scarlet, yellow, and black (colored Fig. 6) of the same tints, and it is hardly distinguishable from the harlequin. The coral snake is said to mimic the harlequin snake. It also imitates the quiet inoffensive habits of the harlequin snake, which fortunately does not strike except under the greatest provocation. The rattles of the less poisonous and seldom fatal 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.
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Fig. 279.—Gila Monster (Heloderma suspectum), of Arizona. If poisonous, 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).
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Fig. 280.—Chameleon (Anolis), or green lizard of southern U.S. Far excels European chameleon (Fig. 281) and all known animals in power of changing color (green, gray, yellow, bronze, and black).
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 exactly like their parents. The first fact gives stability, the second makes
