INCUBATION WHILE STANDING 167 



Be that as it may, many existing birds make nests 

 no more elaborate than those of some reptiles ; the 

 practice of the Mound-builders in burying their 

 eggs is much the same as that followed by crocodiles 

 and tortoises, and the African or common crocodile 

 {Crocodilus niloticus) has been observed in Mada- 

 gascar sleeping on her deposit of eggs, and is be- 

 lieved to keep on hand to dig up the young v?hen 

 they hatch, and take them off. This is very like 

 the action of the Mound-birds — and also of those 

 fish which guard the nest, aerate the eggs, and pro- 

 tect the young — and as the crocodiles are the 

 nearest related of present-day reptiles to birds, as 

 their anatomy and bird-like eggs testify, it is 

 tempting to regard the Megapodes as the most 

 primitive of nesters, especially considering the 

 advanced state of their young on exclusion from the 

 egg. If, however, a previous coat of down is shed 

 in the shell, they are not so primitive as they look, 

 probably, but have gone back to the simple life. 



In any case, there are birds which do far less in 

 the way of nesting. The two giant Penguins, the 

 King (AptenodyUs pennantt) and the Emperor 

 (A. forsteri), for instance, do not put their single 

 egg down anywhere, but keep it pressed up against 

 the skin of the abdomen, which bulges ov*er it, and 

 supported by the feet, which are kept close together, 

 and so incubate standing. The bird thus cannot 

 walk freely, but it can shuffle about awkwardly, and 

 thus move its egg from-place to place if necessary. 

 The habit seems reasonable enough in the Empergr, 



