CUCKOO. 
307 
ally lays her eggs on the bare ground, sits on them, and 
feeds her young. 5 
In 4 Nature 5 for November 18, 1869, Professor A. 
Newton, F.K.S., has published an article on a somewhat 
obscure point connected with the instincts of the cuckoo. 
He says that Dr. Baldamus has satisfied him, by an exhibi- 
tion of sixteen specimens of cuckoos 5 eggs found in the nests 
of different species of birds., ‘ that the egg of the cuckoo 
is approximately coloured and marked like those of the 
bird in whose nest it is found, 5 for the purpose, no doubt, 
of deceiving the foster-parents. Professor Newton adds, 
however : — 
Having said this much, and believing as I do the Doctor to 
be partly justified in the carefully worded enunciation of what 
he calls a 4 law of nature/ I must now declare that it is only 
‘ approximately/ and by no means universally true that the 
cuckoo’s egg is coloured like those of the victims of her imposi- 
tion, &c. 
Still, when so great an authority as Professor Newton 
expresses himself satisfied that there is a marked tendency 
to such imitation, which in some cases leads to extra- 
ordinary variations in the colouring of the cuckoo’s egg, 
the alleged fact becomes one which demands notice. The 
question, of course, immediately arises, How is it conceiv- 
able that the fact, if it is a fact, can be explained ? We 
cannot imagine the cuckoo to be able consciously to colour 
her egg during its formation in order to imitate the eggs 
among which she is about to lay it ; nor can we suppose 
that having laid an egg and observed its colouring, she 
then carries it to the nest of the bird whose eggs it most 
resembles. Professor Newton suggests another theory, 
which he seems to think sufficient, but which I confess 
seems to me little more satisfactory than the impossible 
theories just stated. He says : — 
Only one explanation of the process can, to my mind, be 
offered. Every person who has studied the habits of birds with 
sufficient attention will be conversant with the tendency which 
certain of those habits have to become hereditary. It is, I am 
sure, no violent hypothesis to suppose that there is a very 
reasonable probability of each cuckoo most commonly placing 
