DESCRIPTION OF A LIZARD. 569 



and Iguanas, long and terminally clubbed in Chamaleons, is 

 oftenest a narrow bifid organ of touch. The opening of the 

 cloaca is transverse. There is a urinary bladder, corre- 

 sponding to that of the frog, and a double penis. Most are 

 oviparous, but in a few the eggs are hatched within the body. 

 They are usually active, agile animals, beautifully and often 

 protectively coloured. The caudal region is often very brittle; 

 lost tails and even legs may be regenerated. The food 

 generally consists of insects, worms, and other small animals, 

 but some prey upon larger animals, and others are vegetarian. 

 Most are terrestrial, some arboreal, a few semi-aquatic, and 

 there is one marine form. Lizards are most abundant in 

 the tropics, and are absent from very cold regions, 



^^Description of a Lizard as a type of Reptiles. 



The following description applies especially to the long- 

 tailed green lizard {Lacerta viridis), found abundantly in 

 Jersey, but, except in minor points, it will be found to apply 

 equally to the small British grey lizard (Lacerta agilis) and 

 to the viviparous lizard (Zootoca vivipara) : — 



Form and external features. — The depressed head is 

 separated from the body by a distinct neck, but the 

 posterior region of the body passes gradually into the long 

 tail, which is often mutilated in captured specimens. Both 

 fore- and hind-limbs are present, and both are furnished 

 with five clawed digits. Of the apertures of the body, the 

 large mouth is terminal, the external nares are close to the 

 end of the snout, and the cloacal aperture is a considerable 

 transverse opening placed at the root of the tail. There is 

 no external ear, but the tympanic membrane at either side 

 is slightly depressed below the level of the skin of the head. 

 The eyes are furnished with both upper and lower eyelids, 

 and also with a nictitating membrane. 



Skin. — As contrasted with that of the frog, the skin is 

 remarkable as possessing a distinct exoskeleton of epidermic 

 scales. In the head region these exhibit a definite arrange- 

 ment characteristic of the species. With the presence of 

 an exoskeleton we must associate the absence of the 

 numerous cutaneous glands of the frog ; these are here 

 represented only by a row of "femoral glands," which open 



