48 



Cheiroptera.- 



-MAMMALIA.- 



-Cheiropteka. 



Order III.-CHEIEOPTEEA. 



To this small and well-marked class of mammals, it 

 must be confessed, naturalists have not given that 

 attention which the subject demands. Though for the, 

 most part composed of individuals of comparatively 

 insignificant bulk, they have nevertheless important 

 claims upon our consideration, both on account of the 

 singular and characteristic modifications of organic 

 structure they exhibit, and in respect of the part they 

 play in the economy of creation. 



With regard to the habits of the bats and their man- 

 ner of living, the first and most conspicuous peculiarity 

 presented to ordinary observation has reference to their 

 mode of flight, and the agency by which this function 

 is performed. As the majority of our readers are 

 aware, their titular name Cheiroptera, or Wing-handed 

 family, points at once to the members of the body, 

 primarily concerned in the office of flying ; but while 

 the flight of birds is immediately brought about by a 

 development of special integumentary appendages in 

 the form of feathers, we have here the same purpose 

 served by a membranous extension of the skin itself. 

 The membrane is extremely delicate and elastic, 

 extending in front from the neck and sides of the body 

 to the extremity of the fingers of each upper limb, and 

 behind to the tail and to the heels of the feet. It is 

 thus that nature displays her indefinite resources, being 

 iu no way hindered by such arbitrary laws as operate 

 in the fabrication of works of art. Look at the char- 

 acter of a bat's flight. Generally speaking its aerial 

 progression is easy, regular, and sustained. It has a 

 velocity sufficient to insure the overtaking and capture 

 of its swiftest insect prey ; while its strength is such as 

 to enable the maternal parent to carry one or two 

 young ones on her back at the same time, during her 

 passage through the air. Considering the solidity of 

 their bony framework, and the absence of such air 

 cavities as are found in birds, it would at first sight 

 appear that bats have relatively a greater specific 

 gravity than birds, and consequently a greater degree 

 of aerial pressure to contend with. This apparent dis- 

 advantage, hoAvever, is more than coimterbalanced by 

 a proportionably greater extent of surface presented by 

 the wings as compared with the weight of the body, 

 than obtains in the feathered tribe. We have here in 

 short all the essential conditions for a rapid aerial pro- 

 gression, namely, an appropriate form, a weak specific 

 gravity, and a special modification of the anterior loco- 

 motive organs, forming an elastic extensile membrane. 

 These conditions enable the Cheiroptera to realize a 

 capacity of flight second only in degree of perfection to 

 that of birds. In no other family of the first great 

 division of the animal kingdom is this physiological 

 action witnessed, unless indeed we are to exalt the 

 leaping powers of the Galeopitliccus volans to a species 

 of flight. This animal, more familiarly known as the 

 flying cat, or flying lemur, is also provided with 

 an elastic membrane of a more limited extent than 

 that of bats, but covering and connecting together the 

 anterior and posterior extremities ; this structure is not 



only incapable of raising the creature in the air, but 

 performs rather the office of a parachute than that of 

 an organ of flight. 



The remarkable adaptations thus rendered subser- 

 vient to the purposes of flight, are further, and perhaps 

 more cogently, illustrated by referring to the skeleton 

 (Plate 34, fig. 110). Here we find the solid framework 

 of the body more or less attenuated iu all its elements, 

 with the view of imparting lightness on the one hand, 

 and of retaining sti-ength on the other. Every bone 

 indicates the care taken to provide against any unne- 

 cessary weight. The skull is elongated from before 

 backwards, and its constituent parts thinned out iu a 

 striking manner; this elongation, however, is less con- 

 spicuous in those bats which feed on insects, and there 

 are several other cranial peculiarities indicating greater 

 strength in the insectivorous than in the frugivorous 

 species. Among these may be mentioned an increased 

 breadth in the form of the jaws iu the carnivorous kiud, 

 this group also having the cusps of the teeth sharp and 

 pointed, while those of the fruit-eating sectiou are 

 broader, blunter, and deeply grooved longitudinally. 

 All the bats display four canine teeth, but the number 

 of incisors and molars or grinding teeth varies consider- 

 ably. Of the latter there are never less than three on 

 either side of each jaw, while very frequently we find 

 fis'C in the upper and six iu the lower, an arrangement 

 which is occasionally reversed. With regard to the 

 incisors, or cutting teeth, there are usually two or four 

 in the upper jaw, and two, four, or sometimes six, in 

 the inferior jaw. The backbone, or chain of bones, 

 termed the vertebral column is chiefly remarkable lur 

 the large size of its spinal or neural canal, and the 

 comparative breadth and strength of the bones of the 

 neck. The vertebrae, to which the ribs are attached 

 are eleven or twelve in number, according to circum- 

 stances ; but those succeeding are more variable in this 

 respect, from four to seven being assigned to this so 

 called lumbar region. The bones of the tail, or coccy- 

 geal vertebrie, exhibit a still more striking irregularity, 

 and present, as it were, a gradual dwindling awaj' 

 towards the delicate filamentary extremity in those 

 species of Vespertilio where they are most numerous. 

 In the genus Pteropus, indeed, there is no tail what- 

 ever, but in the species of Noctula we find six bones, 

 while as many as twelve occur in the genus above 

 mentioned. All the ribs, with the exception of the first 

 pair, have an extraordinary length, relatively more, we 

 may say, than occurs in any other mammalian family. 

 The breastbone, or sternum, is also unusually long and 

 broad, the anterior part, or manubrium, as it is called, 

 having a surprising lateral expansion in certain of the 

 genera, and most conspicuously so in the horse-shoe 

 bats. In all the species this portion of the little flat 

 chain of bones, collectively termed the sternum, is pro- 

 vided with a more or less prominent central ridge on 

 the under surface, evidently corresponding to the exag- 

 gerated keel-like process developed in birds to give 

 attachment to the strong pectoral muscles. We also 



