CUCKOO. 307 



ally lays her eggs on the bare ground, sits on them, and 

 feeds her young.' 



In 'Nature' for November 18, .1869, Professor A. 

 Newton, F.R.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' eggs found in the nests 

 of different species of birds s * that the egg of the cuckoo 

 is approximately coloured and marked like those of the 

 bird in whose nest it is found,' 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 ' law of nature,' I must now declare that it is only 

 ' approximately,' and by no means universally true that tho 

 cuckoo's egg is coloured like those of the victims of her imposi- 

 tion, ike. 



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 



