Part 54

The last subfamily is that of the _Molossinae_, included by Dobson in the family _Emballonuridae_. In this group the premaxillae are in contact or but very slightly separated; the ears are large, with the tragus small; the dental formula is _i._ 1/1 (1/2 or 1/3), _c._ 1/1, _p._ 1/2 (2/2), _m._ 3/3; and the fibula is strongly developed. In their blunt muzzles and many other features these bats undoubtedly resemble the _Emballonuridae_, from the typical members of which they differ by the production of the thick tail far beyond the margin of the interfemoral membrane. They are further characterized by their broad and stout feet, in which the first, and in most cases also the fifth, toe is thicker than the rest, and furnished with long bent hairs; and by the presence of callosities at the base of the thumbs, and a single pair of large upper incisors occupying the centre of the space between the canines. The feet are free from the wing-membrane, which folds up under the fore-arm and legs; the interfemoral membrane is retractile, being movable backwards and forwards along the tail; this power of varying its superficial extent confers on these bats great dexterity in changing the direction of flight. All are able to walk or crawl well, and spend much of their time on trees. The genus _Chiromeles_, with _i._ 1/1, _c._ 1/1, _p._ 1/2, _m._ 3/3, the first hind-toe much larger than and separate from the others, and the widely sundered ears, is represented by _C. torquata_, a large bat of peculiar aspect, inhabiting the Indo-Malay countries. This species is nearly naked, a collar only of thinly spread hairs half surrounding the neck, and is remarkable for its enormous throat-sac and nursing-pouches. The former consists of a semicircular fold of skin forming a pouch round the neck beneath, concealing the orifices of subcutaneous pectoral glands which discharge an oily fluid of offensive smell. The nursing-pouch is formed on each side by an extension of a fold of skin from the side of the body to the inferior surfaces of the humerus and femur. In the anterior part of this pouch the teat is placed. The typical genus _Molossus_ (fig. 21) includes the mastiff-bats, characterized by the dental formula _i._ 1/1 or 1/2, _p._ 1/2 or 2/2; and by the upper incisors being close together in front. The genus is restricted to the tropical and subtropical regions of the New World. _M. obscurus_, a small species common in tropical America, inhabits the hollow trunks of palms and other trees and the roofs of houses. The males and females live apart (as is the case in most if not all bats). In West Africa the mastiff-bats are represented by _Eomops_, with one species; while _Nyctinomops_ includes a number of tropical American species more nearly related to the next genus, in which some of them (fig. 22) were formerly included. The widely spread _Nyctinomus_, with _i._ 1/3 or 1/2, _p._ 2/2 or 1/2, and the upper incisors separate in front, includes numerous species inhabiting the tropical and subtropical parts of both hemispheres. The lips of the bats of this genus are even more expansible than in _Molossus_, in many of the species (fig. 22) showing vertical wrinkles. _N. toeniotis_ (or _cestonii_), one of the largest species, alone extends into Europe, as far north as Switzerland. _N. johorensis_, from the Malay Peninsula, is remarkable for the extraordinary form of its ears. _N. brasiliensis_ is common in tropical America, and extends as far north as California.

Myzopoda and Mystacops.

Here may be conveniently noticed two very rare and aberrant bats, _Myzopoda_ (or _Myxopoda_) _aurita_ of Madagascar, and _Mystacops_ (or _Mystacina_) _tuberculatas_ of New Zealand, the latter of which is believed to be well-nigh, if not entirely, exterminated. Their systematic position and affinities are somewhat uncertain; but in the opinion of O. Thomas[2] the former should typify a separate family, _Myzopodidae_, in which the latter may also find a place. From all other bats _Myzopoda_ is distinguished by the presence of a peculiar mushroom-shaped organ at the base of the large ear, and by the union of the tragus with the latter, on the inner base of which it forms a small projection. There are three phalanges in the middle finger; and the whole inferior surface of the thumb supports a large sessile horseshoe-shaped adhesive pad, with the circular margin directed forwards and notched along its edge, while a smaller pad occupies part of the sole of the hind-foot. Mr Thomas regards this bat as related on the one hand to the subfamily _Mormopsinae_ of the _Phyllostomatidae_, and on the other to the _Natalinae_ among the _Vespertilionidae_; both these groups being regarded by him as of family rank.

_Mystacops_ resembles _Myzopoda_ in having three phalanges to the middle finger, but differs in that the tail perforates the interfemoral membrane to appear on its upper surface in the manner characteristic of the _Emballonuridae_. The greater part of the wing-membrane is exceedingly thin, but a narrow portion along the fore-arm, the sides of the body, and the legs, is thick and leathery, and beneath this thickened portion the wings are folded. Other peculiarities of structure are found in the form of the claws of the thumbs and toes, each of which has a small heel projecting from its concave surface near the base, also in the sole of the foot and inferior surface of the leg, as shown in fig. 23. The plantar surface, including the toes, is covered with soft and very lax, deeply wrinkled skin, and each toe is marked by a central longitudinal groove with short grooves at right angles to it. The lax wrinkled integument is continued along the inferior flattened surface of the ankle and leg. These peculiarities appear to be related to climbing habits in the species.

_Extinct Bats_.

Palaeontology tells us nothing with regard to the origin of the Chiroptera, all the known fossil species, some of which date back to the Oligocene, being more or less closely allied to existing types, and therefore of comparatively little interest. The origin of the order from primitive insectivorous mammals must have taken place at least as early as the Lower Eocene. It is, however, noteworthy that several of the earlier extinct species appear to be related to the _Rhinolophidae_, which is the most generalized family of the order. Remains of _Pteropodidae_ belonging to existing genera occur in the caves of tropical countries in the eastern hemisphere; and the skeleton of an extinct generic type, _Archaeopteropus_, has been obtained from the Miocene lignite of Italy, which indicates a form to a certain extent transitional in character between typical fruit-bats and the insectivorous bats. The tail, for instance, which in most modern fruit-bats is rudimentary, with only three or four vertebrae, in the fossil has eight complete vertebrae; while the teeth of the extinct form are distinctly cusped. Whether, however, the tail is longer than in the existing _Notopteris_ of Fiji and New Guinea, or whether the molars are more distinctly cusped than is the case with the Solomon Island _Pteropus_ (_Pteralopex_), is not stated. Still, the fact that the Miocene fruit-bat does show certain signs of approximation to the insectivorous (and more generalized) section of the order is of interest. Of the Oligocene forms, _Pseudorhinolophus_ of Europe is apparently a member of the _Rhinolophidae_; but the affinities of _Alastor_ and _Vespertiliavus_, which are likewise European, are more doubtful, although the latter may be related to _Taphozous_. The North American _Vespertilio_ (_Vesperugo_) _anemophilus_ and the European _V. aquensis_ and _V. parisiensis_ are, on the other hand, members of the _Vespertilionidae_, the last being apparently allied to the serotine (_V. serotinus_).

AUTHORITIES.--The above article is based to some extent on the article in the 9th edition of this work by G.E. Dobson, whose British Museum "Catalogue" is, however, now obsolete. Professor H. Winge's "Jordfundae og nulevende Flagermus (Chiroptera)," published in _E. Mus. Lundi_ (Copenhagen, 1892), contains much valuable information; and for _Pteropodidae_ Dr P. Matschie's _Megachiroptera_ (Berlin, 1899), should be consulted. For the rest the student must refer to namerous papers by G.M. Allen, K. Andersen, F.A. Jentink, G.S. Miller, T.S. Palmer, A.G. Rehn, O. Thomas and others, in various English and American zoological serials, all of which are quoted in the volumes of the _Zoological Record_. (R. L.*)

FOOTNOTES:

[1] _Bull. Amer. Mus. Nat. Hist._ vol. xii. (1899).

[2] _Proc. Zool. Soc._ (London, 1904), vol. ii.

CHIRU, a graceful Tibetan antelope (_Pantholops Hodgsoni_), of which the bucks are armed with long, slender and heavily-ridged horns of an altogether peculiar type, while the does are hornless. Possibly this handsome antelope may be the original of the mythical unicorn, a single buck when seen in profile looking exactly as if it had but one long straight horn. Although far from uncommon, chiru are very wary, and consequently difficult to approach. They are generally found in small parties, although occasionally in herds. They inhabit the desolate plateau of Tibet, at elevations of between 13,000 and 18,000 ft., and, like all Tibetan animals, have a firm thick coat, formed in this instance of close woolly hair of a grey fawn-colour. The most peculiar feature about the chiru is, however, its swollen, puffy nose, which is probably connected with breathing a highly rarefied atmosphere. A second antelope inhabiting the same country as the chiru is the goa (_Gazella picticaudata_), a member of the gazelle group characterized by the peculiar form of the horns of the bucks and certain features of coloration, whereby it is markedly distinguished from all its kindred save one or two other central Asian species. The chiru, which belongs to the typical or antilopine section of antelopes, is probably allied to the saiga. (R. L.*)

CHIRURGEON, one whose profession it is to cure disease by operating with the hand. The word in its original form is now obsolete. It derives from the Mid. Eng. _cirurgien_ or _sirurgien_, through the Fr. from the Gr. [Greek: cheirourgos], one who operates with the hand (from [Greek: cheir], hand, [Greek: ergon], work); from the early form is derived the modern word "surgeon." "Chirurgeon" is a 16th century reversion to the Greek origin. (See SURGERY.)

CHISEL (from the O. Fr. _cisel_, modern _ciseau_, Late Lat. _cisellum_, a cutting tool, from _caedere_, to cut), a sharp-edged tool for cutting metal, wood or stone. There are numerous varieties of chisels used in different trades; the carpenter's chisel is wooden-handled with a straight edge, transverse to the axis and bevelled on one side; stone masons' chisels are bevelled on both sides, and others have oblique, concave or convex edges. A chisel with a semicircular blade is called a "gouge." The tool is worked either by hand-pressure or by blows from a hammer or mallet. The "cold chisel" has a steel edge, highly tempered to cut unheated metal. (See TOOL.)

CHISLEHURST, an urban district in the Sevenoaks parliamentary division of Kent, England, 11-1/4 m. S.E. of London, by the South-Eastern & Chatham railway. Pop. (1901) 7429. It is situated 300 ft. above sea-level, on a common of furze and heather in the midst of picturesque country. The church of St Nicholas (Perpendicular with Early English portions, but much restored) has a tomb of the Walsingham family, who had a lease of the manor from Elizabeth; Sir Francis Walsingham, the statesman, being born here in 1536. Another statesman of the same age, Sir Nicholas Bacon, was born here in 1510. Near the church is an ancient cockpit. The mortuary chapel attached to the Roman Catholic church of St Mary was built to receive the body of Napoleon III., who died at Camden Place in 1873; and that of his son was brought hither in 1879. Both were afterwards removed to the memorial chapel at Farnborough in Hampshire. Camden Place was built by William Camden, the antiquary, in 1609, and in 1765 gave the title of Baron Camden to Lord Chancellor Pratt. The house was the residence not only of Napoleon III., but of the empress Eugénie and of the prince imperial, who is commemorated by a memorial cross on Chislehurst Common. The house and grounds are now occupied by a golf club. There are many villa residences in the neighbourhood of Chislehurst.

CHISWICK, an urban district in the Ealing parliamentary division of Middlesex, England, suburban to London, on the Thames, 7½ m. W. by S. of St Paul's cathedral. Pop. (1901) 29,809. The locality is largely residential, but there are breweries, and the marine engineering works of Messrs Thornycroft on the river. Chiswick House, a seat of the duke of Devonshire, is surrounded by beautiful grounds; here died Fox (1806) and Canning (1827). The gardens near belonged till 1903 to the Royal Horticultural Society. The church of St Nicholas has ancient portions, and in the churchyard is the tomb of William Hogarth the painter, with commemorative lines by David Garrick. Hogarth's house is close at hand. Chiswick Hall, no longer extant, was formerly a country seat for the masters and sanatorium for the scholars of Westminster school. Here in 1811 the Chiswick Press was founded by Charles Whittingham the elder, an eminent printer (d. 1840).

CHITA, a town of east Siberia, capital of Transbaikalia, on the Siberian railway, 500 m. E. of Irkutsk, on the Chita river, half a mile above its confluence with the Ingoda. Pop. (1883) 12,600; (1897) 11,480. The Imperial Russian Geographical Society has a museum here. Several of the palace revolutionaries, known as Decembrists, were banished to this place from St Petersburg in consequence of the conspiracy of December 1825. The inhabitants support themselves by agriculture and by trade in furs, cattle, hides and tallow bought from the Buriats, and in manufactured wares imported from Russia and west Siberia.

CHITALDRUG, a district and town in the native state of Mysore, India. The district has an area of 4022 sq. m. and a population (1901) of 498,795. It is distinguished by its low rainfall and arid soil. It lies within the valley of the Vedavati or Hagari river, mostly dry in the hot season. Several parallel chains of hills, reaching an extreme height of 3800 ft., cross the district; otherwise it is a plain. The chief crops are cotton and flax; the chief manufactures are blankets and cotton cloth. The west of the district is served by the Southern Mahratta railway. The largest town in the district is Davangere (pop. 10,402). The town of CHITALDRUG, which is the district headquarters (pop. 1901, 5792), was formerly a military cantonment, but this was abandoned on account of its unhealthiness. It has massive fortifications erected under Hyder Ali and Tippoo Sahib towards the close of the 18th century; and near it on the west are remains of a city of the 2nd century A.D.

CHITON, the name[1] given to fairly common littoral animals of rather small size which belong to the phylum Mollusca, and, in the possession of a radula in the buccal cavity, resemble more especially the Gastropoda. Their most important characteristic in comparison with the latter is that they are, both in external and internal structure, bilaterally symmetrical. The dorsal integument or mantle bears, not a simple shell, but eight calcareous plates in longitudinal series articulating with each other. The ventral surface forms a flat creeping "foot," and between mantle and foot is a pallial groove in which there is on each side a series of gills. Originally the Chitons were placed with the limpets, _Patella_, in Cuvier's _Cyclobranchia_, an order of the Gastropoda. In 1876 H. von Jhering demonstrated the affinities of _Neomenia_ and _Chaetoderma_, vermiform animals destitute of shell, with the Chitons, and placed them all in a division of worms which he named Amphineura. The discovery by A.A.W. Hubrecht in 1881 of a typical molluscan radula and odontophore in a new genus _Proneomenia_, allied to _Neomenia_, showed that the whole group belonged to the Mollusca. E. Ray Lankester (_Ency. Brit._, 9th ed., 1883) placed them under the name Isopleura as a subclass of Gastropoda. Paul Pelseneer (1906) raised the group to the rank of a class of Mollusca, under von Jhering's name Amphineura.

The Amphineura are divided into two orders: (1) the Polyplacophora, or Chitons; (2) the Aplacophora, or forms without shells, _Neomenia_, _Chaetoderma_ and their allies.

Order I.--POLYPLACOPHORA

Each of the eight valves of the shell is made up of two distinct calcareous layers: (a) an outer or upper called the tegmentum, which is visible externally; (b) a deeper layer called articulamentum which is porcellaneous, quite compact, and entirely covered by the tegmentum. In the lower forms the two layers are coextensive and have smooth edges, but in the higher forms the articulamentum projects laterally beyond and beneath the tegmentum into the substance of the mantle. These projections are termed insertion plates; they are usually slit or notched to form teeth, the edges of which may be smooth and sharp, or may be crenulated. The anterior margin of each valve except the first is provided with two projections called sutural laminae which underlie the posterior margin of the preceding valve.

The tegmentum is formed by the fold of mantle covering the edge of the articulamentum, and extends over the latter from the sides. It is the first part of the shell formed in development. The tegmentum is much reduced in _Acanthochiton_, and absent in the adult _Cryptochiton_. The tegmentum is pierced by numerous vertical ramified canals which contain epithelial papillae of the epidermis. These papillae form pallial sense-organs, containing nerve-end bulbs, covered by a dome of cuticle, and innervated from the pallial nerve-cords. They are termed according to their size, micraesthetes and megalaesthetes. In the common species of _Chiton_ and many others of the family _Chitonidae_ the megalaesthetes are developed into definite eyes, the most complicated of which have retina, pigment within the eye, cornea and crystalline lens (intra-pigmental eyes) (fig. 2). The eyes are arranged in rows running diagonally from the median anterior beak of each valve to its lateral borders There may be only one such row on either side, or many rows. In some species the total number present amounts to thousands.

A. Neomenia and Proneomenia. B. Chaetoderma. C. Chiton. _o_, Mouth. _a_, Anus. _d_, Alimentary canal. _l_, Liver (digestive gland).]

_Branchiae._--The series of gills may extend the whole length of the body in the pallial groove, or may be confined to the posterior end. Each gill has the structure of a typical molluscan ctenidium, consisting of an axis bearing an anterior and posterior row of filaments or lamellae. The gills are thus metamerically repeated; there may be from four to eighty pairs, but there is often a numerical asymmetry on the two sides. The largest pair of branchiae is placed immediately behind the renal openings and corresponds to the single pair of other molluscs, the organs being repeated anteriorly only (Metamacrobranchs) or anteriorly and posteriorly (Mesomacrobranchs).

_Intestine._--The digestive tube in the Polyplacophora, which are herbivorous, is longer than the body, and thrown into a few coils, the anus being median and posterior. The mouth leads into the buccal cavity, on the ventral side of which opens the radular caecum. Each transverse row of teeth of the radula contains 17 teeth, one of which is median, while the second and the fifth on each side are enlarged. Two pairs of glands open into the buccal cavity, and at the junction of pharynx and oesophagus is another pair called the sugar glands. The stomach is surrounded by the liver or digestive gland, consisting of two lobes which are symmetrical in the young animals, but in the adult the right lobe is anterior and smaller.

_Coelom, Gonads and Excretory Organs._--As in other molluscs the coelom is represented by a large pericardial cavity, situated above the intestine posteriorly, and a generative sac which is single and median and situated in front of the pericardium, except in the _Nuttalochiton hyadesi_, where the gonads are in a similar position, but are paired. The excretory organs are coelomoducts with an internal ciliated opening into the pericardium and an opening to the exterior. Both the openings are close together, the external opening being just in front of the principal gill near the posterior end of the body. The renal tube is doubled on itself, its middle part where the bend occurs being situated more or less anteriorly. The excretory surface is increased by numerous ramified caeca which extend beneath the body wall laterally and ventrally, and open into the tube (fig. 6). The sexes are distinct, and the ovary is frequently greenish in colour, the testis red. The gonad is transversely wrinkled and lies between the aorta and the intestine, extending from the pericardium to the anterior end of the body. A simple gonaduct on each side arises from the gonad near its posterior end and passes first forwards, then backwards, and lastly outwards to the external opening in the pallial groove, anterior to the renal aperture. There may be from one to nine gills between the genital and renal pores.