78 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



The color of any lobster is due to three primary pigments, all of 

 ivhich are probably lipochromes: 



1. A red pigment found in the stellate color cells or chromato- 

 phores which are very abundant of the lobster. 



2. A yellow pigment located in the yellow pigment cells, or chro- 

 matophores, which are less numerous than the red color cells. 



3. A diffuse blue pigment found throughout the body in the blood, 

 in which this pigment is soluble. 



These pigment cells are found in the epidermis or just below it in 

 the pigment producing epithelium. A distinction must be made be- 

 tween the color of the epidermis, which, in the early stages shows 

 through the thin chitinous exoskeleton, and the color of older lob- 

 sters which depends upon the amount and nature of the pigment 

 absorbed by the thick, calcerous, and opaque exoskeleton. 



Often the color of the lobsters in the early stages is modified greatly 

 by the color of the internal organs, such as stomach, intestines, liver, 

 glands, etc., which may show through the thin, transparent, and 

 chitinous wall of the exoskeleton before it has taken up from the 

 water a large amount of lime salts. 



The chromatophores themselves are granular, cytoplasmic bodies 

 of irregular stellate shape, having centers from which branch thick 

 trunks, dividing later into finer ramifications; through these the 

 pigment ebbs and flows. These cells are found in fairly regular 

 groups over the body and appendages, the groupings remaining fairly 

 constant through the first three larval stages (cf. p. 59). 



The function of the pigments of the lobster or of the crustacea in 

 general is not known. By various investigators they are held to be 

 reserve products, or functionless products of metabolism, or again, to 

 have a decided protective function ("chromatic function" of Pou- 

 chet). Protective function on the part of the chromatophores is, 

 however, difficult to demonstrate, for the changes in the color of the 



