342 BULLETIN OF THE BUREAU OF FISHERIES. 



Up to the adult state, when the shell is finely stippled with them, while the setae them- 

 selves have for the most part disappeared. 



Microscopical examination reveals a multitude of minute, closely crowded chromato- 

 phores in the skin, containing pigments of various tints, chiefly red and yellow. The 

 color pattern is due mainly to the distribution of these cells; the quality and degree 

 of color which in the same individual is subject to more or less constant variation, 

 especially before and after the molt, is determined by the expansion of the variously 

 colored chromatophores, the contents of the alimentary tract at the moment, and the 

 variable tints of the underlying gastric glands. The bluish tint and sUghtly diminished 

 translucency of the shell, when preparing to molt, has a considerable influence on the 

 color of the animal as a whole. 



The general cast of color may be either (i) yellow and red, (2) red, (3) green, or 

 (4) green and reddish-brown. In the first instance the carapace is light yellow, trans- 

 lucent, and sprinkled with red chromatophores. The abdomen and large chelae are 

 reddish-brown, and there is a quadrilateral yellowish-green area on the terga of the 

 fourth and fifth abdominal segments. In the red individuals the animal is bright red, 

 especially on the abdomen and large chelae. The carapace is yellowish, spotted with 

 red, and the abdomen is marked in the way just described. In the green variation the 

 whole animal is bright green. Bright-green areas are noticeable on the abdominal 

 terga as before, and upon the hinder portion of the carapace. There is also some brown 

 pigment on the large chelae and tail fan. In the fourth variety the abdomen and chelae 

 are rich reddish-brown, with light peacock-green on the terga of the abdominal rings, 

 as is commonly seen, and on the carapace next to the abdomen. The rest of the cara- 

 pace is greenish-brown. The characteristic tendon marks on the carapace in this and 

 in all subsequent stages define the areas of attachment of certain tendons or muscles to 

 the shell. They become most conspicuous after the fifth or sixth molt. Average length 

 at fourth stage. Woods Hole, Mass., 12.6 mm.; extremes, 11-14 mm. (64 measure- 

 ments); stage period, 10-19 days; Wickford, R. I. (Hadley for 1904), average length, 

 13.5 mm.; stage period 12 days. 



THE FIFTH STAGE. 



The lobsterling which has not made its descent to the bottom at the close of the 

 fourth stage continues to swim at the surface until the end of its fifth period, but 

 whether pelagic or an inhabitant of the bottom its behavior closely tallies with that 

 manifested in the preceding stage under similar conditions. Hadley has shown, how- 

 ever, that fifth-stage lobsters exhibit a stronger repugnance to light and a greater 

 tendency to seek sanded areas and to burrow. 



The structural changes which the lobster undergoes in passing from the fourth to 

 the fifth and again from this to the sixth stage are often so sUght as to be unrecogniz- 

 able by anyone who has not followed each stage under the microscope molt by molt. 



The salts of lime and the pigment which begin to appear in the shell at the fourth 

 stage increase, and the carapace is in most cases fairly opaque, excepting immediately 



