PINE-LIZARD AND ITS ALLIES: REPTILIA 351 



auricle, with some admixture of venous blood, is driven to 

 the arterial branches supplying the head and body generally. 

 The nervous system, especially the brain, is also more highly 

 differentiated than in the amphibians, and the bones are more 

 completely ossified. A skeletal difference is the articulation 

 of the cranium to the first vertebra by means of a single con- 

 dyle. A study of Fig. 176 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 oblong in shape, 

 from fourteen to eighteen millimeters (a little over half an 

 inch) in length, and are roughened on the surface, causing 

 dirt to adhere to them. One lot brought to an observer in 

 North Carolina late in the month of June had been plowed 

 up. The eggs increased in size as the embryo developed, 

 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 

 example of the class Reptil'ia (Lat. repere, to creep), which 

 includes also snakes, turtles, tortoises, alligators, and croco- 

 diles. Reptiles are cold-blooded vertebrates 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. 



Four out of the five groups into which the class may be 

 divided, are here considered. 



Lizards. Most of the Lacertil'ia (Lat. lacerta, a lizard) are, 

 like the pine-lizard, elongate reptiles with four limbs and 

 movable eyelids. A few families have, however, lost one or 



