CHEIROPTERA. 135 



index with one, middle finger with three phalanges, 

 two last each with two. They prey solely on insects, 

 and inhabit every region except Australia. At all 

 periods of their lives, they have four incisors above 

 and six below : all the species have about the head 

 odoriferous glands in both sexes. 



The European Bats associate together about the 

 period of hybernation, which often continues through 

 the winter, where they link themselves together in 

 great masses of individuals, in the retreats in which 

 they are protected from cold. 



According to M. Temminck, some species bear 

 one, others two young, periodically or accidentally ; 

 all produce sometimes the former number, at others 

 the latter. This is particularly the case with the 

 common Vespertilio noctula : when rearing their 

 offspring, the females fix their arm hook, and bend 

 the tail under the abdomen, thus converting the 

 interfemoral membrane into a sack, forming a nest 

 for the young, in which it is conveyed while the 

 mother is on the wing. 



Bats Proper, and Rhinolophi, perhaps all the 

 long-tailed insectivorous Cheiroptera, use that mem- 

 ber as a finger, to introduce their prey into the 

 mouth, or rather throat, when it is of larger dimen- 

 sions than usual ; they approximate it to the head, 

 bend the neck, and thus master their insect victim ; 

 hence the tail must have considerable influence on 

 the habits of the different groups, and in true bats 

 it is always formed upon one model. 



The number of species in this genus, expunging 



