NATURAL SELECTION 



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 dis- 

 guise, 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 increase. We know, further, that 

 varieties of many other tints occasionally occur ; and as " 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 account- 

 ing for the protective tints of arctic and desert animals. 

 But this being granted, there is such a perfectly continuous 

 and graduated series of examples of every kind of protective 

 imitation, up to the most wonderful cases of what is termed 

 " mimicry," that we can find no place at which to draw the 

 line, and say : So far variation and natural selection will 

 account for the phenomena, but for all the rest we require a 

 more potent cause. The counter theories that have been 

 proposed, that of the " special creation " of each imitative 

 form, that of the action of " similar conditions of existence " 

 for some of the cases, and of the laws of " hereditary descent 

 and the reversion to ancestral forms " for others, have all 

 been shown to be beset with difficulties, and the two latter 

 to be directly contradicted by some of the most constant and 

 most remarkable of the facts to be accounted for. 



General deductions as to Colour in Nature 



The important part that "protective resemblance" has 



played in determining the colours and markings of many 



groups of animals, will enable us to understand the meaning 



of one of the most striking facts in nature, the uniformity in 



