CHAPTER VI

LINNÆUS AND SCIENTIFIC NATURAL HISTORY

We turn now from the purely anatomical side to consider the parallel development of the classification of animals and of plants. Descriptive natural history reached a very low level in the early Christian centuries, and remained there throughout the Middle Ages. The return to the writings of Aristotle was the first influence tending to lift it to the position from which it had fallen. After the decline of ancient civilization there was a period in which the writers of classical antiquity were not read. Not only were the writings of the ancient philosophers neglected, but so also were those of the literary men as well, the poets, the story-tellers, and the historians. As related in Chapter I, there were no observations of animated nature, and the growing tendency of the educated classes to envelop themselves in metaphysical speculations was a feature of intellectual life.

The Physiologus or Sacred Natural History.--During this period of crude fancy, with a fog of mysticism obscuring all phenomena of nature, there existed a peculiar kind of natural history that was produced under theological influence. The manuscripts in which this sacred natural history was embodied exist in various forms and in about a dozen languages of Eastern and Western Europe. The writings are known under the general title of the Physiologus, or the Bestiarius. This served for nearly a thousand years as the principal source of thought regarding natural history. It contains accounts of animals mentioned in the Bible and others of a purely mythical character. These are made to be symbolical of religious beliefs, and are often accompanied by quotations of texts and by moral reflections. The phoenix rising from its ashes typifies the resurrection of Christ. In reference to young lions, the _Physiologus_ says: "The lioness giveth birth to cubs which remain three days without life. Then cometh the lion, breatheth upon them, and bringeth them to life.... Thus it is that Jesus Christ during three days was deprived of life, but God the Father raised him gloriously." (Quoted from White, p. 35.) Besides forty or fifty common animals, the unicorn and the dragon of the Scriptures, and the fabled basilisk and phoenix of secular writings are described, and morals are drawn from the stories about them. Some of the accounts of animals, as the lion, the panther, the serpent, the weasel, etc., etc., are so curious that, if space permitted, it would be interesting to quote them; but that would keep us too long from following the rise of scientific natural history from this basis.

For a long time the religious character of the contemplations of nature was emphasized and the prevalence of theological influence in natural history is shown in various titles, as Lesser's _Theology of Insects_, Swammerdam's _Biblia Naturæ_, Spallanzani's _Tracts_, etc.

The zoölogy of the _Physiologus_ was of a much lower grade than any we know about among the ancients, and it is a curious fact that progress was made by returning to the natural history of fifteen centuries in the past. The translation of Aristotle's writings upon animals, and the disposition to read them, mark this advance. When, in the Middle Ages, the boundaries of interest began to be extended, it came like an entirely new discovery, to find in the writings of the ancients a storehouse of philosophic thought and a higher grade of learning than that of the period. The translation and recopying of the writers of classical antiquity was, therefore, an important step in the revival of learning. These writings were so much above the thought of the time that the belief was naturally created that the ancients had digested all learning, and they were pointed to as unfailing authorities in matters of science.

The Return to the Science of the Ancients.--The return to Aristotle was wholesome, and under its influence men turned their attention once more to real animals. Comments upon Aristotle began to be made, and in course of time independent treatises upon animals began to appear. One of the first to modify Aristotle to any purpose was Edward Wotton, the English physician, who published in 1552 a book on the distinguishing characteristics of animals (_De Differentiis Animalium_). This was a complete treatise on the zoölogy of the period, including an account of the different races of mankind. It was beautifully printed in Paris, and was dedicated to Edward VI. Although embracing ten books, it was by no means so ponderous as were some of the treatises that followed it. The work was based upon Aristotle, but the author introduced new matter, and also added the group of zoöphytes, or plant-like animals of the sea.

Gesner.--The next to reach a distinctly higher plane was Conrad Gesner (1516-1565), the Swiss, who was a contemporary of Vesalius. He was a practising physician who, in 1553, was made professor of natural history in Zurich. A man of extraordinary talent and learning, he turned out an astonishing quantity of work. Besides accomplishing much in scientific lines, he translated from Greek, Arabic, and Hebrew, and published in twenty volumes a universal catalogue of all works known in Latin, Greek, and Hebrew, either printed or in manuscript form. In the domain of natural history he began to look critically at animals with a view to describing them, and to collect with zealous care new observations upon their habits. His great work on natural history (_Historia Animalium_) began to appear in 1551, when he was thirty-five years of age, and four of the five volumes were published by 1556. The fifth volume was not published until 1587, twenty-two years after his death. The complete work consists of about "4,500 folio pages," profusely illustrated with good figures. The edition which the writer has before him--that of 1585-1604--embraces 3,200 pages of text and 953 figures.

Brooks says: "One of Gesner's greatest services to natural science is the introduction of good illustrations, which he gives his reader by hundreds." He was so exacting about the quality of his illustrations that his critical supervision of the work of artists and engravers had its influence upon contemporary art. Some of the best woodcuts of the period are found in his work. His friend Albrecht Dürer supplied one of the originals--the drawing of the rhinoceros--and it is interesting to note that it is by no means the best, a circumstance which indicates how effectively Gesner held his engraver and draughtsman up to fine work. He was also careful to mold his writing into graceful form, and this, combined with the illustrations, "made science attractive without sacrificing its dignity, and thus became a great educational influence."

In preparing his work he sifted the writings of about two hundred and fifty authors, and while his book is largely a compilation, it is enriched with many observations of his own. His descriptions are verbose, but discriminating in separating facts and observations from fables and speculations. He could not entirely escape from old traditions. There are retained in his book pictures of the sea-serpent, the mermaids, and a few other fanciful and grotesque sketches, but for the most part the drawings are made from the natural objects. The descriptions are in several parts of his work alphabetically arranged, for convenience of reference, and thus animals that were closely related are often widely separated.

Gesner (Fig. 32) sacrificed his life to professional zeal during the prevalence of the plague in Zurich in 1564. Having greatly overworked in the care of the sick, he was seized with the disease, and died at the age of forty-nine.

Considered from the standpoint of descriptions and illustrations, Gesner's _Historia Animalium_ remained for a long time the best work in zoölogy. He was the best zoölogist between Aristotle and John Ray, the immediate predecessor of Linnæus.

Jonston and Aldrovandi.--At about the same period as Gesner's work there appeared two other voluminous publications, which are well known--those of Jonston, the Scot (_Historia Animalium_, 1549-1553), and Aldrovandi, the Italian (_Opera_, 1599-1606). The former consisted of four folio volumes, and the latter of thirteen, of ponderous size, to which was added a fourteenth on plants. Jonston's works were translated, and were better known in England than those of Gesner and Aldrovandi. The wood-engravings in Aldrovandi's volume are coarser than those of Gesner, and are by no means so lifelike. In the Institute at Bologna are preserved twenty volumes of figures of animals in color, which were the originals from which the engravings were made. These are said to be much superior to the reproductions. The encyclopædic nature of the writings of Gesner, Aldrovandi, and Jonston has given rise to the convenient and expressive title of the encyclopædists.

Ray.--John Ray, the forerunner of Linnæus, built upon the foundations of Gesner and others, and raised the natural-history edifice a tier higher. He greatly reduced the bulk of publications on natural history, sifting from Gesner and Aldrovandi their irrelevancies, and thereby giving a more modern tone to scientific writings. He was the son of a blacksmith, and was born in southern England in 1628. The original form of the family name was Wray. He was graduated at the University of Cambridge, and became a fellow of Trinity College. Here he formed a friendship with Francis Willughby, a young man of wealth whose tastes for natural history were like his own. This association proved a happy one for both parties. Ray had taken orders in the Church of England, and held his university position as a cleric; but, from conscientious scruples, he resigned his fellowship in 1662. Thereafter he received financial assistance from Willughby, and the two men traveled extensively in Great Britain and on the Continent, with the view of investigating the natural history of the places that they visited. On these excursions Willughby gave particular attention to animals and Ray to plants. Of Ray's several publications in botany, his _Historia Plantarum_ in three volumes (1686-1704) is the most extensive. In another work, as early as 1682, he had proposed a new classification of plants, which in the next century was adopted by Jussieu, and which gives Ray a place in the history of botany.

Willughby died in 1662, at the age of thirty-eight, leaving an annuity to Ray, and charging him with the education of his two sons, and the editing of his manuscripts. Ray performed these duties as a faithful friend and in a generous spirit. He edited and published Willughby's book on birds (1678) and fishes (1686) with important additions of his own, for which he sought no credit.

After completing his tasks as the literary executor of Willughby, he returned in 1678 to his birthplace and continued his studies in natural history. In 1691 he published "The Wisdom of God manifested in the Works of the Creation," which was often reprinted, and became the forerunner of the works on natural theology like Paley's, etc. This was an amplification of ideas he had embodied in a sermon thirty-one years earlier, and which at that time attracted much notice. He now devoted himself largely to the study of animals, and in 1693 published a work on the quadrupeds and serpents, a work which gave him high rank in the history of the classification of animals. He died in 1705, but he had accomplished much good work, and was not forgotten. In 1844 there was founded, in London, in his memory, the Ray Society for the publication of rare books on botany and zoölogy.

Ray's Idea of Species.--One of the features of Ray's work, in the light of subsequent development, is of special interest, and that is his limiting of species. He was the first to introduce into natural history an exact conception of species. Before his time the word had been used in an indefinite sense to embrace groups of greater or less extent, but Ray applied it to individuals derived from similar parents, thus making the term species stand for a particular kind of animal or plant. He noted some variations among species, and did not assign to them that unvarying and constant character ascribed to them by Linnæus and his followers. Ray also made use of anatomy as the foundation for zoölogical classification, and introduced great precision and clearness into his definitions of groups of animals and plants. In the particulars indicated above he represents a great advance beyond any of his precursors, and marks the parting of the ways between mediæval and modern natural history.

In Germany Klein (1685-1759) elaborated a system of classification embracing the entire animal kingdom. His studies were numerous, and his system would have been of much wider influence in molding natural history had it not been overshadowed by that of Linnæus.

Linnæus or Linné.--The service of Linnæus to natural history was unique. The large number of specimens of animals and plants, ever increasing through the collections of travelers and naturalists, were in a confused state, and there was great ambiguity arising from the lack of a methodical way of arranging and naming them. They were known by verbose descriptions and local names. No scheme had as yet been devised for securing uniformity in applying names to them. The same animal and plant had different names in the different sections of a country, and often different plants and animals had the same name. In different countries, also, their names were greatly diversified. What was especially needed was some great organizing mind to catalogue the animals and plants in a systematic way, and to give to natural science a common language. Linnæus possessed this methodizing mind and supplied the need. While he did little to deepen the knowledge of the organization of animal and plant life, he did much to extend the number of known forms; he simplified the problem of cataloguing them, and he invented a simple method of naming them which was adopted throughout the world. By a happy stroke he gave to biology a new language that remains in use to-day. The tremendous influence of this may be realized when we remember that naturalists everywhere use identical names for the same animals and plants. The residents of Japan, of Italy, of Spain, of all the world, in fact, as was just said, employ the same Latin names in classifying organic forms.

He also inspired many students with a love for natural history and gave an impulse to the advance of that science which was long felt. We can not gainsay that a higher class of service has been rendered by those of philosophic mind devoted to the pursuit of comparative anatomy, but the step of Linnæus was a necessary one, and aided greatly in the progress of natural history. Without this step the discoveries and observations of others would not have been so readily understood, and had it not been for his organizing force all natural science would have been held back for want of a common language. A close scrutiny of the practice among naturalists in the time of Linnæus shows that he did not actually invent the binomial nomenclature, but by adopting the suggestions of others he elaborated the system of classification and brought the new language into common use.

Personal History.--Leaving for the present the system of Linnæus, we shall give attention to the personal history of the man. The great Swedish naturalist was born in Rashult in 1707. His father was the pastor of the village, and intended his eldest son, Carl, for the same high calling. The original family name was Ignomarsen, but it had been changed to Lindelius, from a tall linden-tree growing in that part of the country. In 1761 a patent of nobility was granted by the crown to Linnæus, and thereafter he was styled Carl von Linné.

His father's resources were very limited, but he managed to send his son to school, though it must be confessed that young Linnæus showed little liking for the ordinary branches of instruction. His time was spent in collecting natural-history specimens, and his mind was engaged in thinking about them. The reports of his low scholarship and the statement of one of his teachers that he showed no aptitude for learning were so disappointing to his father that, in 1726, he prepared to apprentice Carl to a shoemaker, but was prevented from doing so through the encouragement of a doctor who, being able to appreciate the quality of mind possessed by the young Linnæus, advised allowing him to study medicine instead of preparing for theology.

Accordingly, with a sum amounting to about $40, all his father could spare, he set off for the University of Lund, to pursue the study of medicine. He soon transferred to the University of Upsala, where the advantages were greater. His poverty placed him under the greatest straits for the necessities of life, and he enjoyed no luxuries. While in the university he mended his shoes, and the shoes which were given to him by some of his companions, with paper and birch-bark, to keep his feet from the damp earth. But his means did not permit of his taking his degree at Upsala, and it was not until eight years later, in 1735, that he received his degree in Holland.

At Upsala he was relieved from his extreme poverty by obtaining an assistant's position, and so great was his knowledge of plants that he was delegated to read the lectures of the aged professor of botany, Rudbeck.

In 1732 he was chosen by the Royal Society of Upsala to visit Lapland as a collector and observer, and left the university without his degree. On returning to Upsala, his lack of funds made itself again painfully felt, and he undertook to support himself by giving public lectures on botany, chemistry, and mineralogy. He secured hearers, but the continuance of his lectures was prevented by one of his rivals on the ground that Linnæus had no degree, and was therefore legally disqualified from taking pay for instruction. Presently he became tutor and traveling companion of a wealthy baron, the governor of the province of Dalecarlia, but this employment was temporary.

Helped by His Fiancée.--His friends advised him to secure his medical degree and settle as a practitioner. Although he lacked the necessary funds, one circumstance contributed to bring about this end: he had formed an attachment for the daughter of a wealthy physician, named Moré or Moræus, and on applying for her hand in marriage, her father made it a condition of his consent that Linnæus should take his medical degree and establish himself in the practice of medicine. The young lady, who was thrifty as well as handsome, offered her savings, amounting to one hundred dollars (Swedish), to her lover. He succeeded in adding to this sum by his own exertions, and with thirty-six Swedish ducats set off for Holland to qualify for his degree. He had practically met the requirements for the medical degree by his previous studies, and after a month's residence at the University of Hardewyk, his thesis was accepted and he was granted the degree in June, 1735, in the twenty-eighth year of his age.

Instead of returning at once to Sweden, he went to Leyden, and made the acquaintance of several well-known scientific men. He continued his botanical studies with great energy, and now began to reap the benefits of his earlier devotion to natural history. His heart-breaking and harassing struggles were now over.

The Systema Naturæ.--He had in his possession the manuscript of his _Systema Naturæ_, and with the encouragement of his new friends it was published in the same year. The first edition (1735) of that notable work, which was afterward to bring him so much fame, consisted of twelve printed folio pages. It was merely an outline of the arrangements of plants, animals, and minerals in a methodical catalogue. This work passed through twelve editions during his lifetime, the last one appearing in 1768. After the first edition, the books were printed in octavo form, and in the later editions were greatly enlarged. A copy of the first edition was sent to Boerhaave, the most distinguished professor in the University of Leyden, and secured for Linnæus an interview with that distinguished physician, who treated him with consideration and encouraged him in his work. Boerhaave was already old, and had not long to live; and when Linnæus was about to leave Holland in 1738, he admitted him to his sick-chamber and bade him a most affectionate adieu, and encouraged him to further work by most kindly and appreciative expressions.

Through the influence of Boerhaave, Linnæus became the medical attendant of Cliffort, the burgomaster at Amsterdam, who had a large botanic garden. Cliffort, being desirous of extending his collections, sent Linnæus to England, where he met Sir Hans Sloane and other eminent scientific men of Great Britain. After a short period he returned to Holland, and in 1737 brought out the _Genera Plantarum_, a very original work, containing an analysis of all the genera of plants. He had previously published, besides the _Systema Naturæ_, his _Fundamenta Botanica_, 1735, and _Bibliotheca Botanica_, 1736, and these works served to spread his fame as a botanist throughout Europe.

His Wide Recognition.--An illustration of his wide recognition is afforded by an anecdote of his first visit to Paris in 1738. "On his arrival he went first to the Garden of Plants, where Bernard de Jussieu was describing some exotics in Latin. He entered without opportunity to introduce himself. There was one plant which the demonstrator had not yet determined, and which seemed to puzzle him. The Swede looked on in silence, but observing the hesitation of the learned professor, cried out '_Hæc planta faciem Americanam habet_.' 'It has the appearance of an American plant.' Jussieu, surprised, turned about quickly and exclaimed 'You are Linnæus.' 'I am, sir,' was the reply. The lecture was stopped, and Bernard gave the learned stranger an affectionate welcome."

Return to Sweden.--After an absence of three and one-half years, Linnæus returned to his native country in 1738, and soon after was married to the young woman who had assisted him and had waited for him so loyally. He settled in Stockholm and began the practice of medicine. In the period of his absence he had accomplished much: visited Holland, England, and France, formed the acquaintance of many eminent naturalists, obtained his medical degree, published numerous works on botany, and extended his fame over all Europe. In Stockholm, however, he was for a time neglected, and he would have left his native country in disgust had it not been for the dissuasion of his wife.

Professor in Upsala.--In 1741 he was elected professor of anatomy in the University of Upsala, but by a happy stroke was able to exchange that position for the professorship of botany, materia medica, and natural history that had fallen to his former rival, Rosen. Linnæus was now in his proper element; he had opportunity to lecture on those subjects to which he had been devotedly attached all his life, and he entered upon the work with enthusiasm.

He attracted numerous students by the power of his personal qualities and the excellence of his lectures. He became the most popular professor in the University of Upsala, and, owing to his drawing power, the attendance at the university was greatly increased. In 1749 he had 140 students devoted to studies in natural history. The number of students at the university had been about 500; "whilst he occupied the chair of botany there it rose to 1,500." A part of this increase was due to other causes, but Linnæus was the greatest single drawing force in the university. He was an eloquent as well as an enthusiastic lecturer, and he aroused great interest among his students, and he gave an astonishing impulse to the study of natural history in general, and to botany in particular. Thus Linnæus, after having passed through great privations in his earlier years, found himself, at the age of thirty-four, established in a position which brought him recognition, honor, and large emolument.

In May, 1907, the University of Upsala celebrated the two hundredth anniversary of his birth with appropriate ceremonies. Delegations of scientific men from all over the world were in attendance to do honor to the memory of the great founder of biological nomenclature.

Personal Appearance.--The portrait of Linnæus at the age of sixty is shown in Fig. 34. He was described as of "medium height, with large limbs, brown, piercing eyes, and acute vision." His hair in early youth was nearly white, and changed in his manhood to brown, and became gray with the advance of age. Although quick-tempered, he was naturally of a kindly disposition, and secured the affection of his students, with whom he associated and worked in the most informal way. His love of approbation was very marked, and he was so much praised that his desire for fame became his dominant passion. The criticism to which his work was subjected from time to time accordingly threw him into fits of despondency and rage.

His Influence upon Natural History.--However much we may admire the industry and force of Linnæus, we must admit that he gave to natural history a one-sided development, in which the more essential parts of the science received scant recognition. His students, like their master, were mainly collectors and classifiers. "In their zeal for naming and classifying, the higher goal of investigation, knowledge of the nature of animals and plants, was lost sight of and the interest in anatomy, physiology, and embryology lagged."

R. Hertwig says of him: "For while he in his _Systema Naturæ_ treated of an extraordinarily larger number of animals than any earlier naturalist, he brought about no deepening of our knowledge. The manner in which he divided the animal kingdom, in comparison with the Aristotelian system, is to be called rather a retrogression than an advance. Linnæus divided the animal kingdom into six classes--Mammalia, Aves, Amphibia, Pisces, Insecta, Vermes. The first four classes correspond to Aristotle's four groups of animals with blood. In the division of the invertebrated animals into Insecta and Vermes Linnæus stands undoubtedly behind Aristotle, who attempted, and in part indeed successfully, to set up a larger number of groups.

"But in his successors even more than in Linnæus himself we see the damage wrought by the purely systematic method of consideration. The diagnoses of Linnæus were for the most part models, which, _mutatis mutandis_, could be employed for new species with little trouble. There was needed only some exchanging of adjectives to express the differences. With the hundreds of thousands of different species of animals, there was no lack of material, and so the arena was opened for that spiritless zoölogy of species-making, which in the first half of the nineteenth century brought zoölogy into such discredit. Zoölogy would have been in danger of growing into a Tower of Babel of species-description if a counterpoise had not been created in the strengthening of the physiologico-anatomical method of consideration."

His Especial Service.--Nevertheless, the work of Linnæus made a lasting impression upon natural history, and we shall do well to get clearly in mind the nature of his particular service. In the first place, he brought into use the method of naming animals and plants which is employed to-day. In his _Systema Naturæ_ and in other publications he employed a means of naming every natural production in two words, and it is therefore called the binomial nomenclature. An illustration will make this clearer. Those animals which had close resemblance, like the lion, tiger, leopard, the lynx, and the cat, he united under the common generic name of _Felis_, and gave to each a particular trivial name, or specific name. Thus the name of the lion became _Felis leo_, of the tiger _Felis tigris_, of the leopard _Felis pardus_, of the cat Felis catus; and to these the modern zoölogists have added, making the Canada lynx _Felis Canadensis_, the domestic cat _Felis domesticata_, etc. In a similar way, the dog-like animals were united into a genus designated _Canis_, and the particular kinds or species became _Canis lupus_, the wolf, _Canis vulpes_, the fox, _Canis familiaris_, the common dog. This simple method took the place of the varying names applied to the same animal in different countries and local names in the same country. It recognized at once their generic likeness and their specific individuality.

All animals, plants, and minerals were named according to this method. Thus there were introduced into nomenclature two groups, the genus and the species. The name of the genus was a noun, and that of the species an adjective agreeing with it. In the choice of these names Linnæus sought to express some distinguishing feature that would be suggestive of the particular animal, plant, or mineral. The trivial, or specific, names were first employed by Linnæus in 1749, and were introduced into his _Species Plantarum_ in 1753, and into the tenth edition of his _Systema Naturæ_ in 1758.

We recognize Linnæus as the founder of nomenclature in natural history, and by the common consent of naturalists the date 1758 has come to be accepted as the starting-point for determining the generic and specific names of animals. The much vexed question of priority of names for animals is settled by going back to the tenth edition of his _Systema Naturæ_, while the botanists have adopted his _Species Plantarum_, 1753, as their base-line for names. As to his larger divisions of animals and plants, he recognized classes and orders. Then came genera and species. Linnæus did not use the term family in his formulæ; this convenient designation was first used and introduced in 1780 by Batch.

The _Systema Naturæ_ is not a treatise on the organization of animals and plants; it is rather a catalogue of the productions of nature methodically arranged. His aim in fact was not to give full descriptions, but to make a methodical arrangement.

To do justice, however, to the discernment of Linnæus, it should be added that he was fully aware of the artificial nature of his classification. As Kerner has said: "It is not the fault of this accomplished and renowned naturalist if a greater importance were attached to his system than he himself ever intended. Linnæus never regarded his twenty-four classes as real and natural divisions of the vegetable kingdom, and specifically says so; it was constructed for convenience of reference and identification of species. A real natural system, founded on the true affinities of plants as indicated by the structural characters, he regarded as the highest aim of botanical endeavor. He never completed a natural system, leaving only a fragment (published in 1738)."

Terseness of Descriptions.--His descriptions were marked by extreme brevity, but by great clearness. This is a second feature of his work. In giving the diagnosis of a form he was very terse. He did not employ fully formed sentences containing a verb, but words concisely put together so as to bring out the chief things he wished to emphasize. As an illustration of this, we may take his characterization of the forest rose, "_Rosa sylvestris vulgaris, flore odorata incarnato_." The common rose of the forest with a flesh-colored, sweet-smelling flower. In thus fixing the attention upon essential points he got rid of verbiage, a step that was of very great importance.

His Idea of Species.--A third feature of his work was that of emphasizing the idea of species. In this he built upon the work of Ray. We have already seen that Ray was the first to define species and to bring the conception into natural history. Ray had spoken of the variability of species, but Linnæus, in his earlier publications, declared that they were constant and invariable. His conception of a species was that of individuals born from similar parents. It was assumed that at the original stocking of the earth, one pair of each kind of animals was created, and that existing species were the direct descendants without change of form or habit from the original pair. As to their number, he said: "_Species tot sunt, quot formæ ab initio creatæ sunt_"--there are just so many species as there were forms created in the beginning; and his oft-quoted remark, "_Nulla species nova_," indicates in terse language his position as to the formation of new species. Linnæus took up this idea as expressing the current thought, without analysis of what was involved in it. He readily might have seen that if there were but a single pair of each kind, some of them must have been sacrificed to the hunger of the carnivorous kinds: but, better than making any theories, he might have looked for evidence in nature as to the fixity of species.

While Linnæus first pronounced upon the fixity of species, it is interesting to note that his extended observations upon nature led him to see that variation among animals and plants is common and extensive, and accordingly in the later editions of his _Systema Naturæ_ we find him receding from the position that species are fixed and constant. Nevertheless, it was owing to his influence, more than to that of any other writer of the period, that the dogma of fixity of species was established. His great contemporary Buffon looked upon species as not having a fixed reality in nature, but as being figments of the imagination; and we shall see in a later section of this book how the idea of Linnæus in reference to the fixity of species gave way to accumulating evidence on the matter.

Summary.--The chief services of Linnæus to natural science consisted of these three things: bringing into current use the binomial nomenclature, the introduction of terse formulæ for description, and fixing attention upon species. The first two were necessary steps; they introduced clearness and order into the management of the immense number of details, and they made it possible for the observations and discoveries of others to be understood and to take their place in the great system of which he was the originator. The effect of the last step was to direct the attention of naturalists to species, and thereby to pave the way for the coming consideration of their origin, a consideration which became such a burning question in the last half of the nineteenth century.

Reform of the Linnæan System

Necessity of Reform.--As indicated above, the classification established by Linnæus had grave defects; it was not founded on a knowledge of the comparative structure of animals and plants, but in many instances upon superficial features that were not distinctive in determining their position and relationships. His system was essentially an artificial one, a convenient key for finding the names of animals and plants, but doing violence to the natural arrangement of those organisms. An illustration of this is seen in his classification of plants into classes, mainly on the basis of the number of stamens in the flower, and into orders according to the number of pistils. Moreover, the true object of investigation was obscured by the Linnæan system. The chief aim of biological study being to extend our knowledge of the structure, development, and physiology of animals and plants as a means of understanding more about their life, the arrangement of animals and plants into groups should be the outcome of such studies rather than an end in itself.

It was necessary to follow different methods to bring natural history back into the line of true progress. The first modification of importance to the Linnæan system was that of Cuvier, who proposed a grouping of animals based upon a knowledge of their comparative anatomy. He declared that animals exhibit four types of organization, and his types were substituted for the primary groups of Linnæus.

The Scale of Being.--In order to understand the bearing of Cuvier's conclusions we must take note of certain views regarding the animal kingdom that were generally accepted at the time of his writing. Between Linnæus and Cuvier there had emerged the idea that all animals, from the lowest to the highest, form a graduated series. This grouping of animals into a linear arrangement was called exposing the Scale of Being, or the Scale of Nature (_Scala Naturæ_). Buffon, Lamarck, and Bonnet were among the chief exponents of this idea.

That Lamarck's connection with it was temporary has been generally overlooked. It is the usual statement in the histories of natural science, as in the _Encyclopædia Britannica_, in the History of Carus, and in Thomson's _Science of Life_, that the idea of the scale of nature found its fullest expression in Lamarck. Thomson says: "His classification (1801-1812) represents the climax of the attempt to arrange the groups of animals in linear order from lower to higher, in what was called a _scala naturæ_" (p. 14). Even so careful a writer as Richard Hertwig has expressed the matter in a similar form. Now, while Lamarck at first adopted a linear classification, it is only a partial reading of his works that will support the conclusion that he held to it. In his _Système des Animaux sans Vertèbres_, published in 1801, he arranged animals in this way; but to do credit to his discernment, it should be observed that he was the first to employ a genealogical tree and to break up the serial arrangement of animal forms. In 1809, in the second volume of his _Philosophie Zoologique_, as Packard has pointed out, he arranged animals according to their relationships, in the form of a trunk with divergent branches. This was no vague suggestion on his part, but an actual pictorial representation of the relationship between different groups of animals, as conceived by him. Although a crude attempt, it is interesting as being the first of its kind. This is so directly opposed to the idea of scale of being that we make note of the fact that Lamarck forsook that view at least twenty years before the close of his life and substituted for it that of the genealogical tree.

Lamarck's Position in Science.--Lamarck is coming into full recognition for his part in founding the evolution theory, but he is not generally, as yet, given due credit for his work in zoölogy. He was the most philosophical thinker engaged with zoölogy at the close of the eighteenth and the beginning of the nineteenth century. He was greater than Cuvier in his reach of intellect and in his discernment of the true relationships among living organisms. We are to recollect that he forsook the dogma of fixity of species, to which Cuvier held, and founded the first comprehensive theory of organic evolution. To-day we can recognize the superiority of his mental grasp over that of Cuvier, but, owing to the personal magnetism of the latter and to his position, the ideas of Lamarck, which Cuvier combated, received but little attention when they were promulgated. We shall have occasion in a later chapter to speak more fully of Lamarck's contribution to the progress of biological thought.

Cuvier's Four Branches.--We now return to the type-theory of Cuvier. By extended studies in comparative anatomy, he came to the conclusion that animals are constructed upon four distinct plans or types: the vertebrate type; the molluscan type; the articulated type, embracing animals with joints or segments; and the radiated type, the latter with a radial arrangement of parts, like the starfish; etc. These types are distinct, but their representatives, instead of forming a linear series, overlap so that the lowest forms of one of the higher groups are simpler in organization than the higher forms of a lower group. This was very illuminating, and, being founded upon an analysis of structure, was important. It was directly at variance with the idea of scale of being, and overthrew that doctrine.

Cuvier first expressed these views in a pamphlet published in 1795, and later in a better-known paper read before the French Academy in 1812, but for the full development of his type-theory we look to his great volume on the animal kingdom published in 1816. The central idea of his arrangement is contained in the secondary title of his book, "The Animal Kingdom Arranged According to its Organization" (_Le Règne Animal Distribué d'après son Organisation_, 1816). The expression "arranged according to its organization" embraces the feature in which this analysis of animals differs from all previous attempts.

Correlation of Parts.--An important idea, first clearly expressed by Cuvier, was that of correlation of parts. The view that the different parts of an animal are so correlated that a change in one, brought about through changes in use, involves a change in another. For illustration, the cleft hoof is always associated with certain forms of teeth and with the stomach of a ruminant. The sharp claws of flesh-eating animals are associated with sharp, cutting teeth for tearing the flesh of the victims, and with an alimentary tube adapted to the digestion of a fleshy diet. Further account of Cuvier is reserved for the chapter on the Rise of Comparative Anatomy, of which he was the founder.

Von Baer.--The next notable advance affecting natural history came through the work of Von Baer, who, in 1828, founded the science of development of animal forms. He arrived at substantially the same conclusions as Cuvier. Thus the system founded upon comparative anatomy by Cuvier came to have the support of Von Baer's studies in embryology.

The contributions of these men proved to be a turning-point in natural history, and subsequent progress in systematic botany and zoölogy resulted from the application of the methods of Cuvier and Von Baer, rather than from following that of Linnæus. His nomenclature remained a permanent contribution of value, but the knowledge of the nature of living forms has been advanced chiefly by studies in comparative anatomy and embryology, and, also, in the application of experiments.

The most significant advances in reference to the classification of animals was to come as a result of the acceptance of the doctrine of organic evolution, subsequent to 1859. Then the relationships between animals were made to depend upon community of descent, and a distinction was drawn between superficial or apparent relationships and those deep-seated characteristics that depend upon close genetic affinities.

Alterations by Von Siebold and Leuckart.--But, in the mean time, naturalists were not long in discovering that the primary divisions established by Cuvier were not well balanced, and, indeed, that they were not natural divisions of the animal kingdom. The group Radiata was the least sharply defined, since Cuvier had included in it not only those animals which exhibit a radial arrangement of parts, but also unicellular organisms that were asymmetrical, and some of the worms that showed bilateral symmetry. Accordingly, Karl Th. von Siebold, in 1845, separated these animals and redistributed them. For the simplest unicellular animals he adopted the name Protozoa, which they still retain, and the truly radiated forms, as starfish, sea-urchins, hydroid polyps, coral animals, etc., were united in the group Zoöphyta. Von Siebold also changed Cuvier's branch, Articulata, separating those forms as crustacea, insects, spiders, and myriopods, which have jointed appendages, into a natural group called Arthropoda, and uniting the segmented worms with those worms that Cuvier has included in the radiate group, into another branch called Vermes. This separation of the four original branches of Cuvier was a movement in the right direction, and was destined to be carried still farther.

Von Siebold (Fig. 35) was an important man in the progress of zoölogy, especially in reference to the comparative anatomy of the invertebrates.

Leuckart (Fig. 36), whose fame as a lecturer and teacher attracted many young men to the University of Leipsic, is another conspicuous personality in zoölogical progress.

This distinguished zoölogist, following the lead of Von Siebold, made further modifications. He split Von Siebold's group of Zoöphytes into two distinct kinds of radiated animals; the star-fishes, sea-urchins, sea-cucumbers, etc., having a spiny skin, he designated Echinoderma; the jelly-fishes, polyps, coral animals, etc., not possessing a true body cavity, were also united into a natural group, for which he proposed the name Coelenterata.

From all these changes there resulted the seven primary divisions--branches, subkingdoms, or phyla--which, with small modifications, are still in use. These are Protozoa, Coelenterata, Echinoderma, Vermes, Arthropoda, Mollusca, Vertebrata. These seven phyla are not entirely satisfactory, and there is being carried on a redistribution of forms, as in the case of the brachiopods, the sponges, the tunicates, etc. While all this makes toward progress, the changes are of more narrow compass than those alterations due to Von Siebold and Leuckart.

Summary.--In reviewing the rise of scientific natural history, we observe a steady development from the time of the _Physiologus_, first through a return to Aristotle, and through gradual additions to his observations, notably by Gesner, and then the striking improvements due to Ray and Linnæus. We may speak of the latter two as the founders of systematic botany and zoölogy. But the system left by Linnæus was artificial, and the greatest obvious need was to convert it into a natural system founded upon a knowledge of the structure and the development of living organisms. This was begun by Cuvier and Von Baer, and was continued especially by Von Siebold and Leuckart. To this has been added the study of habits, breeding, and adaptations of organisms, a study which has given to natural history much greater importance than if it stood merely for the systematic classification of animals and plants.

Tabular View of Classifications.--A table showing the primary groups of Linnæus, Cuvier, Von Siebold, and Leuckart will be helpful in picturing to the mind the modifications made in the classification of animals. Such a table is given on the following page.

L. Agassiz, in his famous essay on Classification, reviews in the most scholarly way the various systems of classification. One peculiar feature of Agassiz's philosophy was his adherence to the dogma of the fixity of species. The same year that his essay referred to was published (1859) appeared Darwin's _Origin of Species_. Agassiz, however, was never able to accept the idea, of the transformations of species.

Linnæus Cuvier Von Siebold Leuckart

Mammalia Vertebrata Vertebrata Vertebrata (Embracing five (Embracing five (Five classes.) Aves classes: Mammalia, classes.) Aves, Reptilia, Amphibia Batrachia, Pisces.)

Pisces

Insecta Mollusca Mollusca Mollusca (Including Crustacea, {Arthropoda etc.) Articulata {Vermes Arthropoda

Vermes Vermes {Zoöphyta {Echinoderma (Including Radiata {Coelenterata Mollusca and all {Protozoa Protozoa lower forms.)

Steps in Biological Progress from Linnæus to Darwin

The period from Linnæus to Darwin is one full of important advances for biology in general. We have considered in this chapter only those features that related to changes in the system of classification, but in the mean time the morphological and the physiological sides of biology were being advanced not only by an accumulation of facts, but by their better analysis. It is an interesting fact that, although during this period the details of the subject were greatly multiplied, progress was relatively straightforward and by a series of steps that can be clearly indicated.

It will be of advantage before the subject is taken up in its parts to give a brief forecast in which the steps of progress can be represented in outline without the confusion arising from the consideration of details. Geddes, in 1898, pointed out the steps in progress, and the account that follows is based upon his lucid analysis.

The Organism.--In the time of Linnæus the attention of naturalists was mainly given to the organism as a whole. Plants and animals were considered from the standpoint of the organism--the external features were largely dealt with, the habitat, the color, and the general appearance--features which characterize the organism as a whole. Linnæus and Jussieu represent this phase of the work, and Buffon the higher type of it. Modern studies in this line are like addition to the _Systema Naturæ_.

Organs.--The first distinct advance came in investigating animals and plants according to their structure. Instead of the complete organism, the organs of which it is composed became the chief subject of analysis. The organism was dissected, the organs were examined broadly, and those of one kind of animal and plant compared with another. This kind of comparative study centered in Cuvier, who, in the early part of the nineteenth century, founded the science of comparative anatomy of animals, and in Hofmeister, who examined the structure of plants on a basis of broad comparison.

Tissues.--Bichat, the famous contemporary of Cuvier, essayed a deeper level of analysis in directing attention to the tissues that are combined to make up the organs. He distinguished twenty-one kinds of tissues by combinations of which the organs are composed. This step laid the foundation for the science of histology, or minute anatomy. Bichat called it general anatomy (_Anatomie Générale_, 1801).

Cells.--Before long it was shown that tissues are not the real units of structure, but that they are composed of microscopic elements called cells. This level of analysis was not reached until magnifying-lenses were greatly improved--it was a product of a closer scrutiny of nature with improved instruments. The foundation of the work, especially for plants, had been laid by Leeuwenhoek, Malpighi, and Grew. But when the broad generalization, that all the tissues of animals and plants are composed of cells, was given to the world by Schleiden and Schwann, in 1838-39, the entire organization of living forms took on a new aspect. This was progress in understanding the morphology of animals and plants.

Protoplasm.--With improved microscopes and attention directed to cells, it was not long before the discovery was made that the cells as units of structure contain protoplasm. That this substance is similar in plants and animals and is the seat of all vital activity was determined chiefly by the researches of Max Schultze, published in 1861. Thus step by step, from 1758, the date of the tenth edition of the _Systema Naturæ_, to 1861, there was a progress on the morphological side, passing from the organism as a whole to organs, to tissues, to cells, and finally to protoplasm, the study of which in all its phases is the chief pursuit of biologists.

The physiological side had a parallel development. In the period of Linnæus, the physiology of the organism was investigated by Haller and his school; following him the physiology of organs and tissues was advanced by J. Müller, Bichat, and others. Later, Virchow investigated the physiology of cells, and Claude Bernard the chemical activities of protoplasm.

This set forth in outline will be amplified in the following chapters.