38 THE INFANCY OF ANIMALS 



destroy its contours, hence they are called " secant " 

 patterns — they begin to disintegrate ; though the process 

 of their decay may be infinitely slow. But so long as 

 and in so far as they confer benefits, so long and so far 

 will they be retained. 



What, then, regulates their persistence ? what deter- 

 mines their change in form ? Apparently that sumptuary 

 law which is a part of the machinery of natural selection. 

 If among adults, either by the development of weapons 

 or other means of protection from enemies, or by a change 

 in the environment suppressing enemies, the need for a 

 striped or spotted livery is past, then so surely will that 

 livery begin to degenerate ; and this because natural 

 selection no longer rewards, so to speak, those individuals 

 in which this or that livery is best developed : all the 

 members of the race, the defective as well as those which 

 have attained the maximum of perfection in this particular, 

 have an equal chance. It ceases to confer any benefits, 

 and thus in course of ages will gradually fade away. 



Since ancestral characters tend to reappear in the 

 young, the pattern now lost in the adult may well be pre- 

 served in the young : because any in which it is defective 

 will be killed out. In the case of the stripes in young 

 pigs, for example, as we have already pointed out, these 

 markings persist in the wild species, but they are wanting in 

 the domesticated races, where such a pattern is valueless. 



Similarly, the unseen hand of natural selection is no 

 less active in determining changes of pattern — the change 

 from a striped to a spotted livery. So long as stripes, 

 as such, conferred a benefit, so long did they maintain 

 their integrity. Any individual variations tending to 

 disturb the pattern were suppressed. 



But this same tendency to vary brings with it advan- 



