, but of none of Chrétien's poems is he the protagonist. The anonymous author of the _Chevalier à l'epée_ indeed makes this apparent neglect of Gawain a ground of reproach against Chrétien. At the same time the majority of the short episodic poems connected with the cycle have Gawain for their hero. In the earlier form of the prose romances, e.g. in the _Merlin_ proper, Gawain is a dominant personality, his feats rivalling in importance those ascribed to Arthur, but in the later forms such as the _Merlin_ continuations, the _Tristan_, and the final _Lancelot_ compilation, his character and position have undergone a complete change, he is represented as cruel, cowardly and treacherous, and of indifferent moral character. Most unfortunately our English version of the romances, Malory's _Morte Arthur_, being derived from these later forms (though his treatment of Gawain is by no means uniformly consistent), this unfavourable aspect is that under which the hero has become known to the modern reader. Tennyson, who only knew the Arthurian story through the medium of Malory, has, by exaggeration, largely contributed to this misunderstanding. Morris, in _The Defence of Guinevere_, speaks of "gloomy Gawain"; perhaps the most absurdly misleading epithet which could possibly have been applied to the "gay, gratious, and gude" knight of early English tradition.

The truth appears to be that Gawain, the Celtic and mythic origin of whose character was frankly admitted by the late M. Gaston Paris, belongs to the very earliest stage of Arthurian tradition, long antedating the crystallization of such tradition into literary form. He was certainly known in Italy at a very early date; Professor Rajna has found the names of Arthur and Gawain in charters of the early 12th century, the bearers of those names being then grown to manhood; and Gawain is figured in the architrave of the north doorway of Modena cathedral, a 12th-century building. Recent discoveries have made it practically certain that there existed, prior to the extant romances, a collection of short episodic poems, devoted to the glorification of Arthur's famous nephew and his immediate kin (his brother Ghaeris, or Gareth, and his son Guinglain), the authorship of which was attributed to a Welshman, Bleheris; fragments of this collection have been preserved to us alike in the first continuation of Chrétien de Troyes _Perceval_, due to Wauchier de Denain, and in our vernacular _Gawain_ poems. Among these "Bleheris" poems was one dealing with Gawain's adventures at the Grail castle, where the Grail is represented as non-Christian, and presents features strongly reminiscent of the ancient Nature mysteries. There is good ground for believing that as Grail quester and winner, Gawain preceded alike Perceval and Galahad, and that the solution of the mysterious Grail problem is to be sought rather in the tales connected with the older hero than in those devoted to the glorification of the younger knights. The explanation of the very perplexing changes which the character of Gawain has undergone appears to lie in a misunderstanding of the original sources of that character. Whether or no Gawain was a sun-hero, and he certainly possessed some of the features--we are constantly told how his strength waxed with the waxing of the sun till noontide, and then gradually decreased; he owned a steed known by a definite name le Gringalet; and a light-giving sword, Escalibur (which, as a rule, is represented as belonging to Gawain, not to Arthur)--all traits of a sun-hero--he certainly has much in common with the primitive Irish hero Cuchullin. The famous head-cutting challenge, so admirably told in _Syr Gawayne and the Grene Knighte_, was originally connected with the Irish champion. Nor was the lady of Gawain's love a mortal maiden, but the queen of the other-world. In Irish tradition the other-world is often represented as an island, inhabited by women only; and it is this "Isle of Maidens" that Gawain visits in _Diu Crone_; returning therefrom dowered with the gift of eternal youth. The Chastel Merveilleus adventure, related at length by Chrétien and Wolfram is undoubtedly such an "other-world" story. It seems probable that it was this connexion which won for Gawain the title of the "Maidens' Knight," a title for which no satisfactory explanation is ever given. When the source of the name was forgotten its meaning was not unnaturally misinterpreted, and gained for Gawain the reputation of a facile morality, which was exaggerated by the pious compilers of the later Grail romances into persistent and aggravated wrong-doing; at the same time it is to be noted that Gawain is never like Tristan and Lancelot, the hero of an illicit connexion maintained under circumstances of falsehood and treachery. Gawain, however, belonged to the pre-Christian stage of Grail tradition, and it is not surprising that writers, bent on spiritual edification, found him somewhat of a stumbling-block. Chaucer, when he spoke of Gawain coming "again out of faërie," spoke better than he knew; the home of that very gallant and courteous knight is indeed Fairy-land, and the true Gawain-tradition is informed with fairy glamour and grace.

See _Syr Gawayne_, the English poems relative to that hero, edited by Sir Frederick Madden for the Bannatyne Club, 1839 (out of print and difficult to procure); _Histoire littéraire de la France_, vol. xxx.; introduction and summary of episodic "Gawain" poems by Gaston Paris; _The Legend of Sir Gawain_, by Jessie L. Weston, Grimm Library, vol. vii.; _The Legend of Sir Perceval_, by Jessie L. Weston, Grimm Library, vol. xvii.; "Sir Gawain and the Green Knight," "Sir Gawain at the Grail Castle" and "Sir Gawain and the Lady of Lys," vols. i., vi and vii. of _Arthurian Romances_ (Nutt).

GAWLER, a town of Gawler county, South Australia, on the Para river, 24¾ m. by rail N.E. of Adelaide. It is one of the most thriving places in the colony, being the centre of a large wheat-growing district; it has also engineering works, foundries, flour-mills, breweries and saw-mills, while gold, silver, copper and lead are found in the neighbouring hills. The inhabitants of the town and its extensive suburbs number about 7000; though the population of the town itself in 1901 was 1996.

GAY, JOHN (1685-1732), English poet, was baptized on the 16th of September 1685 at Barnstaple, where his family had long been settled. He was educated at the grammar school of the town under Robert Luck, who had published some Latin and English poems. On leaving school he was apprenticed to a silk mercer in London, but being weary, according to Dr Johnson, "of either the restraint or the servility of his occupation," he soon returned to Barnstaple, where he spent some time with his uncle, the Rev. John Hanmer, the Nonconformist minister of the town. He then returned to London, and though no details are available for his biography until the publication of _Wine_ in 1708, the account he gives in _Rural Sports_ (1713), of years wasted in attending on courtiers who were profuse in promises never kept, may account for his occupations. Among his early literary friends were Aaron Hill and Eustace Budgell. In _The Present State of Wit_ (1711) Gay attempted to give an account of "all our periodical papers, whether monthly, weekly or diurnal." He especially praised the _Tatler_ and the _Spectator_, and Swift, who knew nothing of the authorship of the pamphlet, suspected it to be inspired by Steele and Addison. To Lintot's _Miscellany_ (1712) Gay contributed "An Epistle to Bernard Lintot," containing some lines in praise of Pope, and a version of the story of Arachne from the sixth book of the _Metamorphoses_ of Ovid. In the same year he was received into the household of the duchess of Monmouth as secretary, a connexion which was, however, broken before June 1714.

The dedication of his _Rural Sports_ (1713) to Pope was the beginning of a lasting friendship. Gay could have no pretensions to rivalry with Pope, who seems never to have tired of helping his friend. In 1713 he produced a comedy, _The Wife of Bath_, which was acted only three nights, and _The Fan_, one of his least successful poems; and in 1714 _The Shepherd's Week_, a series of six pastorals drawn from English rustic life. Pope had urged him to undertake this last task in order to ridicule the Arcadian pastorals of Ambrose Philips, who had been praised by the _Guardian_, to the neglect of Pope's claims as the first pastoral writer of the age and the true English Theocritus. Gay's pastorals completely achieved this object, but his ludicrous pictures of the English swains and their loves were found to be abundantly entertaining on their own account. Gay had just been appointed secretary to the British ambassador to the court of Hanover through the influence of Jonathan Swift, when the death of Queen Anne three months later put an end to all his hopes of official employment. In 1715, probably with some help from Pope, he produced _What d'ye call it?_ a dramatic skit on contemporary tragedy, with special reference to Otway's _Venice Preserved_. It left the public so ignorant of its real meaning that Lewis Theobald and Benjamin Griffin (1680-1740) published a _Complete Key to what d'ye call it_ by way of explanation. In 1716 appeared his _Trivia, or the Art of Walking the Streets of London_, a poem in three books, for which he acknowledged having received several hints from Swift. It contains graphic and humorous descriptions of the London of that period. In January 1717 he produced the comedy of _Three Hours after Marriage_, which was grossly indecent without being amusing, and was a complete failure. There is no doubt that in this piece he had assistance from Pope and Arbuthnot, but they were glad enough to have it assumed that Gay was the sole author.

Gay had numerous patrons, and in 1720 he published _Poems on Several Occasions_ by subscription, realizing £1000 or more. In that year James Craggs, the secretary of state, presented him with some South Sea stock. Gay, disregarding the prudent advice of Pope and other of his friends, invested his all in South Sea stock, and, holding on to the end, he lost everything. The shock is said to have made him dangerously ill. As a matter of fact Gay had always been a spoilt child, who expected everything to be done for him. His friends did not fail him at this juncture. He had patrons in William Pulteney, afterwards earl of Bath, in the third earl of Burlington, who constantly entertained him at Chiswick or at Burlington House, and in the third earl of Queensberry. He was a frequent visitor with Pope, and received unvarying kindness from Congreve and Arbuthnot. In 1724 he produced a tragedy called _The Captives_. In 1727 he wrote for Prince William, afterwards duke of Cumberland, his famous _Fifty-one Fables in Verse_, for which he naturally hoped to gain some preferment, although he has much to say in them of the servility of courtiers and the vanity of court honours. He was offered the situation of gentleman-usher to the Princess Louisa, who was still a child. He refused this offer, which all his friends seem to have regarded, for no very obvious reason, as an indignity. As the _Fables_ were written for the amusement of one royal child, there would appear to have been a measure of reason in giving him a sinecure in the service of another. His friends thought him unjustly neglected by the court, but he had already received (1722) a sinecure as lottery commissioner with a salary of £150 a year, and from 1722 to 1729 he had lodgings in the palace at Whitehall. He had never rendered any special services to the court.

He certainly did nothing to conciliate the favour of the government by his next production, the _Beggars' Opera_, a lyrical drama produced on the 29th of January 1728 by Rich, in which Sir Robert Walpole was caricatured. This famous piece, which was said to have made "Rich gay and Gay rich," was an innovation in many respects, and for a time it drove Italian opera off the English stage. Under cover of the thieves and highwaymen who figured in it was disguised a satire on society, for Gay made it plain that in describing the moral code of his characters he had in mind the corruptions of the governing class. Part of the success of the _Beggars' Opera_ may have been due to the acting of Lavinia Fenton, afterwards duchess of Bolton, in the part of Polly Peachum. The play ran for sixty-two nights, though the representations, four of which were "benefits" of the author, were not, as has sometimes been stated, consecutive. Swift is said to have suggested the subject, and Pope and Arbuthnot were constantly consulted while the work was in progress, but Gay must be regarded as the sole author. He wrote a sequel, _Polly_, the representation of which was forbidden by the lord chamberlain, no doubt through the influence of Walpole. This act of "oppression" caused no loss to Gay. It proved an excellent advertisement for _Polly_, which was published by subscription in 1729, and brought its author more than £1000. The duchess of Queensberry was dismissed from court for enlisting subscribers in the palace. The duke of Queensberry gave him a home, and the duchess continued her affectionate patronage until Gay's death, which took place on the 4th of December 1732. He was buried in Westminster Abbey. The epitaph on his tomb is by Pope, and is followed by Gay's own mocking couplet:--

"Life is a jest, and all things show it, I thought so once, and now I know it."

_Acis and Galatea_, an English pastoral opera, the music of which was written by Handel, was produced at the Haymarket in 1732. The profits of his posthumous opera of _Achilles_ (1733), and a new volume of _Fables_ (1738) went to his two sisters, who inherited from him a fortune of £6000. He left two other pieces, _The Distressed Wife_ (1743), a comedy, and _The Rehearsal at Goatham_ (1754), a farce. The _Fables_, slight as they may appear, cost him more labour than any of his other works. The narratives are in nearly every case original, and are told in clear and lively verse. The moral which rounds off each little story is never strained. They are masterpieces in their kind, and the very numerous editions of them prove their popularity. They have been translated into Latin, French and Italian, Urdu and Bengali.

See his _Poetical Works_ (1893) in the Muses' Library, with an introduction by Mr John Underhill; also Samuel Johnson's _Lives of the Poets_, John Gay's _Singspiele_ (1898), edited by G. Sarrazin (_Englische Textbibliothek II._); and an article by Austin Dobson in vol. 21 of the _Dictionary of National Biography_; _Gay's Chair_ (1820), edited by Henry Lee, a fellow-townsman, contained a biographical sketch by his nephew, the Rev. Joseph Baller.

GAY, MARIE FRANÇOISE SOPHIE (1776-1852), French author, was born in Paris on the 1st of July 1776. Madame Gay was the daughter of M. Nichault de la Valette and of Francesca Peretti, an Italian lady. In 1793 she was married to M. Liottier, an exchange broker, but she was divorced from him in 1799, and shortly afterwards was married to M. Gay, receiver-general of the department of the Roër or Ruhr. This union brought her into intimate relations with many distinguished personages; and her salon came to be frequented by all the distinguished littérateurs, musicians, actors and painters of the time, whom she attracted by her beauty, her vivacity and her many amiable qualities. Her first literary production was a letter written in 1802 to the _Journal de Paris_, in defence of Madame de Staël's novel, _Delphine_; and in the same year she published anonymously her first novel _Laure d'Estell_. _Léonie de Montbreuse_, which appeared in 1813, is considered by Sainte-Beuve her best work; but _Anatole_ (1815), the romance of a deaf-mute, has perhaps a higher reputation. Among her other works, _Salons célèbres_ (2 vols., 1837) may be especially mentioned. Madame Gay wrote several comedies and opera libretti which met with considerable success. She was also an accomplished musician, and composed both the words and music of a number of songs. She died in Paris on the 5th of March 1852. For an account of her daughter, Delphine Gay, Madame de Girardin, see GIRARDIN.

See her own _Souvenirs d'une vieille femme_ (1834); also Théophile Gautier, _Portraits contemporains_; and Sainte-Beuve, _Causeries du lundi_, vol. vi.

GAY, WALTER (1856- ), American artist, was born at Hingham, Massachusetts, on the 22nd of January 1856. In 1876 he became a pupil of Léon Bonnat in Paris. He received an honourable mention in the Salon of 1885; a gold medal in 1888, and similar awards at Vienna (1894), Antwerp (1895), Berlin (1896) and Munich (1897). He became an officer of the Legion of Honour and a member of the Society of Secession, Munich. Works by him are in the Luxembourg, the Tate Gallery (London), and the Boston and Metropolitan (New York) Museums of Art. His compositions are mainly figure subjects portraying French peasant life.

GAYA, a city and district of British India, in the Patna division of Bengal. The city is situated 85 m. S. of Patna by rail. Pop. (1901) 71,288. It consists of two distinct parts, adjoining each other; the part containing the residences of the priests is Gaya proper; and the other, which is the business quarter, is called Sahibganj. The civil offices and residences of the European inhabitants are situated here. Gaya derives its sanctity from incidents in the life of Buddha. But a local legend also exists concerning a pagan monster of great sanctity, named Gaya, who by long penance had become holy, so that all who saw or touched him were saved from perdition. Yama, the lord of hell, appealed to the gods, who induced Gaya to lie down in order that his body might be a place of sacrifice; and once down, Yama placed a large stone on him to keep him there. The tricked demon struggled violently, and, in order to pacify him, Vishnu promised that the gods should take up their permanent residence in him, and that any one who made a pilgrimage to the spot where he lay should be delivered from the terrors of the Hindu place of torment. This may possibly be a Brahmanic rendering of Buddha's life and work. There are forty-five sacred spots (of which the temple of Vishnupada is the chief) in and around the city, and these are visited by thousands of pilgrims annually. During the Mutiny the large store of treasure here was conveyed safely to Calcutta by Mr A. Money. The city contains a government high school and an hospital, with a Lady Elgin branch for women.

The DISTRICT OF GAYA comprises an area of 4712 sq. m. Generally speaking, it consists of a level plain, with a ridge of prettily wooded hills along the southern boundary, whence the country falls with a gentle slope towards the Ganges. Rocky hills occasionally occur, either detached or in groups, the loftiest being Maher hill about 12 m. S.E. of Gaya city, with an elevation of 1620 ft. above sea-level. The eastern part of the district is highly cultivated; the portions to the north and west are less fertile; while in the south the country is thinly peopled and consists of hills, the jungles on which are full of wild animals. The principal river is the Son, which marks the boundary between Gaya and Shahabad, navigable by small boats throughout the year, and by craft of 20-tons burden in the rainy season. Other rivers are the Punpun, Phalgu and Jamuna. Two branches of the Son canal system, the eastern main canal and the Patna canal, intersect the district. In 1901 the population was 2,059,933, showing a decrease of 3% in the decade. Among the higher castes there is an unusually large proportion of Brahmans, a circumstance due to the number of sacred places which the district contains. The Gayawals, or priests in charge of the holy places, are held in high esteem by the pilgrims; but they are not pure Brahmans, and are looked down upon by those who are. They live an idle and dissolute life, but are very wealthy, from contributions extorted from the pilgrims. Buddh Gaya, about 6 m. S. of Gaya city, is one of the holiest sites of Buddhism, as containing the tree under which Sakyamuni attained enlightenment. In addition to many ruins and sculptures, there is a temple restored by the government in 1881. Another place of religious interest is a temple of great antiquity, which crowns the highest peak of the Barabar hills, and at which a religious fair is held each September, attended by 10,000 to 20,000 pilgrims. At the foot of the hill are numerous rock caves excavated about 200 B.C. The opium poppy is largely cultivated. There are a number of lac factories. Manufactures consist of common brass utensils, black stone ornaments, pottery, tussur-silk and cotton cloth. Formerly paper-making was an important manufacture in the district, but it has entirely died out. The chief exports are food grains, oil seeds, indigo, crude opium (sent to Patna for manufacture), saltpetre, sugar, blankets, brass utensils, &c. The imports are salt, piece goods, cotton, timber, bamboos, tobacco, lac, iron, spices and fruits. The district is traversed by four branches of the East Indian railway. In 1901 it suffered severely from the plague.

See _District Gazetteer_ (1906); Sir A. Cunningham, _Mahabodhi_ (1892).

GAYAL, a domesticated ox allied to the Gaur, but distinguished, among other features, by the more conical and straighter horns, and the straight line between them. Gayal are kept by the natives of the hill-districts of Assam and parts of Tenasserim and Upper Burma. Although it has received a distinct name, _Bos (Bibos) frontalis_, there can be little doubt that the gayal is merely a domesticated breed of the gaur, many gayal-skulls showing characters approximating to those of the gaur.

GAYANGOS Y ARCE, PASCUAL DE (1809-1897), Spanish scholar and Orientalist, was born at Seville on the 21st of June 1809. At the age of thirteen he was sent to be educated at Pont-le-Voy near Blois, and in 1828 began the study of Arabic under Silvestre de Sacy. After a visit to England, where he married, he obtained a post in the Spanish treasury, and was transferred to the foreign office as translator in 1833. In 1836 he returned to England, wrote extensively in English periodicals, and translated Almakkari's _History of the Mahommedan Dynasties in Spain_ (1840-1843) for the Royal Asiatic Society. In England he also made the acquaintance of Ticknor, to whom he was very serviceable. In 1843 he returned to Spain as professor of Arabic at the university of Madrid, which post he held until 1881, when he was made director of public instruction. This office he resigned upon being elected senator for the district of Huelva. His latter years were spent in cataloguing the Spanish manuscripts in the British Museum; he had previously continued Bergenroth's catalogue of the manuscripts relating to England in the Simancas archives. His best-known original work is his dissertation on Spanish romances of chivalry in Rivadeneyra's _Biblioteca de autores españoles_. He died in London on the 4th of October 1897.

GAYARRÉ, CHARLES ÉTIENNE ARTHUR (1805-1895), American historian, was born in New Orleans, Louisiana, on the 9th of January 1805. After studying at the Collège d'Orléans he began, in 1826, to study law in Philadelphia, and three years later was admitted to the bar. In 1830 he was elected a member of the House of Representatives of Louisiana, in 1831 was appointed deputy attorney-general of his state, in 1833 became presiding judge of the city court of New Orleans, and in 1834 was elected as a Jackson Democrat to the United States Senate. On account of ill-health, however, he immediately resigned without taking his seat, and for the next eight years travelled in Europe and collected historical material from the French and the Spanish archives. In 1844-1845 and in 1856-1857 he was again a member of the state House of Representatives, and from 1845 to 1853 was secretary of state of Louisiana. He supported the Southern Confederacy during the Civil War, in which he lost a large fortune, and after its close lived chiefly by his pen. He died in New Orleans on the 11th of February 1895. He is best known as the historian of Louisiana. He wrote _Histoire de la Louisiane_ (1847); _Romance of the History of Louisiana_ (1848); _Louisiana: its Colonial History and Romance_ (1851), reprinted in _A History of Louisiana_; _History of Louisiana: the Spanish Domination_ (1854); _Philip II. of Spain_ (1866); and _A History of Louisiana_ (4 vols., 1866), the last being a republication and continuation of his earlier works in this field, the whole comprehending the history of Louisiana from its earliest discovery to 1861. He wrote also several dramas and romances, the best of the latter being _Fernando de Lemos_ (1872).

GAY-LUSSAC, JOSEPH LOUIS (1778-1850), French chemist and physicist, was born at St Léonard, in the department of Haute Vienne, on the 6th of December 1778. He was the elder son of Antoine Gay, _procureur du roi_ and judge at Pont-de-Noblac, who assumed the name Lussac from a small property he had in the neighbourhood of St Léonard. Young Gay-Lussac received his early education at home under the direction of the abbé Bourdieux and other masters, and in 1794 was sent to Paris to prepare for the École Polytechnique, into which he was admitted at the end of 1797 after a brilliant examination. Three years later he was transferred to the École des Ponts et Chaussées, and shortly afterwards was assigned to C.L. Berthollet, who wanted an able student to help in his researches. The new assistant scarcely came up to expectations in respect of confirming certain theoretical views of his master's by the experiments set him to that end, and appears to have stated the discrepancy without reserve; but Berthollet nevertheless quickly recognized the ability displayed, and showed his appreciation not only by desiring to be Gay-Lussac's "father in science," but also by making him in 1807 an original member of the Société d'Arcueil. In 1802 he was appointed demonstrator to A.F. Fourcroy at the École Polytechnique, where subsequently (1809) he became professor of chemistry, and from 1808 to 1832 he was professor of physics at the Sorbonne, a post which he only resigned for the chair of chemistry at the Jardin des Plantes. In 1831 he was elected to represent Haute Vienne in the chamber of deputies, and in 1839 he entered the chamber of peers. He died in Paris on the 9th of May 1850.

Gay-Lussac's earlier researches were mostly physical in character and referred mainly to the properties of gases, vapour-tensions, hygrometry, capillarity, &c. In his first memoir (_Ann. de Chimie_, 1802) he showed that different gases are dilated in the same proportion when heated from 0° to 100° C. Apparently he did not know of Dalton's experiments on the same point, which indeed were far from accurate; but in a note he explained that "le cit. Charles avait remarqué depuis 15 ans la même propriété dans ces gaz; mais n'ayant jamais publié ses résultats, c'est par le plus grand hasard que je les ai connus." In consequence of his candour in thus rescuing from oblivion the observation which his fellow-citizen did not think worth publishing, his name is sometimes dissociated from this law, which instead is known as that of Charles. In 1804 he had an opportunity of prosecuting his researches on air in somewhat unusual conditions, for the French Academy, desirous of securing some observations on the force of terrestrial magnetism at great elevations above the earth, through Berthollet and J.E. Chaptal obtained the use of the balloon which had been employed in Egypt, and entrusted the task to him and J.B. Biot. In their first ascent from the garden of the Conservatoire des Arts on the 24th of August 1804 an altitude of 4000 metres (about 13,000 ft.) was attained. But this elevation was not considered sufficient by Gay-Lussac, who therefore made a second ascent by himself oh the 16th of September, when the balloon rose 7016 metres (about 23,000 ft.) above sea-level. At this height, with the thermometer marking 9½ degrees below freezing, he remained for a considerable time, making observations not only on magnetism, but also on the temperature and humidity of the air, and collecting several samples of air at different heights. The magnetic observations, though imperfect, led him to the conclusion that the magnetic effect at all attainable elevations above the earth's surface remains constant; and on analysing the samples of air he could find no difference of composition at different heights. (For an account of both ascents see _Journ. de phys._ for 1804.) On the 1st of October in the same year, in conjunction with Alexander von Humboldt, he read a paper on eudiometric analysis (_Ann. de Chim._, 1805), which contained the germ of his most important generalization, the authors noting that when oxygen and hydrogen combine together by volume, it is in the proportion of one volume of the former to two volumes of the latter. But his law of combination by volumes was not enunciated in its general form until after his return from a scientific journey through Switzerland, Italy and Germany, on which with Humboldt he started from Paris in March 1805. This journey was interrupted in the spring of 1806 by the news of the death of M.J. Brisson, and Gay-Lussac hurried back to Paris in the hope, which was gratified, that he would be elected to the seat thus vacated in the Academy. In 1807 an account of the magnetic observations made during the tour with Humboldt was published in the first volume of the _Mémoires d'Arcueil_, and the second volume, published in 1809, contained the important memoir on gaseous combination (read to the Société Philomathique on the last day of 1808), in which he pointed out that gases combining with each other in volume do so in the simplest proportions--1 to 1, 1 to 2, 1 to 3--and that the volume of the compound formed bears a simple ratio to that of the constituents.

About this time Gay-Lussac's work, although he by no means entirely abandoned physical questions, became of a more chemical character; and in three instances it brought him into direct rivalry with Sir Humphry Davy. In the first case Davy's preparation of potassium and sodium by the electric current spurred on Gay-Lussac and his collaborator L.J. Thénard, who had no battery at their disposal, to search for a chemical method of obtaining those metals, and by the action of red-hot iron on fused potash--a method of which Davy admitted the advantages--they succeeded in 1808 in preparing potassium, going on to make a full study of its properties and to use it, as Davy also did, for the reduction of boron from boracic acid in 1809. The second concerned the nature of "oxymuriatic acid" (chlorine). While admitting the possibility that it was an elementary body, after many experiments they finally declared it to be a compound (_Mém. d'Arcueil_, 1809). Davy, on the other hand, could see no reason to suppose it contained oxygen, as they surmised, and ultimately they had to accept his view of its elementary character. The third case roused most feeling of all. Davy, passing through Paris on his way to Italy at the end of 1813, obtained a few fragments of iodine, which had been discovered by Bernard Courtois (1777-1838) in 1811, and after a brief examination by the aid of his limited portable laboratory perceived its analogy to chlorine and inferred it to be an element. Gay-Lussac, it is said, was nettled at the idea of a foreigner making such a discovery in Paris, and vigorously took up the study of the new substance, the result being the "Mémoire sur l'iode," which appeared in the _Ann. de chim._ in 1814. He too saw its resemblance to chlorine, and was obliged to agree with Davy's opinion as to its simple nature, though not without some hesitation, due doubtless to his previous declaration about chlorine. Davy on his side seems to have felt that the French chemist was competing with him, not altogether fairly, in trying to appropriate the honour of discovering the character of the substance and of its compound, hydriodic acid.

In 1810 he published a paper which contains some classic experiments on fermentation, a subject to which he returned in a second paper published in 1815. At the same time he was working with Thénard at the improvement of the methods of organic analysis, and by combustion with oxidizing agents, first potassium chlorate and subsequently copper oxide, he determined the composition of a number of organic substances. But his last great piece of pure research was on prussic acid. In a note published in 1811 he described the physical properties of this acid, but he said nothing about its chemical composition till 1815, when he described cyanogen as a compound radicle, prussic acid as a compound of that radicle with hydrogen alone, and the prussiates (cyanides) as compounds of the radicle with metals. The proof that prussic acid contains hydrogen but no oxygen was a most important support to the hydrogen-acid theory, and completed the downfall of Lavoisier's oxygen theory; while the isolation of cyanogen was of equal importance for the subsequent era of compound radicles in organic chemistry.

After this research Gay-Lussac's attention began to be distracted from purely scientific investigation. He had now secured a leading if not the foremost place among the chemists of the French capital, and the demand for his services as adviser in technical problems and matters of practical interest made great inroads on his available time. He had been a member of the consultative committee on arts and manufactures since 1805; he was attached to the "administration des poudres et salpêtres" in 1818, and in 1829 he received the lucrative post of assayer to the mint. In these new fields he displayed the powers so conspicuous in his scientific inquiries, and he was now to introduce and establish scientific accuracy where previously there had been merely practical approximations. His services to industry included his improvements in the processes for the manufacture of sulphuric acid (1818) and oxalic acid (1829); methods of estimating the amount of real alkali in potash and soda by the volume of standard acid required for neutralization, and for estimating the available chlorine in bleaching powder by a solution of arsenious acid; directions for the use of the centesimal alcoholometer published in 1824 and specially commended by the Institute; and the elaboration of a method of assaying silver by a standard solution of common salt, a volume on which was published in 1833. Among his research work of this period may be mentioned the improvements in organic analysis and the investigation of fulminic acid made with the help of Liebig, who gained the privilege of admission to his private laboratory in 1823-1824.

Gay-Lussac was patient, persevering, accurate to punctiliousness, perhaps a little cold and reserved, and not unaware of his great ability. But he was also bold and energetic, not only in his work but also in support and defence of his friends. His early childish adventures, as told by Arago, herald the fearless aeronaut and the undaunted investigator of volcanic eruptions (Vesuvius was in full eruption when he visited it during his tour in 1805); and the endurance he exhibited under the laboratory accidents that befell him shows the power of will with which he would face the prospect of becoming blind and useless for the prosecution of the science which was his very life, and of which he was one of the most distinguished ornaments. Only at the very end, when the disease from which he was suffering left him no hope, did he complain with some bitterness of the hardship of leaving this world where the many discoveries being made pointed to yet greater discoveries to come.

The most complete list of Gay-Lussac's papers is contained in the Royal Society's _Catalogue of Scientific Papers_, which enumerates 148, exclusive of others written jointly with Humboldt, Thénard, Welter and Liebig. Many of them were published in the _Annales de chimie_, which after it changed its title to _Annales de chimie et physique_ he edited, with Arago, up to nearly the end of his life; but some are to be found in the _Mémoires d'Arcueil_ and the _Comptes rendus_, and in the _Recherches physiques et chimiques_, published with Thénard in 1811.

GAZA, THEODORUS (c. 1400-1475), one of the Greek scholars who were the leaders of the revival of learning in the 15th century, was born at Thessalonica. On the capture of his native city by the Turks in 1430 he fled to Italy. During a three years' residence in Mantua he rapidly acquired a competent knowledge of Latin under the teaching of Vittorino da Feltre, supporting himself meanwhile by giving lessons in Greek, and by copying manuscripts of the ancient classics.[1] In 1447 he became professor of Greek in the newly founded university of Ferrara, to which students in great numbers from all parts of Italy were soon attracted by his fame as a teacher. He had taken some part in the councils which were held in Siena (1423), Ferrara (1438), and Florence (1439), with the object of bringing about a reconciliation between the Greek and Latin Churches; and in 1450, at the invitation of Pope Nicholas V., he went to Rome, where he was for some years employed by his patron in making Latin translations from Aristotle and other Greek authors. After the death of Nicholas (1455), being unable to make a living at Rome, Gaza removed to Naples, where he enjoyed the patronage of Alphonso the Magnanimous for two years (1456-1458). Shortly afterwards he was appointed by Cardinal Bessarion to a benefice in Calabria, where the later years of his life were spent, and where he died about 1475. Gaza stood high in the opinion of most of his learned contemporaries, but still higher in that of the scholars of the succeeding generation. His Greek grammar (in four books), written in Greek, first printed at Venice in 1495, and afterwards partially translated by Erasmus in 1521, although in many respects defective, especially in its syntax, was for a long time the leading text-book. His translations into Latin were very numerous, including the _Problemata_, _De partibus animalium_ and _De generatione animalium_ of Aristotle; the _Historia plantarum_ of Theophrastus; the _Problemata_ of Alexander Aphrodisias; the _De instruendis aciebus_ of Aelian; the _De compositione verborum_ of Dionysius of Halicarnassus; and some of the _Homilies_ of John Chrysostom. He also turned into Greek Cicero's _De senectute_ and _Somnium Scipionis_--with much success, in the opinion of Erasmus; with more elegance than exactitude, according to the colder judgment of modern scholars. He was the author also of two small treatises entitled _De mensibus_ and _De origine Turcarum_.

See G. Voigt, _Die Wiederbelebung des klassischen Altertums_ (1893), and article by C.F. Bähr in Ersch and Gruber's _Allgemeine Encyklopädie_. For a complete list of his works, see Fabricius, _Bibliotheca Graeca_ (ed. Harles), x.

FOOTNOTE:

[1] According to Voigt, Gaza came to Italy some ten years later from Constantinople, where he had been a teacher or held some clerical office.

GAZA (or 'AZZAH, mod. _Ghuzzeh_), the most southerly of the five princely Philistine cities, situated near the sea, at the point where the old trade routes from Egypt, Arabia and Petra to Syria met. It was always a strong border fortress and a place of commercial importance, in many respects the southern counterpart of Damascus. The earliest notice of it is in the Tell el-Amarna tablets, in a letter from the local governor, who then held it for Egypt, with which country it always stood in close connexion. It never passed for long into Israelite hands, though subject for a while to Hezekiah of Judah; from him it passed to Assyria. In Amos i. 6 the city is denounced for giving up Hebrew slaves to Edom. To Herodotus (iii. 5) the place seemed as important as Sardis. The city withstood Alexander the Great for five months (332 B.C.), and in 96 B.C. was razed to the ground by Alexander Jannaeus. It was rebuilt by Aulus Gabinius, 57 B.C., but on a new site; the old site was remembered and spoken of as "Old" or "Desert Gaza": compare Acts viii. 26. In the 2nd and 3rd centuries Gaza was a thriving Greek city, with good schools and famous temples, especially one to the local god Marna (i.e. "Lord" or "Our Lord"). A statue of this god has been found near Gaza; it much resembles the Greek representation of Zeus. The struggle with Christianity here was long and intense. Egyptian monks gradually won over the country folk, and in 402, under the influence of Theodosius and Porphyry the local bishop, the Marneion was destroyed and the cross made politically supreme. In the 5th and 6th centuries Gaza was held in high repute as a place of learning. But after it passed into Moslem hands (635) it gradually lost all save commercial importance, and even the Crusaders did little to revive its old military glory. It finally was captured by the Moslems in 1244. Napoleon captured it in 1799.

The modern town (pop. 16,000) is divided into four quarters, one of which is built on a low hill. A magnificent grove of very ancient olives forms an avenue 4 m. long to the north. There are many lofty minarets in various parts of the town, and a fine mosque built of ancient materials. A 12th century church towards the south side of the hill has also been converted into a mosque. On the east is shown the tomb of Samson (an erroneous tradition dating back to the middle ages). The ancient walls are now covered up beneath green mounds of rubbish. The water-supply is from wells sunk through the sandy soil to the rock; of these there are more than twenty--an unusual number for a Syrian town. The land for the 3 m. between Gaza and the sea consists principally of sand dunes. There is no natural harbour, but traces of ruins near the shore mark the site of the old Maiuma Gazae or Port of Gaza, now called el Mineh, which in the 5th century was a separate town and episcopal see, under the title Constantia or Limena Gaza. Hashem, an ancestor of Mahomet, lies buried in the town. On the east are remains of a race-course, the corners marked by granite shafts with Greek inscriptions on them. To the south is a remarkable hill, quite isolated and bare, with a small mosque and a graveyard. It is called el Muntar, "the watch tower," and is supposed to be the mountain "before (or facing) Hebron," to which Samson carried the gates of Gaza (Judg. xvi. 3). The bazaars of Gaza are considered good. An extensive pottery exists in the town, and black earthenware peculiar to the place is manufactured there. The climate is dry and comparatively healthy, but the summer temperature often exceeds 110° Fahr. The surrounding country is partly cornland, partly waste, and is inhabited by wandering Arabs. The prosperity of Ghuzzeh has partially revived through the growing trade in barley, of which the average annual export to Great Britain for 1897-1899 was over 30,000 tons. The dress of the people is Egyptian rather than Syrian. Gaza is an episcopal see both of the Greek and the Armenian church. The Church Missionary Society maintains a mission, with schools for both sexes, and a hospital.

GAZALAND, a district of Portuguese East Africa, extending north from the Komati or Manhissa river, Delagoa Bay, to the Pungwe river. It is a well-watered, fertile country. Gazaland is one of the chief recruiting grounds for negro labour in the Transvaal gold mines. The country derives its name from a Swazi chief named Gaza, a contemporary of Chaka, the Zulu king. Refugees from various clans oppressed by Dingaan (Chaka's successor) were welded into one tribe by Gaza's son Manikusa, who took the name of Sotshangana, his followers being known generally as Matshangana. A section of them was called Maviti or Landeens (i.e. couriers), a designation which persists as a tribal name. Between 1833 and 1836 Manikusa made himself master of the country as far north as the Zambezi and captured the Portuguese posts at Delagoa Bay, Inhambane, Sofala and Sena, killing nearly all the inhabitants. The Portuguese reoccupied their posts, but held them with great difficulty, while in the interior the Matshangana continued their ravages unchecked, depopulating large regions. Manikusa died about 1860, and his son Umzila, receiving some help from the Portuguese at Delagoa Bay in a struggle against a brother for the chieftainship, ceded to them the territory south of the Manhissa river. North of that stream as far as the Zambezi and inland to the continental plateau Umzila established himself in independence, a position he maintained till his death (c. 1884). His chief rival was a Goanese named Gouveia, who came to Africa about 1850. Having obtained possession of a _prazo_ in the Gorongoza district, he ruled there as a feudal lord while acknowledging himself a Portuguese subject. Gouveia recovered from the Matshangana and other troublers of the peace much of the country in the Zambezi valley, and was appointed by the Portuguese captain-general of a large region. From 1868 onward the country began to be better known. Probably the first European to penetrate any distance inland from the Sofala coast since the Portuguese gold-seekers of the 16th century was St Vincent W. Erskine, who explored the region between the Limpopo and Pungwe (1868-1875). Portugal's hold on the coast had been more firmly established at the time of Umzila's death, and Gungunyana, his successor, was claimed as a vassal, while efforts were made to open up the interior. This led in 1890-1891 to collisions on the borderland of the plateau with the newly established British South Africa Company, and to the arrest by the company's agents of Gouveia, who was, however, set at liberty and returned to Mozambique via Cape Town. An offer made by Gungunyana (1891) to come under British protection was not accepted. In 1892 Gouveia was killed in a war with a native chief. Gungunyana maintained his independence until 1895, when he was captured by a Portuguese force and exiled, first to Lisbon and afterwards to Angola, where he died in 1906. With the capture of Gungunyana opposition to Portuguese rule largely ceased.

In flora, fauna and commerce Gazaland resembles the neighbouring regions of Portuguese East Africa. (q.v.).

See G. McCall Theal, _History of South Africa since 1795_, vol. v. (London, 1908).

GAZEBO (usually explained as a comic Latinism, for "I will gaze"; the _New English Dictionary_ suggests a possible oriental origin now lost), a term used in the 18th century for a structure on the outer wall of a garden, having an upper storey with windows on each side so as to overlook the road. Similar buildings are found in Holland on the borders of the canals, which in some cases form very picturesque features.

GAZETTE, a name given to news-sheets or newspapers having an abstract of current events (see NEWSPAPERS). The _London Gazette_ is the title of the English official organ for announcements by the government, and is published every Tuesday and Friday. It contains all proclamations, orders of council, promotions and appointments to commissions in the army and navy, all appointments to offices of state, and such other orders, rules and regulations as are directed by act of parliament to be published therein. It also contains notices of proceedings in bankruptcy, dissolutions of partnership, &c. By the Documentary Evidence