582 EEPTILIA [CH. 



the medulla oblongata, includes a longer portion of the spinal cord 

 than it does in Amphibia, for the hypoglossal nerve arises from 

 its side and escapes through an aperture in the exoccipital bone. 

 This nerve is reckoned the twelfth cranial, not the eleventh, for 

 there is a trunk called the spinal accessory or eleventh cranial, 

 which arises by several roots from the side of the medulla oblongata, 

 joins the vagus in a ganglion, and then leaving the skull supplies 

 some of the neck muscles. In the Ophidia this nerve is not dis- 

 tinguishable from the vagus. 



In the genital organs, the Lizards and Reptiles generally are 

 distinguished from Amphibia by the complete separation of the 

 mesonephros from the metanephros or functional part of the kidney. 

 The persisting part of the mesonephros, now known as the epididy- 

 mis, is only developed in the male, where it is closely connected 

 with the testis. As in the Newt it receives the vasa efferentia. In 

 the female the oviduct is shorter and has a wider internal funnel 

 than in the Amphibia, and it is also placed further back so as to 

 be rather nearer to the ovary. This is an arrangement suited to 

 the large size of the eggs, which are too heavy to be drawn any 

 distance by the current produced by the cilia of the oviduct. 



The egg is fertilised whilst still in the dviduct. The male lizard 

 has two organs called copulatory sacs or penes, situated, one on 

 each side, on the hinder wall of the cloaca. These, when not in 

 use, are hollow pouches opening into the cloaca. When in use they 

 are turned inside out, and are then seen to have grooves leading to 

 the openings of the vasa deferentia or archinephric ducts. 



Most Lizards lay their eggs in crevices amongst stones and 

 allow them to be hatched by the heat of the sun. In all cases a 

 considerable amount of development goes on before they are laid. 

 In the English species Lacerta vivipara the young burst through 

 the egg-shell and use up all the yolk whilst they are still in the 

 oviduct, so that in common parlance they are born alive, that is, 

 as little lizards and not as eggs. 



Order I. Rhynchocephala. 



As mentioned above, the order Rhynchocephala is represented 

 by the single species, Sphenodon punctatus, found only in New 

 Zealand. This is a very Lizard-like animal. The back is covered 

 with small scales which in the middle line form a comb-like crest : 

 the belly is covered with large square scales. In the skeleton and 



