SUMMARY. 



1. Adaptive changes in shade occur in the skin of practically all of the different 

 fishes found in the region of Beaufort, N. C. ; adaptive changes in color occur in many; 

 but adaptive changes in pattern in only a few. 



2. The flounders Paralichthys and A-ncylopsetfa simulate the background over a 

 wider range and more closely than any other forms studied. In nature they resemble 

 the bottom so much that it is difficult to see them, especially when they are partly 

 buried, as they usually are. They are the only forms found in which the skin changes 

 so as to resemble the bottom in pattern as well as in shade and color. 



3. Simulation of the background in Paralichthys is more extensive and more nearly 

 perfect than in Ancylopsetta. The range of changes in the skin in members of this 

 genus is most remarkable. On a white background they become almost pure white, on 

 a black background nearly black, and on gray backgrounds of various shades they 

 become gray of very nearly the same shade. 



4. On blue, green, yellow, orange, pink, or brown of various hues they assume a 

 color remarkably similar to that of the background. Reds of various tints and shades, 

 however, are not very accurately simulated ; but the color produced in the skin by each 

 tint or shade of red is different from that produced by any other color and very different 

 from that produced by gray regardless of the intensity. 



5. On bottoms containing black and white squares or circles, the skin breaks up 

 into similar areas both in size and shade, but in no case is there any indication of an 

 actual reproduction of the form of the areas, as maintained by Pitkin and Loeb. Large 

 figures in the background produce a coarse pattern in the skin, and small figures a fine 

 pattern, but Squares of a given size produce essentially the same pattern as circles or 

 stripes, or within certain limits any other figures of the same size. 



6. The size of the light and dark areas in the background and the relative amount 

 of surface covered by them have a profound effect on the pattern produced in the skin, 

 but the form and arrangement have little or no effect. 



7. The large features in the pattern are essentially the same in different individuals 

 'of the same species, but the details differ so much that any individual could readily be 



recognized by a careful study of less than a square millimeter of any portion of the 

 pigmented surface. 



8. The time required for adaptation to colors is, in general, much longer than that 

 required for adaptation in shade or pattern. On the reds, greens, and blues adaptive 

 changes still appear to continue after a sojourn on them of between two and three 

 months. On yellows and browns adaptation occurs in much shorter time. This may 

 be due to the predominance of these colors in the normal environment of the flounders. 



9. The time required for adaptive changes in shade may be greatly reduced by 

 repetition. In one individual, in the course of a week, it was reduced from five days 

 to less than two minutes by repeated changes from black to white and vice versa. 



22s 



