RESEMBLANCES AMONG ANIMALS. 125 



another group; and we know that the creatures re- 

 sembled, possess an immunity from attack, by their 

 being always very abundant, by their being conspi- 

 cuous and not concealing themselves, and by their 

 having generally no visible means of escape from 

 their enemies ; while, at the same time, the particular 

 quality that makes them disliked is often very clear, 

 such as a nasty taste or an indigestible hardness. 

 Further examination reveals the fact that, in several 

 cases of both kinds of disguise, it is the female only 

 that is thus disguised ; and as it can be shown that the 

 female needs protection much more than the male, 

 and that her preservation for a much longer period is 

 absolutely necessary for the continuance of the race, 

 we have an additional indication that the resemblance 

 is in all cases subservient to a great purpose the 

 preservation of the species. 



In endeavouring to explain these phenomena as 

 having been brought about by variation and natural 

 selection, we start with the fact that white varieties 

 frequently occur, and when protected from enemies 

 show no incapacity for continued existence and in- 

 crease. We know, further, that varieties of many 

 other tints occasionally occur; and as f 'the survival 

 of the fittest " must inevitably weed out those whose 

 colours are prejudicial and preserve those whose 

 colours are a safeguard, we require no other mode of 

 accounting for the protective tints of arctic and 

 desert animals. But this being granted, there is 

 such a perfectly continuous and graduated series of 



