412 Evolution and Adaptation 



animals at such times will trample and gore the distressed 

 one to death. In the case of wolves and other savage- 

 tempered carnivorous species the distressed fellow is fre- 

 quently torn to pieces and devoured on the spot." If any 

 one will be bold enough to claim in this case that this habit 

 has been acquired because of advantage to the pack, i.e. 

 if it be imagined that the pack gains more by feeding on 

 a weak member than by letting him take his chances of 

 recovery, it may be pointed out in reply that cattle also 

 destroy their weak or injured, but do not devour them, and 

 the same statement holds for birds, where the same instinct 

 has often been observed. Romanes has suggested that the 

 instinct of destroying the weak or injured members is of use 

 because such members are a source of danger to the rest of the 

 herd ; but Hudson points out that it is not so much the weak 

 and sickly members of the herd that are attacked in this 

 way, as those that are injured, and concludes, " the instinct 

 is not only useless, but actually detrimental." He suggests 

 that these "wild abnormal movements of social animals" are 

 a sort of aberration, so " that in turning against a distressed 

 fellow they oppose themselves to the law of being." Yet 

 whether we gain anything by calling this action aberrant or 

 abnormal, the important fact remains that it is a definite 

 response under certain external conditions, and is shown by 

 all the individuals of the species. 



The preceding illustrations of reactions that go to make 

 up the so-called instincts of animals may be separated into 

 those that are essential to the life of the individual or of the 

 race, those that are of some apparent use, although not 

 absolutely essential, and a few of no use at all, and fewer 

 still that appear to be even injurious. If the latter reactions 

 take place only rarely, as appears often to be the case, 

 they are not sufficiently harmful to cause the destruction of 

 the race. The evidence points to the conclusion, I believe, 

 that the origin of these tropisms and instincts cannot be 



