Mimicry, in the sense of the counterfeiting of single inanimate things, seems 

 to play but a very smaU part in the coloration of snakes and lizards, whose 

 disguising costumes are almost always obliierative, purely and simply. In fact, 

 we do not know any positive cases of such mimetic equipment among reptiles, 

 beyond the fragmentary sort mentioned in connection with the Green Snake. 



Crocodilians — that is to say, crocodiles, alligators, and gavials — ^have not 

 very highly specialized protective coloration. Mud-colored, armored, and 

 unmarked, — comparatively speaking — they yet have counter shading, which 

 tends to 'obliterate' them, in the water and on land. Often, however, they are 

 so placed as not to be 'obliterated,' but plainly to show their great, hulking 

 forms. Then their irregular, lumpy outlines often serve to make them pass 

 for logs or stones. Unquestionably, they often present, either wholly or in 

 part, a mimetic resemblance to such objects. An alligator swimming or rest- 

 ing at the surface shows above water only his snout, his eyes, and sometimes a 

 portion of his back — three or four gray-brown lumps which look, to any but the 

 most experienced eye, like points of rock, or projections of a submerged log — 

 ■or cypress "knees." However casual, all such resemblances must be of service 

 to the alligator.* Such an animal's more or less mimetic likeness to his inani- 

 mate surroundings is often increased by the sticking to his heavy, muddy back 

 and sides, when they are out of water, of bits of vegetable rubbish. This is 

 the case also with some of the great fresh-water tortoises, whose concealing- 

 coloration is at least as simple as the crocodilians. These tortoises even have 

 algae and various mosslike, lowly water-plants growing on their shells, and 

 some have dermal appendages which look like such plant-growths. For the 

 rest, they are obliteratively shaded, and more or less mud-colored. The gigan- 

 tic land tortoises, such as those of the Galapagos Islands, have even less to 

 show in the way of protective coloration. With no obliterative shading worth 

 mentioning, and no markings, they wear, it would seem, merely the simple, 

 organic colors of old, weather-beaten shells and wrinkled hides. Fruit- 



* In furtherance of offensive operations. For the brutes are the kings of the waters they inhabit, 

 and have — at least when they are full grown — scarcely any predaceous enemies. 



176 



