50 



REPTILES 



plish this feat without undue difficulty. This reptile, a native 

 of South and Tropical Africa, and less than a yard in length, 

 is able to swallow a hen's egg, while specimens a foot in length 

 will " get outside " a pigeon's egg. The means by which this 

 is accomplished are simple and ingenious. The lower spines of 

 some of the vertebrae are so lengthened as to pierce the upper 

 side of the gullet, on the surface of which they appear as small 

 teeth-like knobs ; and when an egg is swallowed it is crushed 

 or sawn through by these projections. After the egg, with 

 some difficulty, is swallowed (the skin of the snake being dis- 



p IG . 3. — African Egg-eating Snake and its mode of swallowing food. 



tended almost to bursting), it gradually glides further and 

 further down till it comes to the projections in the gullet, when 

 the swollen part of the snake's neck suddenly resumes its 

 normal size ; and, after an interval, the broken shell is dis- 

 gorged. A similar structural peculiarity characterises an 

 Indian snake belonging to a different group, and known as 

 Elachistodon westermanni ; from which it has been suggested 

 that this species also displays egg-swallowing propensities. If 

 the suggestion be well-founded, we shall have an instance of 

 the independent development in two groups of an adaptation 

 to the same end. 



Monitor lizards ( Varanus) are likewise consumers of eggs, 



