492 LACERTILIA 



to mere vestiges. Moreover in some of these burrowing and 

 limbless forms the quadrate bones have become more or less 

 immovable. 



We divide the Autosauri into three sub-orders : — I. Geckones, 

 p. 502; II. Laceetae, p. 513; III. Chamaeleontes, p. 567, 

 with about 270, 1500, and 50 species respectively. 



The Autosauri are of great interest, since they exhibit a 

 great, almost endless variety in shajpe, size, and structure in 

 direct adaptation to their surroundings. Most of these modiii- 

 cations are restricted to the external organs, or rather to those 

 which come into direct contact with the outer world, namely the 

 skin, the limbs, the tail, or the tongue. The majority of the 

 Autosauri are terrestrial, but there are also semi-aquatic forms. 

 There are climbing, swiftly running, and even flying forms, 

 while others lead a subterranean life like earthworms. Most 

 of them live on animal food, varying from tiny insects and 

 worms to Birds and Mammals, while others live upon vegetable 

 diet. According to this diet, the teeth and the whole digestive 

 tract are modified. The intestine is relatively short in the 

 carnivorous, long in the herbivorous species. But swiftness, 

 the apparatus necessary for climbing, running, and digging, the 

 mechanism of the tongue, the armament and the muscles of the 

 jaws (hence modifications of the cranial arches, etc.), stand also 

 in correlation with the kind of food and with the way in which 

 it has to be procured. 



A very interesting study of the influence of the climate and 

 the nature of the country upon Eeptiles has been made by 

 Boettger^ with especial reference to the Transcaspian desert- 

 region. The winter is there short, but very severe, and there is a 

 considerable amount of snowfall, while the summer is intolerably 

 hot. The spring arrives suddenly. Lilies and tulips, which 

 have been asleep for nine or ten months, sprout towards the 

 end of February, and a carpet of flowers covers the ground 

 for a short time. Then everything shrivels up during the 

 rainless and fierce heat of the summer, and the autumnal storms 

 of dust and sand kill off the last remnants of vegetation. There 

 are no trees, and even prickly shrubs are rare. Instead of broad 

 leaves the plants have grass-like blades or needles. The little 

 shrubs do not form coherent patches, but they are scattered 



1 Zool. Gart. 1889, p. 1. 



