Young Cuckoo's Habits. 249 



unfinished — a recurrence too weak to be efficient to 

 the ancestral habit. How could such an instinct 

 have been lost ? " To say that the cow-bird occa- 

 sionally dropped an egg in another bird's nest, and 

 that the young hatched from these occasional eggs 

 possessed some (hypothetical) advantage over those 

 hatched in the usual way, and that the parasitic habit 

 so became hereditary, supplanting the original one, 

 is an assertion without anything to support it, and 

 seems to exclude the agency of external conditions. 

 . . Again, the want of correspondence in the habits 

 of the young parasite and its foster-parents would, in 

 reality, be a disadvantage to the former. The un- 

 fitness would be as great in the eggs, and other 

 circumstances : for all the advantages the parasite 

 actually possesses in the comparative hardness of the 

 eggshell, rapid evolution of the young, etc., already 

 mentioned, must have been acquired, little by little, 

 through the slowly accumulating process of natural 

 selection, but subsequently to the formation of the 

 original parasitical inclination and habit." 



This precise argument lies, and is quite as efficient 

 as regards our own cuckoo. The young cuckoo shows 

 instincts wonderfully correspondent and answering to 

 the instinct or intention or plan of its real parents, 

 but little to that of its foster-parents : the young 

 cuckoo will hiss and dart at anyone coming near to 

 the nest, while the true young would have acted 

 quite differently. This is one illustration ; and, oddly 

 enough, it would seem that the conduct of the young 

 cuckoo is much the same whatever the nest he may 

 be in — the true young in which nests would behave 

 very differently. It would seem that the behaviour 



