REPTILIA 211 



of a tadpole. To make one lie quiet on a glass slip with a 

 cover glass over its tail, immerse it in the chloretone mix- 

 ture (water one part and one per cent chloretone five parts) 

 until completely unconscious. A drop of blood put on a 

 clean glass slip and at once spread very thin by drawing 

 the end of another glass slip lightly over it will show the 

 oval nucleated red corpuscles characteristic of most of 

 the vertebrates except mammals. 



The brain with its ten pairs of nerves joining its ventral 

 aspect may be seen by cutting away the roof and sides of 

 the skull with a heavy knife. Any one wishing to study 

 the skeleton can render the flesh easily removable by boil- 

 ing the animal an hour or more, depending upon its age, 

 in two quarts of water containing an ounce of soap cut into 

 slices. 



17. REPTILIA 



The reptiles are distinguished from the amphibians by 

 the presence of scales and the fact that the young never 

 breathe by gills. Only three orders inhabit this country. 

 They are the Squamata (snakes and lizards), the Chelonia 

 (turtles and tortoises), and the Crocodilia (crocodiles and 

 alligators. 



Squamata: Lizards and Snakes 



The name of this order is derived from the Latin squama, 

 a scale. The distinguishing feature of the group is the 

 presence of horny epidermal scales covering the surface. 



The Lizards. More than eighty species of lizards are 

 known in North America. They differ from the snakes 



