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 shrimp 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. 
