markings are all yellow, and mainly in the form of smallish circular spots, 

 which are scattered over the whole black carapace as well as over the fleshy 

 parts. On the head and neck and fore-legs some of them are lengthened out 

 into streaks. The plastron is buff-colored, but marked with big, irregular black 

 blotches — a pattern and coloration highly characteristic of the small American 

 tortoises. The obliterative effect of the circular bright-yellow spots is much 

 the same as that of the Painted Tortoise's richer pattern ; but the little yellow 

 disks are more aptly suggestive of spots of sunlight on dim brook-bottoms. 



To sum up the foregoing fragmentary account of chelonian coloration: 

 Most turtles, aquatic and terrestrial, are obliteratively shaded, and, in a gen- 

 eral way, obliteratively colored; but comparatively few of them have highly 

 specialized obliterative picture-patterns. 



We now come to Amphibians, the last of the vertebrate classes we have 

 to consider. These, unlike tortoises, are for the most part soft, weak-skinned 

 animals, living much exposed to danger, and being much preyed on by ra- 

 pacious creatures. Accordingly, their disguising coloration has been highly 

 and variously developed. Most variously, indeed, as their habits are ex- 

 tremely various ; yet the principles we have already studied cover all the vari- 

 ations. In their larval state, as "polliwogs," "tadpoles," etc., these animals 

 are all more or less fish-like, both in habits and appearance, and their oblit- 

 erative coloration does not then differ essentially from that of certain mud 

 fishes (Chapter XXIII, p. 169). But in the perfect state the various types 

 become highly differentiated both from other animals and from one another. 

 How many and diverse, for instance, especially as regards disguising-colora- 

 tion, are the types of frog and toad! Even if we confine ourselves to those 

 of temperate North America and Europe (as we, personally, are obliged to 

 do, because of our ignorance of the no doubt far more diversely specialized ' 

 tropical forms), the essentially different types are many. First, there are 

 the aquatic frogs, as the common Green Frog and the great Bullfrog of North 

 America (Rana clamitans and R. catesbiana), etc. Then the terrestrial wood- 

 land frogs (Rana sylvatica, etc.), colored like some delicate forest ground- 



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