538 THE POPULAR SCIENCE MONTHLY. 



Every class is again subdivided into certain subordinate groups, 

 termed orders. 



Each order is composed of families, each family of genera, and 

 each genus of its component kinds or " species." 



Now, the bat, as already said, belongs to man's own class, possess- 

 ing as it does all the characters which distinguish that class from the 

 other classes of vertebrate animals. 



Man's own class, Mammalia, is divisible into some dozen orders, 

 and all the bats form one such order (Cheiroptera), into which no 

 animal but a bat is admitted. The characters of this order are the 

 possession of a truly flying membrane, sustained by very elongated 

 fingers ; and the bat is capable of being very shortly defined, namely, 

 as a truly flying mammal. 



Bats present no real resemblance whatever to birds, but are, of 

 course, much more like ourselves (who are their class-fellows) than 

 they are like any bird. 



Similarly, in spite of this analogical relation of bats to those ex- 

 tinct reptiles, the pterodactyls, these creatures have no true afiinity. 

 Pterodactyls are aerial modifications of the Reptilian type, just as 

 bats are aerial modifications of the Mammalian type. We may say, 

 in a rough and general way, as pterodactyls are to reptiles, so are 

 bats to mammals. 



Before concluding we may now glance at the question of the gene- 

 sis or origin of bats. To those who accept the doctrine of Evolution 

 as I myself do there can be no question but that bats did arise by 

 natural generation from some anterior beasts which were not bats. 

 But at what period and from what progenitors ? these are questions 

 which it is quite impossible to answer at present. As has been said, 

 there are certain cases in which we may imagine now existing more 

 highly specialized and differentiated forms were developed from ante- 

 rior less highly specialized and differentiated ones. We may do so, 

 e. g., as regards the horse and the ox. But we cannot do so as re- 

 gards the bat, because up to the present time no fossil remains what- 

 ever have been found which connect bats with other creatures. More- 

 over, the development of the bat's wing, difficult as it is to conceive 

 upon any view of evolution, seems to me to be esj)ecially difficult as 

 the mere result of the survival of the fittest, when we consider the 

 origin of the initial stages of the organ. The nearest existing rela- 

 tives of the bats which are not bats are perhaps the little shrew-mice 

 belonging to the order Insectivora. Some of these are aquatic ; and 

 it is conceivable, though there is no fragment of evidence in favor of 

 it, that some ancestral aquatic form may have developed long fingers 

 and webs like those of the flying-frog. This speculation does not, 

 however, commend itself to my mind as a satisfactory one ; and 

 though, doubtless, could we see all the extinct forms of life which 

 have existed during the secondary period, we should find some creat- 



