136 DARWINISM chap. 



Bronii 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 ser\ace 

 whatever to their possessors. But to this objection Darwin 

 replies, that it has been shown by Dr. Schubl that the ears of 

 ' mice "are supplied in an extraordinary manner with nerves, 

 so that they no doubt serve as tactile organs." Hence, when 

 Ave 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 dri\ang 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, 

 Avhich assists an animal to turn easily and rapidly, much as 

 our arms are used when running ; Avhile in whole groups it is 

 a prehensile organ, and has Ijecome modified in accordance 

 with the habits and needs of each species. In the case of 

 mice it is thus used by the young. DarAvin 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). 

 V 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 preser%dng the heaf/- of the body during the 

 nocturnal and the Avinter sleep. He says, that in cold Aveather 

 animals Avith long or bushy tails aa^II be found lying curled up, 

 Avdth their tails carefully laid over their feet like a rug, and 

 Avith their noses buried in the fur of the tail, AAdiich is thus 

 used exactly in the same Avay and for the same piu'pose as Ave 

 use respirators.^ 



Another illustration is furnished l^y the horns of deer 

 Avhich, especially Avhen very large, have been supposed to be 

 ^ Xature, vol. xx. p. 603. 



