136 DARWINISM 



Bronn 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 be 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 flies 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. Giinther 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. 



