REPTILIA 



147 



scarlet, yellow, and black (coloured Fig. 6) of the same tints, 

 and it is hardly distinguishable from the harlequin. The 



Fig. 279. — Gila Monster (Heloderma suspectum) , of Arizona. Ifpoisonous.it 

 is the only instance among lizards. It is heavy-built, orange and black mottled, 

 and about 16 inches long. Compare it with the green lizard (Fig. 280). 



scarlet snake is said to mimic the 

 imitates the quiet inoffensive hab- 

 its of the harlequin snake, which 

 fortunately does not strike except 

 under the greatest provocation. 

 The rattles of the less poisonous 



but deadly rattlesnake (Fig. 

 272) may be classed as an 

 example of warning sound which 

 most animals are quick to heed 

 and thus avoid encounters which 

 might be destructive to either the 

 snake or its enemy. 



Survival of the Fittest. — The two 

 facts of most far-reaching importance 

 in the history of animals and plants 

 are: (1) Heredity; animals inherit 

 the characteristics of their parents. 

 (2) Variation; animals are not ex- 

 actly like their parents. The first 

 fact gives stability, the second makes 



harlequin snake. It also 



Fig. 280. — Chameleon (Ano- 

 lis), or green lizard of south- 

 ern U.S. Far excels European 

 chameleon (Fig. 281) and all 

 known animals in power of 

 changing colour (green, gray, 

 yellow, bronze, and black). 



