10 THE STORY OF REPTILE LIFE. 



thereof, and of the heavens above, many exceed- 

 ing in stature all creatures that have ever lived 

 either before or since. Waxing numerous they 

 branched out into many tribes, each carving a 

 way for itself. What the members of these 

 several tribes were like, and how they have 

 overcome their enemies ; what weapons they 

 have employed ; what subterfuges they have re- 

 sorted to ; how they have conducted themselves 

 as parents ; and what their pedigrees disclose, is 

 to be the theme of the following chapters. 



But before w^e proceed further, it is essential 

 that a clear idea should be formed of what con- 

 stitutes a reptile. Save among experienced 

 naturalists, only the very vaguest notions appear 

 to exist on this head. Generally, a group of 

 animals totally distinct is included in the popular 

 idea of the class reptiles. These alien forms are 

 the frogs and toads, newts and salamanders. 

 Now between the reptile and the creatures just 

 referred to there is a very wide difference. Both 

 agree in being "cold-blooded," in having a back- 

 bone, and four limbs adapted for walking : but 

 they differ fundamentally in that the young of 

 the frog-tribe certain peculiar exceptions apart 

 when they leave the egg do so in the form 

 of "larvae." That is to say they differ from 

 their parents in that they are obliged to live in 

 water and to breathe by means of gills like the 

 fishes. Later, these gills disappear and breathing 

 by lungs is substituted. But in this adult stage 

 they still differ from the reptile in that the skin 

 is naked, and richly supplied with glands for the 

 purpose of keeping the skin moist hence the 



