354 GENERAL ZOOLOGY 



the left auricle, and thus they carry aerated blood almost 

 exclusively to the tissues of the body. In similar manner 

 when the impure blood from the right auricle enters the 

 ventricle most of it is forced directly into the pulmonary 

 artery, which carries it directly to the lungs. The nervous 

 system, especially the brain, is also more highly differen- 

 tiated than in the amphibians, and the bones are more com- 

 pletely ossified. In discussing the frog mention was made of 

 the fact that the skull moves on the first vertebra by two 

 rounded prominences called condyles. In the lizard and 

 other reptiles there is but a single condyle at the base of the 

 skull. A study of Fig. 180 will make clear the relation of the 

 most important organs. 



Development. The female pine lizard lays her eggs in the 

 ground, a short distance below the surface ; ten or fifteen 

 eggs are deposited in each lot. The eggs are elongated, from 

 14 to 18 mm. (a little over | in.) in length, and are roughened 

 on the surface, which causes dirt to adhere to them. They 

 increase in size as the embryo develops, finally hatching in 

 about two months. The young resemble the adult quite 

 closely in everything but size. They are able to take care 

 of themselves from the first. 



The Allies of the Pine Lizard : Reptilia 



Definition of Reptilia. The pine lizard will serve as an ex- 

 ample of the class Reptil'ia (Lat. repere, "creep"), which 

 includes also snakes, turtles, tortoises, alligators, crocodiles, 

 and many forms, the dinosaurs, for example, of which there 

 are no living examples. Reptiles are cold-blooded verte- 

 brates covered with scales or plates ; they breathe by lungs 

 throughout their life. A few reptiles are viviparous, but 

 most of them lay eggs, from which the young hatch in the 

 form of the adult. 



