July 19, 1907] 



SCIENCE 



85 



the segments of the future limbs were well out- 

 lined, attention was drawn to the very similar 

 appearance of the two regenerating structures. 

 Usually, as the lobster approaches the culmination 

 of the moulting period, the regenerating chelse 

 become so clearly differentiated that a distinction 

 between the crusher and nipper can be readily 

 detected. In the present case, however, no char- 

 acteristic differences could be observed between 

 the right and left regenerating buds, and, more- 

 over, the general morphological appearance of each 

 suggested that both were developing into the 

 crusher type of claws. 



After the lobster had moulted, the regenerated 

 chelse assumed their normal shape and each meas- 

 ured 63 mm. in length. But the regenerative proc- 

 esses had not reproduced the original asymmet- 

 rical type of chelse. The regenerated left claw was 

 a true crusher like the former claw; but the re- 

 generated right claw had the general characters, 

 not of the nipper, but of a typical crusher. A 

 close analysis of the structural features of the 

 regenerated right claw demonstrated that, in all 

 its morphological characters, it corresponded point 

 for point with both the normal and the regener- 

 ated crusher of the left side, with respect to the 

 general form, size and proportion, in the shape 

 and arrangement of the teeth, and even in the 

 number and distribution of the tufts of tactile 

 hairs. 



Specimen B. — This specimen was an eight-inch 

 male lobster. The original chelae, ,as in the pre- 

 ceding case, were also of the normal asymmetrical 

 tj'pe, except that in this lobster the right claw 

 was the crusher and the left a nipper. Each chela 

 measured 162 mm. in length. 



On August 4, 1906, both chelae and the second 

 left leg were autotomously removed. Soon after 

 the operation another pair of limbs began to re- 

 generate. By the time the segments of the future 

 appendages were well outlined, the two regener- 

 ating chelae looked very much alike, and the fact 

 that their external characters resembled those of a 

 crusher, suggested that both limbs would develop 

 claws of a crushing type. 



By the middle of October, 1906, the lobster had 

 moulted and regenerated both chelae and the sec- 

 ond right leg. Each chela measured 111 mm. in 

 length; they were remarkably similar in Structure, 

 and each displayed the character of a typical 

 crushing claw. 



In these lobsters, therefore, we have two 

 cases in which the regenerated claws were 



symmetrical in form and of the crusher type 

 of chelse. 



With regard to tlie origin of similar 

 crusher chelse, Dr. Caiman's case has been 

 interpreted as discrediting the regeneration 

 theory for symmetrical chelse, for in his dis-. 

 cussion he says : It has been supposed that 

 this might be due to regeneration after in- 

 jury, since it is known that in Brachyura, on 

 removal of the crushing-claw, a cutting-claw 

 is regenerated. Przibram, however, failed to 

 obtain such " heteromorphie " regeneration in 

 the lobster, and the present specimen throws 

 still further doubt on the regeneration theory, 

 since it possesses a well-developed and quite 

 typical crushing-chelffi on both sides of the 

 body." 



Herrick in his earlier writing" has evi- 

 dently also favored the congenital theory, for 

 in his discussion of symmetrical claws he 

 states that " there seems to be about as much 

 variation as regards the details here men- 

 tioned in normal symmetrical claws as in the 

 abnormally symmetrical ones, and it is prob- 

 able that in either case the conditions met 

 with are to some extent congenital" (p. 244). 

 In his recent article he discusses both theories 

 without definitely favoring either, and in con- 

 clusion states that, " The explanation just 

 offered is based on the assumption that re- 

 generation, following loss, actually occurs in 

 these cases. If there has been no regenera- 

 tion, we must then fall back upon the view 

 that asymmetry in the great forceps is 

 normally produced by changes which take 

 place in the egg, so the rare condition of 

 symmetry in these appendages may be 

 casually brought about in the same way " (p. 

 277). With regard to Dr. Calmans's case of 

 two crusher claws, Herrick suggests the pos- 

 sibility of getting such a condition through a 

 process of regeneration. But it is important 

 to note that neither of these writers furnishes 

 any experimental proof for the conclusion that 

 symmetrical crushing chelse have arisen either 

 congenitally or as the result of regenera- 

 tion. The two cases just described furnish 



" Loc. cit. ( 1 ) . 

 '=Loo. cit. (2). 



