60 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



may be produced, however, by the general color of the liver, alimen- 

 tary tract, glands, etc., which in the comparatively transparent 

 early stage lobsters may show through the delicate skin and produce 

 colorations, the character of which depends largely upon the food 

 of the young larvae. 



III. Function and Behavior of the Pigments in Larval 



Stages. 



The question of the possible function of these pigments in the 

 lobster, as well as in other forms of Crustacea, has yet to find a solu- 

 tion; likewise the question to what the contraction and expansion 

 of chromatophores is due. Pouchet, in his work, "Changements de 

 Coloration sous I'influence des Nerfs," gives the result of his experi- 

 mentation upon such forms as the shrimp (Palsemon), with back- 

 grounds of black and white. He finds that a black background, 

 in sunlight, causes expansion, and that a white background, under 

 the same conditions, causes contraction, of the chromatophores. He 

 concludes that the background regulates the action of the chro- 

 matophores through the medium of the nervous system, and believes 

 that this phenomenon is a case of protective or adaptive coloration. 

 Other investigators maintain that the chromatophore pigments are 

 merely a functionless product of metabolism. If we consider that a 

 similarity in the color of the individual and that of the environment 

 is a phase of protective coloration, surely experiments upon Homarus 

 hardly uphold the theory of a protective function in the color cells; 

 for in strong light the pigments are the brightest, and in the dark the 

 young lobsters are most pale. It does seem, however, that there 

 may be both protective and adaptive significance in the later 

 stages of the lobster which do not show the discontinuous variation 

 which is characteristic of the larval stages.* 



* Even in the adult lobster, however, whose dark, mottled olive brown and olive green adapt 

 him for a life at the bottom of the sea among the rocks and red and green algoe, the phenomenon 

 is probably the fortunate result of chemical influences; for, when placed in shallow water and 

 exposed to the sunlight for some time, he readily becomes Ught colored again owing to the 

 cha ge which takes place in the pigments of the calcerous exoskeleton. In this case the light- 



