308 ANIMAL INTELLIGENCE. 



her eggs in the nest of the same bird, and of this habit being 

 transmitted to her posterity. 



Now it will be seen that it requires but only an application 

 to this case of the principle of ' natural selection/ or ' survival 

 of the fittest,' to show that if my argument be sound, nothing 

 can be more likely than that, in the course of time, that prin- 

 ciple should operate so as to produce the facts asserted, the eggs 

 which best imitated those of particular foster-parents having 

 the best chance of duping the latter, and so of being hatched 

 out. 



Now, granting to this hypothesis the assumption that 

 individual cuckoos have special predilections as to the 

 species in whose nests they are to lay their eggs, and that 

 some of these species require to be deceived by imitative 

 colouring of the egg to prevent their tilting it out, there 

 is still an enormous difficulty to be met. Supposing that 

 one cuckoo out of a hundred happens to lay eggs suffi- 

 ciently like those of the North African magpies (a species 

 alluded to by Professor Newton) to deceive the latter into 

 supposing the egg to be one of their own. This I cannot 

 think is too small a proportion to assume, seeing that, ex 

 hypothesi, the resemblance must be tolerably close, and 

 that the egg of the magpie does not resemble the great 

 majority of eggs of the cuckoo. Now, in order to sustain 

 the theory, we must suppose that the particular cuckoo 

 which happens to have the peculiarity of laying eggs so 

 closely resembling those of the magpie, must also happen 

 to have the peculiarity of desiring to lay its eggs in the 

 nest of a magpie. The conjunction of these two pecu- 

 liarities would, I should think, at a moderate estimate 

 reduce the chances of an approximately coloured egg being 

 laid in the appropriate nest to at least one thousand to 

 one. But supposing the happy accident to have taken 

 place, we have next to suppose that the peculiarity of 

 laying these exceptionably coloured eggs is not only con- 

 stant for the same individual cuckoo, but is inherited by 

 innumerable generations of her progeny; and, what is 

 much more difficult to grant, that the fancy for laying 

 eggs in the nest of a magpie is similarly inherited. I 

 think, therefore, notwithstanding Professor Newton's strong 

 opinion upon the subject, that the ingenious hypothesis 



I 



