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, ze. 
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 
