ORDER CARNASSIER. 101 



obstructed and filled by certain kinds of pipes and tunnels. 

 But as an extraordinary degree of development rarely occurs 

 in one place, without becoming an impediment elsewhere, so 

 we find that this development of the fossse nasales is in- 

 fluential on the intermaxillary bone. The latter becomes 

 smaller in proportion to the extension and prolongation of 

 the former. It is sometimes so considerably diminished as 

 to become little more than a bony point which goes off 

 and is lost in the dermis: sometimes, indeed, it is alto- 

 gether wanting. 



The incisors which necessarily follow all the conditions 

 of this organ, which become small as it lessens, and dis- 

 appear when it is gone, are, in the bats, thus crossed in 

 their development by a specific influence. They are no 

 longer obedient to the controlling power of the general or- 

 ganization, and are no longer to be received as a test of its 

 constitution. They vary, on the contrary, according to the 

 intensity of the local action which presses them, and be- 

 come a character of less value than where the natural pro- 

 gress of their growth is unimpeded. 



But though they yield in importance to the organs of 

 sense in their vicinity, they become, under a new aspect, 

 an object worthy of consideration. They serve as a medium 

 for appreciating the different modifications of these organs, 

 and, in conjunction with them, to establish the characters 

 for some particular groups and subgenera ; — and, as these 

 different modifications are also simultaneous with others, 

 which affect either the organs of digestion, the wings, the 

 tail, or the interfemoral membrane, it follows that we have 

 a certain portion of characters sufficiently elevated to ar- 

 range the bats in divisions strongly marked, and to dispose 

 them in small natural families or groups. 



M. Geoffroy has divided the bats into fifteen of these 

 groups, other naturalists have added more, and the number 

 seems likely to be augmented, as observation is extended in 



