216 THE BOOK OF A NATURALIST 
That, for example, of the young cuckoo ejecting 
its foster-brothers from the nest; of slave-making 
ants, and of the larvae of the Ichneumonidae feeding 
on the live tissues of the caterpillars in whose bodies 
they have been hatched. He said that it was not 
perhaps a logical conclusion, but it seemed to him 
more satisfactory to regard such things “not as 
specially endowed or created instincts, but as small 
consequences of one general law”—the law of 
variation and the survival of the fittest. 
