'52 



TYPES OF ANIMAL LIFE 



In studying the turkey we saw how all a bird's struc- 

 ture is also modified for flight, but the modifications of 

 bats and birds, though directed to the same end, are, as we 

 shall see, very different modifications. Indeed, the bat's 

 organisation, alone of existing creatures, serves to give 

 us a good conception of the wings of those ancient flying 

 reptiles, the pterodactyls. Its real affinities well serve to 

 show how little mere external aspect can be trusted as a 

 guide to fundamental relationships. The bat, as I have 

 just said, is essentially an animal formed for aerial life above 



FIG. 38. 



THE CAROLINA BAT. 



the surface of the ground. The mole is an animal formed 

 for subterranean life beneath it, and the mole as rarely 

 ascends to that surface as the bat descends to it, and 

 its structure is so efficiently modified for most rapid 

 burrowing that it may be said to fly through the earth 

 as the bat flies through the air. The bat's hand, as we 

 shall see, attains the maximum of length and slender- 

 ness, while the mole's is at a minimum of length, but is a 

 model of concentrated power. The contrast between any 

 animals could hardly be more complete ; yet the bat and 

 the mole share no small degree of affinity, and may be 

 said to be zoological cousins. 



