INTRODUCTION. xvii but probably much more effective than the vibriss of other species, supplementing in the animals in which they are developed the feeble aid given by the small eyes in distinguishing objects approached in rapid flight during the hours of darkness*.
In all species of Bats with nasal appendages there may be found more or less well-developed glandular prominences on the sides of the face between the eyes and the extremity of the muzzle. In some genera they are small and concealed by the fur (as in Vespertilio and Kerivoula), in others large and nearly naked, forming prominent rounded elevations (as in Vesperugo, Plecotus, and Synotus), but in all long and straight fine hairs arise from them, which are evidently analogous and homologous to the vibrisse of the Felide and other Mammals. In some specimens of Plecotus awritus these glands are found unusually large, forming rounded prominences, raised slightly above the margins of the naked crescentic depressions behind the nostrils (Plate XI. fig. 9). These prominences in Plecotus (Corinorhinus) macrotis are greatly developed vertically, forming high conical processes which, bending inwards over the nasal grooves, meet in the centre above and behind the nostrils, concealing the grooves beneath (Plate XI. fig. 8). In front the nasal apertures in this species are margined by a narrow, flat, cutaneous ring. In Myctophilus (which is closely related to Plecotus and Synotus) the same prominent glands of the muzzle have become united in the centre above (evidence of their distinct origin being still afforded by the presence of a longitudinal furrow above), while the cutaneous marginal rings surrounding the nasal apertures in P. macrotis are here expanded and united together above and behind the nostrils, forming a small nose-leaf, which is supported behind by the united glandular prominences (Plate XI. fig. 7). In the much more highly differentiated nasal processes of Megaderma, especially of M. spasma, the homologies of these parts with the glandular prominences and rudimentary nose-leaf of Vyctophilus may be easily recognised. This, then, is evidently the mode in which the very complicated nasal appendages of Rhinolophus and other genera have originated, whence it follows that they are partly composed of the marginal in- * Bats without nasal appendages are more properly crepuscular and matutinal than nocturnal in their habits (see description of habits of Molossus obscurus, p-412). The nose-leafed species fly much later, and this is probably one of the reasons why they are less commonly shot on the wing. Mr. Tomes has noted the much finer sense of touch possessed by a leaf-nosed Bat, as shown when flying in company with a simple-nosed Bat in a confined space.
xVill INTRODUCTION.
tegument of the nostrils, partly of highly differentiated gland structures; and investigation of their minute structure confirms this deduction*.
In all species of leaf-nosed Bats, and especially so in the Rhinolophide, in which the nasal appendages reach their highest development, the superior maxillary division of the fifth nerve is of remarkably large calibre, as, indeed, the size of the infraorbital foramen shows. ‘The nasal branch of this nerve, which is given off immediately beyond the infraorbital foramen, is by far the largest portion, the palpebral and labial branches consisting of a few slender nervefibres only. This branch passes forwards and upwards on the side of the superior maxillary bone, but soon spreads out into numerous filaments, which pass into the muscles and integument above and into the base of the nose-leaf. The nerve supply of the nose-leaf is further considerably augmented by the large nasal branch of the ophthalmic division of the fifth nerve.
While the many foliations, elevations, and depressions which vary the form of the nose-leaf also greatly increase the sensory surface so abundantly supplied by the fifth nerve and in rapid flight intensify the vibrations conveyed to it, the great number of sweat- and oil-glands which enter into its structure perform an important function, analogous to that of the glands of the auditory canal in relation to the membrana tympani, in maintaining its surface in a soft and highly sensitive condition.
The nasal appendages of Chiroptera, then, may be regarded as performing the office of an organ of a very exalted sense of touch, standing in the same relation to the nasal branches of the sensory divisions of the fifth nerve as the aural apparatus to the auditory * The minute anatomy of the nasal appendages of Rhinolophus hipposideros (as regards their cutaneous, muscular, and glandular structures) has been well worked out by Dr. Redtel (Zeitschr. fiir wissench. Zool. 1873, pp. 254-288, pl. xiv.), who describes the extraordinary richness of these parts in glands, which he divides into two classes—‘‘ Talgdriisen ” and ‘“ Schweissdriisen.” He hazards, however, no opinion as to their mode of origin or functions. t In the Rhinolophide and Nycteride, owing to the position of the nasal orifices, which open so far back on the muzzle, the cup-shaped depression in which they are placed evidently corresponds to the anterior part of the nasal fosse, which in other animals is divided by a cartilaginous septum, covered in by integument, and supplied by the nasal branch of the ophthalmic division of the fifth nerve; so that here we find this highly sensitive portion of the nose freely exposed to the air, and undoubtedly constituting, in addition to the surrounding nasal appendages, an exquisitely sensitive organ of touch,
INTRODUCTION. xix nerve; for, as the latter organ collects the waves of sound, so the former receives impressions arising from vibrations communicated to the air by approaching objects.
But although the sense of touch in the leaf-nosed Bats must evidently be immensely increased by these nasal appendages, it should not be lost sight of that this sense is extremely acute also in species not provided with such special organs. In Spallanzani’s well-known experiments, the Bats which succeeded in avoiding numerous threads hung across the rooms in which, when deprived of sight, hearing, and smell, they were permitted to fly about were not leaf-nosed species; and the unerring flight of the simple-nosed Bats of this country, even in the darkest places, has been observed by almost every one. We must therefore seek for other sensory organs which supplement the sense of vision. These undoubtedly exist in the great extent and highly sensitive condition of the integument entering into the formation of the wing-membrane and ear-conch*. In many of the species of Vespertilionide also the concave surface of the large and delicately formed ear is dotted over by numerous minute glandular elevations, from which small straight hairs, evidently analogous to the vibrisse on the sides of the muzzle, arise (see Plate XVII. fig. 7).
In no order of Mammals is the ear-conch so greatly developed or so variable in form. In some of the species of the group Plecoti the length of the ear nearly equals that of the head and body, while in by far the greater number of the species of Microchiroptera the ears are as long or nearly as long as the head, and in many species they are united across the forehead. The form of the conch is very characteristic in each of the families. In Nycteride, Vespertilionide, Eimballonuride, and Phyllostomide the tragus is greatly. developed, forming in some species a long projection extending nearly to the outer margin of the conch, and its shape is generally characteristic in each species. Its office appears to be to cause undulations in the waves of sound, and so intensify and prolong them. It is worthy of notice that in the truly insectivorous Rhinolophide, where the tragus is not developed, the auditory bulle ossee reach their greatest size and the highly sensitive nasal appendages their highest development; also in the group Molossi the * See an excellent paper on the minute anatomy of the wing-membrane in Chiroptera, by J. Schdbl, in Schultze’s ‘Archiv,’ vii. (1871) pp. 1-31, in which the layers of integument, the hairs and their glands, the mode of termination of the nerves, &ec. are carefully described.
xx INTRODUCTION.
ear-conch is divided by a prominent keel, and the antitragus is remarkably large in those species in which the tragus is minute (Plate XXI. figs. 2, 3). In the frugivorous Megachiroptera, as might be expected, the form of the ear-conch is very simple and but slightly variable in all the species, and there is no tragus. Although the frugivorous and sanguivorous species of Phyllostomide have a tragus, yet in them both it and the conch are remarkably small and very similar in form, even in species otherwise differing greatly in structure, contrasting strongly with the great development of the same parts in the insectivorous species (compare Plates XXIV. and XXX.). Widely, however, as the form of the ear-conch differs in these groups, the common origin of all is shown by the general similarity of the structure of the tragus and by the presence of a peculiar ridge of integument passing obliquely upwards and forwards from the base of its inner margin on the side of the head, which is equally developed in the long-headed Glossophage and in the short-skulled Stenodermata.
In all Bats the ears are extremely mobile, each moving independently at the will of the animal. This I have observed even in the frugivorous Pteropodide, in which the peculiar vibratory movements noticed by Mr. Osburn in Artibeus perspicillatus (see p. 520 infra) may also be seen when the animals are alarmed.
Derntat SystEm.
The different forms of dentition observable in the Chiroptera will be found very fully treated of in the definitions of the families and genera and in the descriptions of the species, as in nearly all cases the dental characters afford the most reliable guides in determining their natural affinities and in their discrimination. Of the 400 species described in the following pages, at least 300 are insectivorous, and, as might be expected from the nature of their food, their molar teeth are of the insectivorous type, being acutely tubercular, with usually well-developed W-shaped cusps. ; 4 1-1 $23: 3-5 The dental formula never exceeds inc. go [p> PM. s,m. = 38 teeth*, but is frequently less than that number, falling as low as inc. 2 C. = pm. = m. $=20 teeth in the sanguivorous group Desmodontes, the variability in the number of teeth in the insectivorous species being confined chiefly to the incisors and premolars, * See footuote, p. 509, for an instance of an apparent exception to this rule,
INTRODUCTION. Xxi in the frugivorous to the posterior molars (see p. 16 and footnote, also p. 512).
Among the Microchiroptera, in the family Phyllostomide alone is there any marked departure from the insectivorous type of dentition, and there only in the limited groups Stenodermata (see Plates XXVIII. and XXIX.) and Desmodontes (see pp. 445, 511, 545), In the Megachiroptera, which are wholly frugivorous, the form of the teeth is remarkably similar throughout the different species, though their number is very variable. In all the species (except Cynopterus latidens, Plate V. fig. 3) the molar teeth are longer than broad, and their crowns are traversed by a longitudinal groove ; while among the species of Microchiroptera, in Sturnira lilium alone are the molar teeth somewhat similarly grooved (Plate XXVIII. fig. 5).
The milk-dentition is much the same in all Bats. The teeth are very slender and with acutely pointed recurved cusps, evidently very effective in retaining a secure hold on the nipple of the mother during flight. They are soon shed, but often coexist for a short time with the permanent teeth, when the latter are considerably elevated above the gum.
ALIMENTARY CANAL.
The opening of the mouth is anterior in most species, but in many of the species of Emballonuride it resembles that of the Insectivora in being inferior, the extremity of the nose being more or less produced beyond the lower lip, so much so in Rhynchonycteris naso (Plate XX. fig. 4) as to resemble that of the Shrew-mice. In the Mycteride, and in the groups Mormopes and Desmodontes, the lower lip projects slightly beyond the upper. In all the insectivorous species the gape is wide, and the lips are fringed with straight hairs and very expansible, especially in the Molossi, in many species of which they are marked by deep vertical wrinkles (Plate XXII.). In Chalinolobus a small lobe projects horizontally outwards from the lower Jip near the angle of the mouth, and adds considerably to its width. In the Mormopes the lower lip is much expanded in front and fringed with foliaceous cutaneous appendages, which probably fulfil the same functions as the nasal processes in the leaf-nosed Bats ; while in the remaining species of Phyllostomide and in the Nycteride the same part is furnished with variously c
XXii INTRODUCTION.
shaped wart-like elevations and grooves. In the long-tongued Glossophage (Plate XXVII.) the groove in the centre of the lower lip serves as a channel for the tongue, which can be thrust out between the lower canines without necessarily opening the mouth. The form of the lips is exceedingly peculiar in Noctilio, and will be found described at p. 395, and figured in Plate XX. In the Megachiroptera the form of the lips is generally less variuble, but in the genus Zpomophorus (the species of which live on juicy fruits) they are exceedingly expansible, forming deep folds and pouches especially in adult males, and in &. (Hypsignathus) monstrosus are most remarkably lobed in front. The nakedness of the lips and complete absence of a fringe of hairs is very characteristic of all fruit-eating Bats, and probably always distinguishes them from the insectivorous species which they may resemble in the form of their teeth and in other respects.
The inner margins of the lips in nearly all the frugivorous species, whether belonging to the suborders Megachiroptera or Microchiroptera, are fringed with numerous long conical papille. In all Bats palatal ridges are more or less well-defined, but are largest in Megachiroptera, and reach their highest development in the genus Epomophorus, where their form and arrangement is characteristic in each species (see p. 5, and Plate II. figs. 1-6). The cesophagus is narrow in all species, and especially so in the sanguivorous Desmodontes. The stomach presents two principal types of structure, which correspond respectively to the two great divisions of the order, the Megachiroptera and the Microchiroptera. In the former the pyloric portion is much produced and often folded upon itself; in the latter the same part is very short and the pyloric aperture close to the entrance of the cesophagus, the cardiac portion being expanded into a simple globular or oval sac, or greatly elongated, forming an intestiniform ceecum, as in the group Desmodontes. The complex form of the stomach in the frugivorous Megachiroptera is comparable to that of the Ruminantia, while the insectivorous Microchiroptera resemble the Carnivora in the simple form of the same organ.
In Pteropus the wsophagus opens into a pyriform pouch, to the left of which the cardiac portion is expanded longitudinally, but is not contracted in the middle; behind, a constriction opposite the entrance of the cesophagus indicates externally the commencement of the pyloric portion, which is immensely elongated, resembling a large colon, and is folded to the left upon itself, so that externally
INTRODUCTION. Xxiil the pyloric extremity is placed near the cesophagus; immediately before terminating at the well-marked pylorus it forms a sacculated expansion, the rounded cecal extremity of which lies externally across its inferior surface. In the closely allied genera Cynopterus and Cynonycteris the form of the stomach is very similar to that of Pteropus, the chief difference being that the cardiac portion is not distinctly separated by a notch externally, and the pyloric portion is not expanded near its termination at the pylorus. In Cephalotes the stomach is somewhat like Pteropus; the cardiac division is similarly separated, but the pyloric is very long and folded twice upon itself, and at its extremity near the pylorus is not expanded. In Epomophorus (the species of which live on soft fruit) and in Harpyia the form of the stomach is much simpler, the pyloric portion is not nearly so long nor folded upon itself, as in Pteropus, and the cardiac division is marked externally by a constriction on its left side. In the long-tongued Macroglosst the stomach varies considerably in form. In Honycteris the pyloric portion is much shorter and less folded upon itself than in Pteropus, and on the whole resembles that of Cynonycteris. In Notopteris it is quite differently shaped, and, indeed, presents a form apparently unique. It is divisible externally into three portions—a cardiac, a central, and a pyloric. The central portion, which extends backwards behind the other two, is almost globular in form and communicates directly in front with the cesophagus, on the left with the cardiac sac, and on the right with the pyloric portion, of which the proximal half lies close to the right side of the cesophagus, almost level with the cardiac portion, and becoming bent on itself to the right terminates in the pylorus, immediately beyond which the gall-duct enters the duodenum. In the Microchiroptera (with the exception of the group Desmodontes) the stomach is quite simple, and varies very slightly in the different families. In many it seems like a simple expansion on one side of the cesophagus, so closely together are the cesophageal and pyloric orifices placed. In the frugivorous species of Artibeus it somewhat approaches in structure some of the simpler forms met with in Megachiroptera, as in Harpyia, and is similarly lined with deeply reticulated mucous membrane; but the difference is still very striking. The very aberrant form of stomach in the sanguivorous Desmodontes is described at p. 548.
The intestinal canal varies considerably in length, but is generally three or four times the length of the head and body. It is characterised by remarkable uniformity in calibre from the pylorus to the c2
XxXiv INTRODUCTION.
rectum, and by the absence of a cecum and of valves*. A small caecum is said to exist in Rhinopoma, but I have not succeeded in finding one in any of the individuals of the single species of that genus examined by me; in Megaderma spasma, at a distance of about three quarters of an inch from the anus, there is a small caecumlike appendage about one tenth of an inch in length, but I have not been able to discover any opening in the intestine communicating with it.
In all species of Chiroptera the liver is remarkably large ; the left lateral lobe is always well developed, and in Microchiroptera occasionally equals half the size of the whole organ. Except in the Desmodontes, the right and left lateral fissures are very distinct, and often extend almost to its attached border. The liver of the Megachiroptera is easily distinguished from that of the Microchiroptera by the illdefined condition or absence of the Spigelian lobe, and, in some genera, by the remarkably large size of the caudate lobe, for in the Microchiroptera the Spigelian lobe is very large and lies in the triangular space between the cesophagus and the pyloric end of the stomach, while the caudate lobe is small, in most species forming a ridge only.
In Pteropus the left and right central lobes are nearly equal and are divided by a notch behind; the gall-bladder is contained in a notch in the concave upper surface of the right central lobe; the right and left lateral fissures extend almost to the attached margin of the organ; the left lateral lobe is as large as the conjoined central lobes, and greatly exceeds in superficial extent the right lateral, which is irregularly quadrilateral and thick, and its concave outer side is moulded on the right kidney ; the caudate lobe is very large and tongue-shaped, and extends backwards as far as the posterior margin of the right lateral lobe, having its outer concave side applied to the inner convex surface of the kidney ; the Spigelian lobe is very small and ill-defined. Cynopterus comes nearest to Pteropus in the form of the liver; but the caudate lobe is even larger, extending considerably behind the right lateral lobe, and having part of its free extremity moulded round the posterior surface of the kidney. In Cephalotes the caudate lobe is equally large, but the gali-bladder lies in a concavity between the right central and the * This accounts for the rapidity with which, in the frugivorous species at least, the food eaten passes through the body, and explains how the astonishing voracity of these animals is indulged in without inconvenience. (See a note on the voracity of Cynopterus marginatus, p. 83.)