GENERAL SURVEY OF CHANGES IN SHADE, COLOR, AND PATTERN IN 



FISHES. 



During the summers of 191 3 and 1914 a considerable number of different fishes were 

 kept in aquaria about the laboratory at Beaufort, for various purposes, by different 

 investigators. Superficial observations were made from time to time on all of these 

 fishes. No detailed record was kept of these observations, nor were the species recorded, 

 although it may safely be said that there were at least 30. Changes in shade occurred 

 in practically all of the species observed, changes in color in a relatively large number, 

 and changes in pattern in relatively few. In some these changes were slight and insig- 

 nificant, in others very striking. Some of the changes observed occurred very suddenly 

 and were transient ; others proceeded gradually and slowly, requiring hours or even days 

 for complete adjustment. In some species most of the changes occurred without any 

 apparent reference to the environment, the stimulus evidently being internal, and in 

 these there was little evidence of adaptation. In others, nearly all of the changes were 

 clearly due to alterations in the shade, configuration, or color of the background. These 

 animals, in some instances, came to resemble their surroundings to a most remarkable 

 degree. 



In a number of the species referred to above the changes in shade, color, and 

 pattern were somewhat more thoroughly studied by putting them successively into 

 different boxes painted on the inside as follows: Black, white, white with black spots, 

 yellow, red, green, and blue. The results of these observations are briefly summarized 

 in table i. 



In judging the effect of a given background, the fishes were frequently put upon a 

 different background " and compared with specimens which had been on this long enough 

 to become fully adjusted. In most cases the changes in the skin were so marked that 

 there was not the slightest doubt concerning them. All of those concerning which there 

 was any doubt are indicated in the table by means of a question mark. 



By referring to this table it will be seen that all of the species mentioned assumed 

 a light shade on a light bottom and a dark shade on a dark bottom, and that a number 

 changed in color so as to harmonize in this respect with the bottom, but that the skin 

 assumed a pattern similar to that of the bottom in only a few species. These changes 

 were of such a nature that I was fully convinced that whatever the significance may be, 

 they are related to the background in such a way as to make the individuals incon- 



" This precaution is very important, especially in judeing the effect of the background on the color, particularly in trans- 

 lucent forms, such as Menidta. Enough light passes through these creatures to make them resemble somewhat the backgroimd 

 in color, no matter what it may be. It was foimd, however, in this case that when those which bad been in a box of a given 

 color were put into one of a different color, they still showed a predominance of the color of the box from which they had been 

 taken, in spile of the interference of the color reflected from the new background. For example, an individual taken from the 

 green box and put into the yellow bo.x appeared very distinctly green, especially above the eyes and along the sides, while in 

 the individual which had been in the yellow box continuously these same parts appeared yellow and not a trace of green could 

 be seen. In the observations, the results of which are recorded in table i, similar tests were appUed in practically all cases. 



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