184 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
shell, which soon becomes wholly responsible for the color of the animal. The dorsal 
median stripe of the carapace is much narrower than when first observed in the fourth 
stage (fig. 115), and the areas of absorption of lime salts from the lower segments 
(meros and ischium) of the large chelipeds are clearly outlined. The molting and 
growth of the adult animal are fully discussed in Chapter hi. 
COLOR VARIATIONS IN THE YOUNG LOBSTER. 
In the description of the larval stages just given I have purposely dwelt upon the 
color changes which the young animal undergoes. This is intended to supplement 
the previous observations upon the color variations of the adult. To sum up these 
detailed accounts, we find that the color of the first four larval stages is subject to 
considerable individual variation, due to the transparency of the shell and the con- 
tractility of the chromatophores which lie beneath it. In the first larva the pigment 
cells are relatively few, and respond to the slightest stimulus. With the growth of 
the animal they become very numerous, more differentiated, and so commingled that 
a very varied color pattern results. It is probable that in these stages their chief role 
is a physiological one. A transparent and almost colorless larva swimming at the 
surface of the ocean would undoubtedly be safer than a brilliantly colored one, but the 
indiscriminate destruction of these larvne is so great, both on the part of animate 1 
and inanimate foes, that such protection would count for little. That it really counts 
for nothing is shown by the fact that the fourth larva (also a pelagic animal) is almost 
invariably richly colored and is far more conspicuous at the surface than it would be if 
colorless. Again, it is not likely that larvfe know any such thing as fear, and the 
chromatophores appear to expand under any unusual stimulus. 
The color variations of the larva are the expression of physical and chemical 
changes taking place in the body, as the result, for the most part, of physiological 
conditions. Some of these changes are sudden or discontinuous, and have no adaptive 
or protective significance. 
After the fourth molt pigment begins to appear in the chitinous shell and a com- 
plicated color pattern is gradually produced which, as I have already shown, has, in all 
probability, a protective value. This happens when the young animal has given up 
its pelagic life and lives upon the sea bottom, having essentially the characters of 
the full-grown mature form. 
The color variations of the adult are discussed in Chapter ym. 
THE DEATH-FEIGNING HABIT. 
It was a matter of no little surprise to find that young lobsters in the fourth and 
fifth stages sometimes exhibit in a striking degree the remarkable phenomenon known 
as “feigning death.” It is not strictly a habit, since it does not appear in all larvae. 
Some display it upon the least provocation, the greater number but seldom or not 
at all. I have observed the same thing in a lobster over a year old, but have seen no 
trace of it in the adult. 
A young lobster to which I have already referred (No. 30, table 34) when examined 
two days after the fifth molt showed this peculiarity in a typical way. When stroked 
lightly with the finger it would immediately stiffen, and lie stretched out at the bottom 
1 Such as herring, mackerel, and menhaden, which from their peculiar habits of straining water 
for food can hardly fail to he great destroyers of crustacean larvfe. (See note on menhaden, p. 122.) 
