LIZARDS. 577 



The light reproductive organ tends to lie larger and in front of the 

 left. In many of the males, the Wolffian body is well developed. 

 Viviparous, or what is clumsily called ovo-viviparous, parturition is 

 well illustrated by Zootoca vivipariis, Anguis fragilis, Seps, &c., but 

 most lay eggs with more or less calcareous shells. In Trachydosaurus 

 and Cydodus the embryo seems to absorb food from the wall of the 

 uterus. It is likely that Laeertilians existed in Permian ages, but their 

 remains are not numerous before the Tertiary strata. 



Many instructive illustrations of evolutionary change are afi'orded by 

 lizards. Thus there are numerous gradations in the reduction of the 

 limbs, from a decrease in the toes to entire absence of limbs. The 

 diverse forms of tongue and the varied positions of the teeth are also 

 connected by gradations. From the variations of the wall lizard [Lacerta 

 i/niralis), Eimer elaborated most of his theory of evolution. 



Soiiii; Families of Laccrtilia. 



The class includes great variety of form. 



In the Geckos {Geckonid;ie) the vertebrLX? are biconcave or amphi- 

 ca?lous, the tongue is short and fleshy, the eyelids are rudimentary, the 

 teeth are pleuroclont, the toes bear numerous plaits, by means of which 

 they adhere to smooth surfaces. The Geckos have been observed to eat 

 their own young and even their own tails. The name Gecko indicates 

 their call. Examples : — rialydaclyUis niaurita!n\-iis{S. Europe), Hcini- 

 dtiityiits in most warm countries, Piychozooii^ \\'ith lateral webs of skin 

 which ser\'e as parachutes. 



The Agamas (^VgamidL\3) are acrodont lizards common in the eastern 

 hemisphere. Examples: — Agai/ia ; Draco, \\\i\\ the skin extended on 

 long prolongations of five or six posterior ribs ; CiihiniydosaKriis, an 

 Australian lizard, with a large scaled frill around the neck ; IMoloch, 

 another Australian form bristling with sharp spikes. 



The Iguanas (IguaniiKv) are pleuroilont lizards, represented in the 

 warmer parts of the New World. Examples : — Iguana, an arboreal 

 lizartl, with a large ilistensible de\\lap ; AinhiyrJiyiuIius or OroocLp/ia/ns 

 iTistaius,:\ marine lizard confined to the Clalapagos Islands ; Basiiistiis, 

 in S. Mexico, with none o{ the marvellous cjualities i^f the m)tho- 

 logical basilisk ; Ano/is, the American chamivleon, \\ith powers of 

 rapid colour change ; PJirynosoina, the American "horned toad," with 

 munerous horny scales, antl a collar of sharp spines suggesting in 

 miniature that of some of the extinct Reptiles. 



The slow NNorms (.\nguid;v), are limbless lizards, with serpentine 

 body, long tail, rutlimentary girdles and sternum. The British species, 

 Atigiiis fragilis, is neither blind nor poisonous ; the tail breaks very 

 readily ; the young are hatched within the mother. The American 

 " glass snake '' — Opiicosatinis Vi-iitralis — is in many ways like our sknv 

 worm. 



The poisonous Mexican lizard (Hclodenna siispciiuin) measures over 

 a foot in length, and is covered with bead-like scales. Its bite is 

 poisonous, antl rapitUy fatal to sniall Mammals. It is interesting to 

 find poisonous powers like those of many serpents exhibited b)' this ex- 

 ceptional lizard. 



The water lizards (Varanida) are large semi-aquatic forms of carni- 



