136 
DARWINISM 
CHAP. 
Broun relates to this very point. He states that the length of 
these organs differ in the various species of hares and of mice, 
and he considers that this difference can he of no service 
whatever to their possessors. But to this objection Darwin 
replies, that it has been shown by Dr. Schobl that the ears of 
mice “are supplied in an extraordinary manner with nerves, 
so that they no doubt serve as tactile organs.” Hence, when 
we consider the life of mice, either nocturnal or seeking their 
food in dark and confined places, the length of the ears 
may be in each case adapted to the particular habits and 
surroundings of the species. Again, the tail, in the larger 
mammals, often serves the purpose of driving off' Hies and 
other insects from the body ; and when we consider in how 
many parts of the world flies are injurious or even fatal to 
large mammals, we see that the peculiar characteristics of this 
organ may in each case have been adapted to its requirements 
in the particular area where the species was developed. The 
tail is also believed to have some use as a balancing organ, 
which assists an animal to turn easily and rapidly, much as 
our arms are used when running; while in whole groups it is 
a prehensile organ, and has become modified in accordance 
with the habits and needs of each species. In the case of 
mice it is thus used by the young. Darwin informs us that 
the late Professor Henslow kept some harvest-mice in con¬ 
finement, and observed that they frequently curled their tails 
round the branches of a bush placed in the cage, and thus 
aided themselves in climbing; while Dr. Gunther has actually 
seen a mouse suspend itself by the tail ( Origin , p. 189). 
Again, Mr. Lawson Tait has called attention to the use of 
the tail in the cat, squirrel, yak, and many other animals as 
a means of preserving the heat of the body during the 
nocturnal and the winter sleep. He says, that in cold weather 
animals with long or bushy tails will be found lying curled up, 
with their tails carefully laid over their feet like a rug, and 
with their noses buried in the fur of the tail, which is thus 
used exactly in the same way and for the same purpose as we 
use respirators. 1 
Another illustration is furnished by the horns of deer 
which, especially when very large, have been supposed to be 
1 Nature, vol. xx. p. 603. 
