16 PROCEEDINGS OP THE AMERICAN ACADEMY 



hue had so well simulated sand, a few moments before. On removing 

 him to a gravelly bottom, the spots of the side quickly became promi- 

 nent (PI. VI IT. fig. 3). During all this time, the pigments of the 

 blind side showed no trace of any sensitiveness ; while, if these ex- 

 periments are made when the eyes are still on both sides, the pigments 

 of the two sides change at the same time in a corresponding manner. 



It is well known that Squids and Cuttle Fish, provided as they are 

 witii exceedingly sensitive chromatic cells, are also able to imitate, for 

 tlieir protection and disguise, the coloring of the ground upon which 

 they happen to live. But, in Cephalopods, the change of color of these 

 chromatophores is more intimately connected with the nervous sys- 

 tem, and appears far more sensitive and less subject to control than 

 among fishes. In Cephalopods, the mere act of moving the mantle, of 

 breathing, or of forcing the water through the siphon, seems sufficient 

 to produce a change of tint ; and a sudden disturbance is as likely to 

 bring about a detrimental as a beneficial change of color."* 



Among Fishes, Reptiles, and other Vertebrates, as well as among Ce- 

 phalopods, and the mass of MoUusks, Crustacea, Annellids, Echinoderms, 

 &c., in which we find dermal pigment cells, we can readily imagine how 

 the effect of environments might, by reflex action, bring about a 

 resemblance to surrounding coloring, as has been described by Pouchet 

 and by Bert, thus producing general effects in the pigment cells, 

 which would assimilate within certain limits with the surrounding 

 tone. In all these cases, the explanation based upon mimicry as bene- 

 ficial presents little difficulty ; and we might suppose that by the laws 

 of heredity those colors alone which had been stimulated by continued 

 action through many generations would be transmitted. Thus Flounders, 

 for instance, living on sandy bottom, in which the grayish tint imitating 

 sand had been most constantly produced by the action of the proper pig- 



* See tlie papers on the chromatophores of Cephalopods, by Hubrecht, 

 Niederland. Archiv f. Zool., II. No. 3, p. 8, Mai, 1875, in which he makes a most 

 interesting comparison of the phenomena of chromatophores and protoplasmic 

 action. Also an important paper by Dr. Hagen, in the American Naturalist, 

 vol. vi., July, 1872, on mimicry in the color of insects. The general results of 

 Dr. Hagen's study of the phenomena of color in insects agree, in the main, with 

 the results obtained by Pouchet from the study of Fishes, Crustacea, and Mol- 

 lusks ; both Pouchet and Hagen recognizing the presence of colors due to 

 action of light, and the presence of colors due to pigments, the hypodermal and 

 dermal layers. Judging from the interesting discussions brought out by the 

 papers of Weismann, of Wallace, and others, on the causes of color in the animal 

 kingdom, we are, however, only on the threshold of a most interesting and 

 novel field of inquiry. 



