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One of the most striking of these, perhaps, is that of a 

 species of sloth which hangs and browses upon the trees in 

 Central and Southern America. These trees are festooned with 

 great masses of pendant moss which cling closely round branches 

 and stumps of branches cominsr out from the larger trunks. 

 Some naturalists remarked that although these sloths are of the 

 same green colour as certain masses of tree moss, they appear to 

 be rendered conspicuous by a large brown mark upon the back. 

 This, however, is only when the sloth is removed from its natural 

 environment, for it is found that when they are at home upon the 

 trees, the brown patch upon the back gives an almost exact 

 imitation of a stump of a broken branch. 



Our common ground animals, such as rabbits, weasels, and 

 field mice, are usually of the iame neutral colour as the half dry 

 grass and leaves among which they hide themselves. The 

 dappled skins of fallow deer so exactly resemble the appearance 

 of light falling through a chequered curtain of leaves upon the 

 ground, that it is often difiicult to observe them. The stripes on 

 the tiger so resemble the grass and the shadows between of the 

 tropical jungle, that even the most experienced eyes are constantly 

 deceived. Spotted leopards and tiger cats which inhabit the 

 woocK may hide with impunity among foliage where any large 

 animal of uniform colour would be rendered conspicuous. 



But all this is not protective mimicry in the sense in which 

 the term is used by naturalists. We speak of such cases as 

 instances of protective resemblance, and I wish to draw, at the 

 outset, a clear distinction between this and protective mimicry, 

 because the origin of the two methods of obtaining protection 

 from enemies are radically different. The term protective mimi- 

 cry is only applicable when applied to instances in which one 

 living creature so strikingly resembles another of a different 

 species as to be readily mistaken for it. Protective mimicry 

 differs from protective resemblance to surroundings in that it is 

 based upon the desire to be conspicuous, and not upon the desire 

 to be inconspicuous. Now, let me say before I go further that, 

 in using woids and phrases such as "mimicry," "desire to be 

 inconspicuous," and so on, the naturalist does not mean that 

 these humble fellow creatures of ours make any endeavour, 

 either conscious or unconscious, to be like their neighb( urs. It 

 would be perfectly futile if they did. If we rational folk by 

 taking thought cannot add one cubit to our stature, still 

 less is it likely that a butterfly could voluntarily make itself like 

 a wasp, or a spider like an ant or a beetle. The phenomena 

 with which we are dealing are merely the outcome of natura^ 



