ADJUSTMENT OF FLATFISHES 411 



concentration of their pigment granules as a result of mechanical 

 stimuli, the electric current, etc. From the mechanism of color 

 change, we should naturally expect that the chromatophores in 

 their resting condition would be darker than when subjected to 

 stimulus, and this appears to be the rule. 



Such, in brief, are the main facts which have been recorded 

 regarding the physiology of color change among fishes. It is my 

 purpose in the present paper to give the results of some experi- 

 ments which were conducted by me at Naples during the earlier 

 months of the year 1910, and which were continued at Woods 

 Hole during the succeeding summer.*^ In these studies, I have 

 been chiefly concerned with the relations between the stimulus and 

 the response. Very little attention has been given by me to the 

 physiological mechanism of this response, though experiments 

 with blinded fishes have, it is true, been performed. 



While viewing specimens of one of the common European tur- 

 bots, Rhombus maximus (Linn.), in the aquarium of the Naples 

 station, I was impressed by the detailed resemblance which ob- 

 tained between the markings of the skin and the appearance of the 

 gravel on which the fish rested. Now although the pattern of the 

 animal was such as to harmonize very strikingly with this gravel, 

 it would not have harmonized particularly well with fine sand, even 

 if similarly colored, nor would it have been well suited to a bottom 

 of large stones. The query at once suggested itself: Is it a mere 

 coincidence, this detailed agreement of the fish with its present 

 background, or does the fish have the power of controlling the 

 color pattern as well as the general color tone of the body? 



Curiously enough, I have found scarcely any references in the 

 literature to adaptive change in the color pattern of fishes,' 



^ A report upon some of these results, illustrated by lantern slides, was presented 

 before the research seminarof the Woods Hole laboratories last summer, and simi- 

 lar reports have been read before the American Fisheries Society, New York, 

 Septe ber, 1910 (published in the 'Transactions'), and before the American 

 Society of Zoologists, at Ithaca, December, 1910. A brief popular statement, with 

 five illustrations was published in the Zoological Society Bulletin (N. Y. Zool. 

 Soc), November, 1910. 



^ The only direct reference which I have found to differences of color pattern 

 displayed by the same fish on bottoms of different texture, is contained in Cun- 



