bird; then the semi -terrestrial grass-haunting frogs {Rana palustris, Rana 

 virescens, etc.). Then, again, the terrestrial toads, aquatic only during the 

 breeding season, and otherwise fitted for life on and under comparatively 

 dry and open ground; then the little, tight-folding tree toads {Hyla, etc.), 

 modified both in form and color for concealment on perpendicular reed-stems, 

 on sticks and twigs, or on tree trunks and on rocks, as the case may be. The 

 Common Tree Toad {Hyla versicolor) of eastern North America, is a good 

 t5^e of this remarkable group. It is a tree-bark haunter, veritably moth-like 

 in the exquisite minuteness and accuracy of its tree-bark pattern, and gifted 

 in a high degree — as many amphibians are in less degrees — with 'chame- 

 leonic ' powers of rapid color-change. 



Different as are the various batrachian types above named, both in habits 

 and in superficial aspect, they all have much in common even in their color- 

 ation. For they are all obliteratively shaded, delicately and fully, and the 

 concealment of all of them depends primarily on this same great principle. 

 Those which cling to tree trunks are, of course, lighted as are woodpeckers and 

 other scansorial birds (Chapter VIII) — that is, almost like the ground ani- 

 mals — and hence are similarly counter shaded. The little reed-toads and 

 twig-toads, folded up tight and smooth and narrow, and clinging close to 

 the tree-branch or reed-stem, are likewise 'blended into' the surface of their 

 perch by aid of their obliterative shading. But of course this is the case 

 only when they are seen in back view. In profile, they may still be and often 

 are 'obliterated,' being indistinguishable from whatever forms their back- 

 ground; but their lack of markings (a trait characteristic of some kinds, par- 

 ticularly green ones) hinders this effect, and must often cause their contours, 

 thus relieving, to be visible. Here mimicry comes into play; for their bodies 

 are so modified in form, and held in such positions, as readily to pass for 

 mere slight excrescences of the plant-surfaces on which they are sitting. There 

 may even be species whose whole disguising equipment is thus mimetic, 

 to the exclusion of obliterative shading. But, with or without these 

 possible few exceptions, the protective coloration of batrachians is preem- 



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