REPORT OF COMMISSIONERS OF INLAND FISHERIES. 59 



II. Groupings of the Chromatophores. 



The distriljiition of pigment, including both the diffusion of the 

 bhie and the arrangement and grouping of the color cells, appears 

 to be fairly uniform in the first three larval stages of the lobster. A 

 slight variation may often appear in the third larva, however, 

 namely, — the development of green blotches along the abdomen, 

 thus somewhat anticipating certain characteristics of the fourth 

 stage.* Generally speaking, the yellow pigment cells are not numer- 

 ous, and have no regular arrangement either as individuals or as 

 groups. Of the red chromatophores however, six fairly constant and 

 well-defined groupings may be considered. (Plates XXIII, XVII.) 



1. On the dorsal surface of the carapace in areas posterior and 

 lateral to the region of the stomach. 



2. Along the ventral and lateral border of the carapace where 

 one complete row surmounted by a few irregularly placed cells is to 

 be discerned. 



3. In well-defined groups or frequently (especially in the third 

 stage) in large individual cells, occurring in the dorsal region of the 

 first three abdominal segments, close to and on either side of the 

 mid-line. 



4. In a variable area about the mid-anterior region of the last 

 abdominal segment, where the chromatophores are often smaller and 

 more scattered. 



5. In the thoracic appendages on the segments nearest the body. 



6. Throughout all segments of the chelipeds, especially in the 

 third stage. 



The groupings, or " chromatophore centers," as termed by Keeble 

 and Gamble, t somatic, neural, visceral, and caudal, seem to have but 

 little significance for color-distribution in Homarus, where in the 

 internal organs are not highly pigmented. Several varieties of color 



* This olive green was not noticed in any of the preceding stages and was quite different from 

 the lighter yellowish green which was, in those stages, very prominent on the sides of the cara- 

 pace and abdomen. 



t Keeble and Gamble' Color Physiology of Higher Crustacea. 



