ing fishes as may come into his hands is the key to a new and strangely beau- 

 tiful realm of natural scenery, which must otherwise have remained almost 

 wholly unknown to him. For there can be no reason to doubt that the oblit- 

 eratively shaded bodies of these fishes are covered with true pictures of their 

 mysterious natural environment, so far withdrawn from human ken. Pos- 

 sibly these pictures never reach quite so fine a point of minute specialization 

 as do the best of those worn by birds and butterflies, for water obstructs 

 sight as air does not, and the eyes of subaquatic creatures are probably cruder 

 (?) organs than those of the higher land animals. Nevertheless, it is evident 

 that the predaceous fishes and other subaquatic animals see keenly, after a 

 fashion, and also that this fashion is not so widely different from our own, 

 because in all cases where we are able to compare the pattern of a highly 

 marked subaquatic creature with that of its natural environment, we find a 

 beautifully true and finely detailed correspondence between the two. From 

 these accessible cases alone one might plausibly infer that all highly patterned 

 fishes wear real background-pictures. But to a person with artistic sight 

 (i. e., sight highly and truly and roundedly developed), and an understanding 

 of obliterative coloration, a glance at any such fish far removed from its home 

 will leave no doubt on that score, even though the exact nature of the fish's 

 normal environment remains unknown. Perhaps the most familiar among 

 the ' ground '-haunting fishes that are not quite inaccessible to our study 

 in their homes are some of the flat-fishes — flounders, plaice, etc. — those queer 

 creatures that have departed so monstrously from the main piscine type. 

 Their wonderful protective coloration has long been a matter of common 

 remark; but here as elsewhere the subtle basic principle. has been overlooked. 

 Flounders and their kindred, using one broad side as a back and the other 

 as a -'bottom,' are indeed very nearly 'flat,' and their exposed upper side 

 arches but little above the surface of the sand- or pebble-bed on which they 

 rest. But a close examination shows that this 'back's' very slight convex- 

 ity is exactly compensated by a delicate obliterative shading, accelerated to 

 cope with the sharp rotundity of the back's edges, and, downward, culminating 



164 



