May 



conveyance generally. It is not primarily due to any 

 depth of gape, exceptional as this may be, that the 

 cuckoo is able to convey its egg in its bill ; but to 

 the fact that the egg itself is abnormally undersized. / 

 A cuckoo's egg in my possession measures 0*94 by 

 0^69 inch ; whilst four eggs of a pied- wagtail, with 

 which it was found, gave an average of 0*84 by 0*63 

 inch. The relative smallness of the cuckoo's egg 

 will be apparent from the fact that the cuckoo 

 measures thirteen and a half inches from beak to 

 tail, and the pied-wagtail seven and a half inches. 

 'This fact is the more significant because the nor- 

 mally non-parasitic American cuckoo lays a full- 

 sized egg. 



It would appear that the cuckoo is under some 

 physiological or anatomical disability preventing it 

 from laying a full-sized egg ; and, just as the small- 

 ness of the egg suggests such peculiarities in the 

 bird laying it, so does it augur physiological or 

 anatomical peculiarities in the young hatched under 

 such straitened circumstances. It is probably due to 

 the fact that the embryo is packed away in about a 

 fourth of the space to which a chick with the makings 

 of a cuckoo in him is entitled, and to the limited 

 amount of nutriment contained in so small a com- 

 pass, that the young cuckoo hatches out early from 

 his uncomfortable quarters with a certain leeway to 

 make up in the matter of diet and elbow-room. Is 

 the anomalous structural peculiarity in the back of 

 the young cuckoo due to the obstruction to free 



