WHAT ARE BATS ? 
239 
certain subordinate, but still very large, groups, each of which 
is called a class. 
Thus the subkingdom Vertebrata is made up of the class of 
man and beasts, that of birds, that of reptiles, that of frogs, 
toads, and efts, and that of fishes. 
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 44 species.” 
Now the bat, as already said, belongs to man’s own class, 
possessing 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, sus- 
tained 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 
extinct reptiles, the pterodactyles, these creatures have no true 
affinity. Pterodactyles are aerial modifications of the Rep- 
tilian type, just as bats are aerial modifications of the Mam- 
malian type. We may say, in a rough and general way, as 
I pterodactyles are to reptiles, so are bats to mammals. 
Before concluding, we may now glance at the question of 
the genesis or origin of bats. To those who accept the doc- 
trine of Evolution — as I myself do — there can be no question 
but that bats did arise by natural generation from some an- 
terior 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 specialised and differentiated forms were developed from 
anterior less highly specialised and differentiated ones. We 
may do so, e.g ., as regards the horse and the ox. But we cannot 
do so as regards the bat, because up to the present time no 
fossil remains whatever have been found which connect bats 
with other creatures. Moreover, the development of the bat’s 
wing, difficult as it is to conceive upon any view of evolution, 
seems to me to be especially 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 relatives of 
the bat which are not bats are perhaps the little shrew mice 
belonging to the order Insectivora. Some of these are aquatic; 
