. Natural history of the American Decapoda (Crustacea); Lobster fisheries. 258 BULLETIN OF THE BUREAU OF FISHERIES. their under sides. This rotation is completely effected at the fourth stage (pi. xxxi) and with the molt which registers so many other marked changes in the structure and habits of this animal. It is responsible for the torsion or twist to be clearly seen in the carpus of the limb. In conformity with this change in position, the claw has undergone a change in coloring, for the deep green chromogen pigments which cover the present upper surfaces are completely lacking f
. Natural history of the American Decapoda (Crustacea); Lobster fisheries. 258 BULLETIN OF THE BUREAU OF FISHERIES. their under sides. This rotation is completely effected at the fourth stage (pi. xxxi) and with the molt which registers so many other marked changes in the structure and habits of this animal. It is responsible for the torsion or twist to be clearly seen in the carpus of the limb. In conformity with this change in position, the claw has undergone a change in coloring, for the deep green chromogen pigments which cover the present upper surfaces are completely lacking from their pale red under sides. It would appear in the highest degree improbable that this condition in the big claws could have been produced through the in- heritance of slight variations leading to a g / I greater and greater degree of torsion, and finally extending through so great an arc, '^ although it is conceivable that such a p /_ AV^^-" 7 variation may have been correlated with others which were of so favorable a char- acter as to be of selective value and to have been "dragged" along with them. Again, it is even more difficult to re- 6 gard this torsion of the crustacean limb as ] \^ \- Cp the resultant effect of use through inher- itance. The carpal podomere has but 7'"' / / '^''^ » ^^ 5 one flexor and one extensor muscle, both â " ^^^vl_^rTy of which react on the claw at points out- - K"^ ^J- -^1 >v -'' ^^^^ °^ ^^^ joint itself; at the same time -Cp ^v) â â¢^'^v»*--2 ^^^ muscles, of course, pull on the shell of this part at their points of origin, but no conceivable position or strain of these Sâ-z^^^ \ ^ -J M,- 4 fibers can convert the pull into a twist. ⢠2 If the increasing weight of the claws in the growing animal had any effect upon - 5 their ultimate position it should tend to ^ ,!,,,.,, , turn them outward. In other words, their Fig. 6 and 7.âGreat first and small left third claw feet of adult lobste
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