71 



will soon become almost as deep and bright as in life. In a 

 few seconds it fades again, and cannot again be brightened. 



This phenomenon leads to the consideration of another 

 peculiarity in the arrangement of the pigment cellswhich ren- 

 ders rapid changes possible in hue in certain species. In these 

 the pigments are associated with oily matter, and are arranged 

 areclas, which favor their approach toward or retreat from the 

 surface of the skin. The accompanying diagram, drawn by 

 Prof. Benecke, shows how they 

 may sometimes show as small, 

 irregular spots upon the skin, 

 and soon after become conspic- 

 uous star- shaped markings with 

 far-reaching arms. Such changes 

 may be effected by stimulation 

 of various kinds ; and even by 

 the reflex action of the nerves 

 under the influence of impres- 

 sions of color received by the 

 eye of the fish. 



Every angler knows that trout inhabiting stagnant pools 

 or dark bottoms are deep colored, while those from deep, 

 sunny waters are brighter. The same is true of many other 

 fishes. I have often seen the common flat-fish change its 

 color to that of the gravel and sand in which it was trying to 

 hide, the hue varying as rapidly as that of the landscape when 

 the sunlight is suddenly cut off by a passing cloud. 



These changes of color are directly connected with the im- 

 pressions of color received by the eye, and brought about by 

 the reflex action of the nervous system. In no other way 

 can changes such as these already referred to in flounders be 

 accounted for. I have seen the tropical squid in Bermuda 

 change color rapidly, and at will, while being pursued. This 

 was evidently through the influence of emotion or fear, since 

 it can hardly be supposed that there was definite purpose in 

 the act, which, however, seemed at first sight to be intended 

 to baffle its pursuers. 



Chromatophores variously expanded. 



