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 in. 



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 larvae 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 larvae 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 fun -grown mature form. 



The color variations of the adult are discussed in Chapter vin. 



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. 36, 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 

 *br food can hardly fail to he great destroyers of crustacean larvae. (See note on nienhaden, p. 122.) 



