NATURAL HISTORY OF AMERICAN LOBSTER. 345 



The seventh-stage lobsters keep as steadily to the bottom as the adults, and in 

 crawling about make use chiefly of the last three or four pairs of thoracic legs. The 

 large claws and smaller chelate legs are often extended forward in front of the head. 



In the case of a lobster which was observed to molt from the sixth to the seventh 

 stage the body was translucent, the general color being reddish brown, with a slight 

 tinge of green on the carapace. The large claws were of a bright terra-cotta color. 

 There was a whitish crescentic spot at the cervical groove on the back, and the char- 

 acteristic tendon marks on each side of the carapace were as prominent as in the sixth 

 stage. The pleura of the first abdominal somite were also snow white, and the uropods 

 were tipped with cream color. 



At the seventh stage pigment has been deposited below the enamel layer of the 

 cuticle in an amount which, though at first very slight, increases with every molt and 

 thus makes the color pattern more and more complex. 



According to Hadley (124.) the color of the seventh stage is usually and charac- 

 teristically pure slate, becoming darker during the progress of the period, showing 

 further the modifications of blue slate, green slate, and cream slate. The white spot- 

 tings, as I have frequently observed, show a tendency to become creamy or buff in 

 color in contrast to their porcelain-like whiteness in the fifth and especially in the sixth 

 stage. 



I have recorded numerous observations to show that the same animal may undergo 

 no inconsiderable changes of color during the stage period. The color at this time is 

 due to the pigments of the changing cuticle and to the changing pigments of the soft 

 skin beneath it. With the advance of the stage period a new cuticle or shell is grad- 

 ually formed beneath the old, which is later shed, with the tendency to become darker 

 or more opaque. The color is also affected in some degree by any stimulus or change 

 of the physiological state which affects the more responsive chromatophores of the soft 

 skin. 



It is therefore a difficult matter to standardize these ever-changing color effects, 

 and not possible unless the animals are compared in the same stage period, immediately 

 after molting, and under similar physical conditions. It is certain that the activity of 

 the chromatophores is not dependent upon the direction or intensity of the rays of 

 light alone, but rather more, as recent experiments seem to show, upon the physiological 

 states, which follow upon complex and little understood changes. 



Further, the act of molting by the stimulus sent into the chromatophores will 

 sometimes bleach a brilliant animal into a pale shadow of its former self, as I have 

 witnessed in the adult shrirnp Alpheus, as well as in the adolescent lobster. Accordingly 

 I consider it highly probable, if not certain, that the blue-slate or slate color is often 

 due to the advancement of the stage period and to the peculiar opacity which always 

 follows upon the development of a new cuticle beneath the old. It should also be 

 observed that the cast shell, from at least the fourth stage to the present, which veils 

 the brighter colors of the new cuticle, is blue, suffused at this time with green and 

 brown in its pigment layer. 



