58 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



from which branch thick trunks, dividing later into finer ramifica- 

 tions of a more or less tubular appearance.* In such cells the red 

 or the yellow pigment lies, sometimes expanding far out into the 

 small branches, again contracting into the center, where it remains 

 evident only as a small dot of color. In cases of the greatest disten- 

 tion of these pigment cells, if they be thick in a green area, a homo- 

 geneous red coloration is produced. If in fewer numbers, each 

 individual chromatophore with all its branches is plainly visible. 

 In the early larval stages of the lobster it seems that the blue, soluble 

 pigment is to be found at nearly all times, and when the red coloration 

 is predominant it is merely because the blue color has been veiled, so 

 to speak, by the great expansion of the red chromatophores. which 

 both numerically and in comparative size are superior to the yellow. 

 As stated, the blue pigmentation is diffuse. The chromatophores, 

 however, are scattered irregularly, but often in regular groupings 

 over the body and appendages, lying for the most part in the skin or 

 cuticle or just below it. The distinction must be made, however, 

 between the pigmentation of the chitinous exoskeleton and the 

 pigmentation of the sub-adjacent epidermis in which the chroma- 

 tophores reside and from which the pigment appears to be given off 

 to the outer shell. f In the adult lobster the chromatophore-con- 

 taining epidermis is ciuite concealed by the thick, calcerous exo- 

 skeleton which has usually, at this stage, absorbed a large amount 

 of lime-salts. In the earlier stages, however, whose exoskeleton is 

 composed of thin, transparent, chitinous substance, the colorings of 

 the epidermis readily show through and continue to do so until, as 

 the stages advance and more lime-salts are added to the shell, it 

 soon becomes translucent and later opacjue. 



* Keeble and Gamble: The Color Physiology of Higher Crustacea. 



t It is readily observable by removing a bit of the shell of an adult lobster that sub-adjacent 

 to each prominent olive-green si)ot lies a dense group of reil jiigment cells. 



