256 THE HAUNTS OF LIFE 
be carried without impeding her flight. Thus 
the bats, though belonging to a class nearly 
all of the members of which live on land,: 
have become thoroughly adapted to aerial life. 
In insect-catching bats the skin is continued 
from the hind-legs to the well-developed tail, 
and this “inter-femoral membrane” forms a 
very useful pouch. For when the bat has 
caught a good-sized insect, such as a night- 
flying beetle, the difficulty arises of crunching 
it without letting it go from the grip of the 
jaws. In her delightful Wild Animals of 
Garden and Hedgerow (1920), Miss Frances 
Pitt points out that the bat lowers its head to 
its skin-basket and, pressing its booty against 
that, can crunch it comfortably without risk of 
losing what it has gained. During this process, 
which is quickly over, the bat tumbles a little 
in the air, but speedily recovers itself. 
FITNESSES OF BIRDS AND BATS 
Birds and bats are not in any way related to 
one another, except that the two classes, birds 
and mammals, may be traced back to a com- 
mon ancestry in extinct reptiles. It is all the 
more interesting to find that similar fitnesses or 
