Ill THE SERVICE OP TAILS 85 



other lizards ; ^ and I have no disposition to deny 

 the practical service it is to the species possessing 

 such brittle tails, on the principle that a man thanks 

 his stars for the fire-escape that enables him to save 

 his life even at the expense of all his property : but 

 some of the darwinizing it has received is beyond 

 my following, at any rate. Mr. Poulton, for in- 

 stance, reasons that the very length of the tail is 

 a protective product of natural selection, it having 

 been so increased for the express purpose of 

 making it easier for an enemy to seize it, and thus 

 more surely fail (by reason of its breaking off) to 

 catch the body of the lizard; we are told that 

 " tails " on the wings of certain butterflies are made 

 conspicuous for a like reason. Then Mr. Poulton 

 goes on to argue further that the long tails charac- 

 teristic of most mice, and especially of the many 

 species which have a racket-shaped or brush-like 

 tuft of hair at the end, are due to the same influ- 

 ence : and, furthermore, that an explanation of the 

 bushy tails of the squirrel, fox, wolf, jackal, etc., 

 is contained in the same protective hypothesis. 



' It is also true of a small snail in the Philippines, whose " tail " 

 (properly the hinder end of its body or foot) will break off if seized : 

 as it is more highly colored than any other part, it is the most con- 

 spicuous point for seizure, but the bird or lizard that takes hold 

 there gets nothing but a wriggling tip for his pains, while the snail 

 drops to the ground and hides. Semper, who expounds this doc- 

 trine at length, says that he lost specimens frequently by trying to 

 pick them up by their tails ; and that ten per cent, of these snails 

 (Helicarion) showed the scar of a previous loss. 



