122 Transactioyis.—Zooloijy. 



Canary, but is more elliptical in shape — I should call it ovoido- 

 elliptical — and its length is 0-94 in., and its breadth 0-7 in. I 

 liave requested the Messrs. Ross, if another egg is found, ta 

 allow it to hatch out and in this way positively settle the 

 identity of the egg. I think it likely that many of the eggs are 

 hatched by Orthonyx and Anthornis, and very soon the young 

 bird crawls from the nest, to be still fed by its foster-parents, 

 Gerygone or any other kind-hearted strangers. The egg is 

 quite near enough in appearance to that of the Canary to be 

 easily overlooked in most clutches of eggs of that little bird. 

 It may be objected that this egg differs markedly from the 

 specimens before discovered, but I think you will agree with 

 ine presently that that is no reason for our doubting its 

 identity. In the first place, nearly all species of birds at one 

 time or other produce eggs differing markedly from the normal 

 in size and colouring. For instance, I have some specimens 

 of pure -white eggs of Anthornis and of Prosthemadera ; 

 also in my series of eggs of the little Tomtit much varia- 

 tion occurs, but that is not a point I am about to rely 

 on. My opinion is that this is another instance of that 

 wonderful power in nature of producing "protective resem- 

 blance." We all know the difficulty in finding the eggs of 

 the Tern among the pebbles of the river-beds ; and the eggs 

 of the Dotterel (Charadrius hwinctns) are similarly pro- 

 tected. The eggs of the Ground-lark (Anthus nova-zca- 

 landicb) much approach in colour the dusty earth around 

 the depression in which they lie, and it is almost impossible 

 for them to be refound if once lost sight of amidst the dried 

 tussocks and grass around. The same species of Gull lays 

 eggs which differ markedly in ground-colour and blotches 

 according to the part of the beach or to the character of 

 the debris and stones among which they lie(26). 



The extraordinary difi'erence between the eggs of the two 

 species of Chalcococcyx, lucidus and basalis, has excited much 

 comment, but can, I think, be accounted for in the same way. 

 As we find among the New World Cuckoos several which 

 build their own nests and hatch their own delicate green 

 eggs, let us assume that this is the original natural colour of 

 many of these species. Now, I do not know of very many 

 birds which lay eggs like tliis, and it may come about, assum- 

 ing the habit of parasitism to have been first established, that 

 these birds must get their eggs into nests whei'e the wrong 

 colouring will not be noticed, or where the bird is so easily 

 duped as not to object to the peculiar appearance of the 

 strange egg(27). Such dupes do occur, as, for example, the 

 Common Hedge-sparrow will brood with complacency the egg 

 of tlie Redbreast [Erythracus rubecula), so unlike her own 

 that for all we know to the contrary she may be colour- 



