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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 6 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 
hypothesis 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 
