TORSION OF THE CRUSTACEAN LIMB. 131 



size and strength in these limbs, and in Homams the remarkable 

 differentiation into toothed and crushing forceps of either right 



Fig.l 



4 



FlGS. I and 2. Left first and third chelipeds of Homants americaniis in natural 

 position, seen from above. Pins 1-5 are inserted close to the hinge joints of the suc- 

 cessive segments in each limb, to illustrate the degree of torsion which the great 

 chelipeds have undergone. Compare the position of the hinge-joints I and 2, Fig. 

 I, with that of the corresponding joints in Fig. 2. Cf, Carpodite ; D, dactyle ; p, 

 propodite ; 1-6, pins inserted in hinge-joints. 



or left sides, has been accompanied by a permanent torsion, 

 which has chiefly affected the carpodite, or fifth joint (as counted 



