376 



SCIENCE. 



[X. S. Vol. XXI. Xo. 5.32. 



regeneration, like the phenomena observed 

 by Przibram in Alphcus. 



Torsion in the Crustacean Lhnh: Francis 

 H. Herbick, Western Reserve University. 

 In crayfishes and lobsters the dactyles of 

 the great claws face, and, therefore, open 

 inward and in a nearly horizontal plane, 

 while the smaller chelae open upward and 

 outward in a plane which is nearly vertical. 

 In the lobster at birth, however, the chelae, 

 legs, great and small, all have the same form 

 and position, that is, the laterally com- 

 pressed claws all open vertically with an 

 inclination outward. It, therefore, follows 

 that the position of the great 'forceps' has 

 been reversed by a rotation through 90°, in 

 consequence of which their inner or an- 

 terior faces have become their under sides. 

 With crayfishes, in which the metamor- 

 phosis is far more abbreviated, the adult 

 form is already acquired at birth, so we 

 may infer that this change has occurred in 

 the embryo, for otherwise we should have 

 to assume that the ancestors of the cray- 

 fish possessed another type of claw, which 

 is not the case. 



In the crayfish about one quarter of the 

 weight of the animal is i"epresented by the 

 great ehelipeds, while the proportional 

 weight in the lobster is one half. The 

 acquisition of size and strength in these 

 limbs, and in Homarus the remarkable dif- 

 ferentiation into toothed and crushing 

 forceps of right or left sides, have been at- 

 tended by a permanent torsion, which has 

 chiefly affected the carpodite or fifth point. 

 As can be clearly shown, hoAvever, this 

 twisting is entirely independent of the 

 form or weight of the claw. Meanwhile 

 the eight slender legs have remained sta- 

 tionary, retaining their larval form and 

 position. 



The rotation of the chela in the lobster is 

 completed at the fourth molt, which marks 

 the most striking leap in the history of 



development. The change is unquestion- 

 ably of very ancient origin, and is probably 

 older than autotomy, which precedes regen- 

 eration in certain limbs, since fusion of the 

 second and third joints does not occur until 

 after the fifth stage. It was already per- 

 fected during the Liassic period in the 

 Erymoid Crustacea, which are regarded as 

 the direct ancestors of modern crayfishes 

 and lobsters. 



Torsion in the crustacean limb can not 

 be explained on Lamarekian principles, 

 since, owing to the peculiar structure of the 

 segmented limb, with its fixed hinge joints, 

 the muscles of a given segment can deliver 

 only straight pulls on the next distal seg- 

 ment, which could not produce a torsion of 

 the joint in which the muscles are lodged. 



The theory of natural selection fares no 

 better, for it is impossible to suppose that 

 the toreion could have arisen gradually, 

 through successive fractions of a degree, 

 each position being more favorable than 

 the last, and especially since in hundreds 

 of crabs and prawns the claws open upward 

 and outward. It seems more probable that 

 the condition was acquired suddenly as a 

 discontinuous variation, which has become 

 adaptive in a minor degree. 



The Growth of the Tail of the Japanese 

 Long-tailed Fowl: C. B. Davenport, Sta- 

 tion for Experimental Evolution, Cold 

 Spring Harbor, N. Y. 

 A preliminary report on the anatomy of 

 the tail of the fowl and the morphologic 

 basis of the long tail. A comparison of 

 the tails of two brothers, one of which has 

 had the tail feathers regularly stroked, the 

 other not. 



A Problem in Degeneration: Charles B. 

 AViLSON, State Normal School, Westfield, 

 Mass. 



The group of parasitic eopepods affords 

 one of the very best opportunities for 



