The Zoologist— April, 1873. 3471 



Firsth/. The cause assigned does not appear to be adequate. 

 The lawful proprietor, as I find, never fails to hatch the intruding 

 eg^, without the supposed resemblance, with undeviating uni- 

 formity. Nature's rule is success. Mr. Darwin, in his ' Descent 

 of Man' (vol. i. p. 79), under the head of" Moral Sense," speaks of 

 the "strong feeling of inward satisfaction" which impels "a bird 

 so full of activity to brood, day after day, over her eggs." With 

 some diffidence I venture to disagree with so great a naturalist. 

 There is no more inward satisfaction, in a moral sense, in a 

 brooding bird than in an eating or drinking bird. The desire to 

 sit is a burning, overwhelming one, which must be satisfied, like 

 that of hunger and thirst. There is no moral sense in it. It is 

 painful to the bird, which, as I have often seen, will sit on nothing 

 rather than not incubate. Hence I contend that the cause assigned 

 for the supposed resemblance of the eggs of the cuckoo to that of 

 other birds is not satisfactory. Birds are only too glad to sit on 

 the cuckoo's egg. 



Dr. Baldamus says, "There must be proportionably many ex- 

 ceptions" to the rule. Query, do not the exceptions become so 

 numerous as themselves to form the rule ? I have parted with 

 many of my specimens, 'but have still over sixty, which are with 

 the nests or eggs of sixteen or seventeen species. Of these in two 

 cases I do see a resemblance between the egg of Cuculus canorus 

 and the others. They are cases of Anthus pratensis and Motacilla 

 Yarrellii. But different persons view things variously, and an 

 advocate of the theory might see other resemblances. Dr. Rey's 

 list is compounded with great care, and I know what an amount of 

 trouble and skill must have been exerted to procure those data. 

 No doubt it tends to establish the theory. To be like the eggs of 

 the redstart {Phcenicnra ruticilla), the cuckoo must lay a blue egg, 

 to resemble those of C. arundinacea it should be green or greenish. 

 Such eggs have never come under my experience, so I can say 

 nothing regarding them, except that I have studied monstrous 

 specimens of eggs somewhat, and I observe that in the common 

 fowl, when one egg is found inside anoter, and both have shells, 

 as sometimes happens, the grain of the shell varies, though both 

 are the produce of the same hen. I mention this with reference 

 to the gigantic eggs named by Dr. Rey, and said to be those of 

 C. canorus of a blue colour. A blue and a green egg of C. canorus, 

 well authenticated, would do much to convert me. I do not affirm 



