LACERTILIA. 



847 



is no tympanum the extracolumellar cartilage is attached to the 

 inner side of the quadrate. 



In the vascular system there are a smus venosus, a single 

 ventricle with an incomplete septum, and three pairs of arterial 

 arches wdth a ductus Botalli between the carotid and systemic 

 arches (except in the Varanidae). The subclavians are given 

 off separately or together by the right arch. The visceral arteries 

 arise from the dorsal aorta. The anterior abdominal vein is 

 unpaired and does not anastomose with the iliac and caudal 

 veins. 



Fat bodies between the skin and ventral abdominal muscles 

 are often present. They are largest in the spring at the time of 

 propagation. 



The kidneys are placed in the posterior part of the body- 

 cavity, and are covered on the ventral side only by peritoneum. 

 They are more or less lobed, are sometimes united with one 

 another and may extend into the caudal region. A cloaeal 

 bladder is present. 



The testes are oval bodies placed further forwards than the 

 kidneys (Fig. 191). The ureter usually joms the vas deferens 

 of its side and the two open by one openmg into the lateral part 

 of the cloaca. The oviducts have the usual arrangement. 



There are two penes. They have the form of eversible hollow 

 sacs opening into the posterior wall of the cloaca, and attached 

 by a retractor muscle, passing from their hinder end, to some 

 of the caudal vertebrae. A groove runs to them from the open- 

 ing of the vas deferens for the conveyance of sperm. Erectile 

 tissue is foimd in thek walls. These organs can be everted 

 through the anus and used as copulatory organs. They are 

 present in both sexes, though less developed in the female than in 

 the male. 



Most lizards lay eggs, but a few are viviparous {Lacerta vivi- 

 para, Anguis fragilis, Seps, Chamaeleon). In some cases the eggs 

 are retained for a part of the development and the young are 

 hatched at a greater or less period after laying. The shell is 

 usually leathery, but may be hard. Most of them are harmless, 

 and are useful by destroying insects. Larger species, as the 

 Iguana, are hunted for the sake of their flesh. By far the greater 

 number and all the larger and more beautifully coloured species 

 inhabit the warmer and hot countries. 



