1873.] CHARACTERS IN THE CHIROPTERA. 231 



are generally of an intensely black colour throughout; in a few 

 specimens only, of apparently very aged individuals, the fur on the 

 back of the head and neck has a slightly reddish tinge ; while the 

 males have the whole back of the head and nape of the neck to the 

 shoulders bright orange or pale yellow (very rarely, in old males, 

 reddish brown) as in Ft. medius, contrasting as remarkably with the 

 sombre hues of the females as the brilliantly coloured skin of the 

 male Mandrill contrasts with the same parts in the other sex. 



A review of the varieties of secondary sexual characters exhibited 

 by various species of Chiroptera described in the foregoing pages 

 shows that in almost all cases these differences depend on the pos- 

 session by the male (rarely by the female) of accessory organs, 

 generally odoriferous glands, used probably for the purpose of 

 bringing the sexes together during the rutting-season, or for exciting 

 the female ; and this might be expected in animals in which the 

 power of vision is almost entirely supplemented by an extraordinary 

 development of the senses of touch and smell. 



Differences, depending partly or entirely on the possession by the 

 male of fur of a much more brilliant hue, or distinguished by dif- 

 ferent markings, or by the greater length of certain portions, are met 

 only, to any appreciable extent, in the Frugivorous Bats, in which the 

 sense of sight is well developed*. 



The inference that will naturally be drawn from a perusal of this 

 paper will be, not only that many species of Chiroptera possess 

 well-marked secondary sexual characters, but also that several species 

 exhibit as remarkable differences in this respect as any that have 

 been observed in the whole class Mammalia. 



The danger of generalizing statements from imperfect data is thus 

 strikingly illustrated ; and we are reminded of the old axiom in logic 

 which biologists, both great and small, would do well to keep ever 

 before their minds : — " A particulari ad universale argumenturn uon 

 est." 



The science of life is yet in its infancy. Man has existed for 

 thousands, perhaps millions, of years upon the earth ; but the grand 

 question of his origin and of that of other animals is believed by 

 many distinguished biologists to have already been finally settled 

 from a consideration of a few facts collected within the past half 

 century, most of them within the past decade. 



specimen I received, a female with intensely black fur throughout, was sent ine 

 by Mr. Homfray, Assistant Superintendent, Port Blair. Other specimens, male 

 and female, were obtained by me in May last near Port Blair ; and Mr. Homfray 

 has since sent me from the Nieobars specimens of the common Flying Fox of 

 these islands, which I find in no respect different from the Andamanese species. 

 * The beard in the males of Taphozous melanopogon evidently depends on the 

 presence of a subcutaneous gland, in the position occupied by the gular pouch 

 in other species of the genus, which discharges its secretion by minute pores. 

 The long black hairs forming the beard grow about these pores, their coarseness 

 and length depending on the glandular secretion by which they are abnormally 

 nourished. 



The length of the hair composing the epaulettes of the Wptmophori is pro- 

 bably due to the same cause ; but its remarkable difference in colour requires 

 another explanation. 



