38 BOMBAY DUCKS 
have lost not only their sight, but even their eyes. 
Man’s tail became useless to him, so has disappeared. 
The whale’s legs were no longer needed when it took 
to an aquatic life; they were, therefore, transformed 
into fins, 
Thus it is probable that, if the tails of the mouse 
and the rat served no useful purpose, these animals 
would long ago have been reduced to the state of the 
guinea-pig. What, then, is the use of the tail in each 
case? This is, indeed, a problem. These creatures, 
being nocturnal in their habits, do not afford the 
naturalist many opportunities of watching them. 
Nevertheless, they move in such a rapid, silent, 
mysterious way that it is more than possible that the 
long supple tail assists them during locomotion. 
