142 THE STORY OF REPTILE LIFE. 



of the nest is wider than the top, and has its 

 centre in the form of a mound. Thus, when 

 the eggs, some twenty to thirty in number, are 

 laid, they roll down the slope into the circular 

 trench. When the hole is filled up the mother 

 takes up her station on top when sleeping, and 

 thus betrays what she had taken so much pains 

 to conceal. In about twelve weeks the eggs are 

 hatched. The mother, when the time of hatching 

 is at hand, repairs to the nest to liberate her 

 young ones and conduct them to the water. The 

 reality of the mother's regard for her young was 

 proved by the naturalist Yoeltzkow, who built 

 a fence about a nest near hatching time. Several 

 times she returned and partly destroyed it during 

 the night, and each time it was replaced by a 

 stronger. At last the nest was found deserted, 

 and then it was discovered that the mother had 

 dug a hole beneath the fence through which her 

 offspring escaped. 



It seems that the mother is warned of the 

 approaching escape from the shell by a peculiar 

 hiccough-like noise made by the young when she 

 returns for her nightly slumbers. Young birds, 

 it will be remembered, also signal their approach- 

 ing appearance by " cheeping " whilst within the 

 shell. Like the birds, the Crocodile breaks the 

 shell by means of an egg-tooth placed on the top 

 of the snout. The nest of the Alligator (Alli- 

 gator missisippiensis) is a much more portentous 

 structure, resembling that of the mound birds. 

 It is a large structure, built by the female, and 

 formed of dead leaves and twigs, together with 

 fine earth heaped up into a mound about three 



