July 19, 1907] 



SCIENCE 



83 



following the instructions of the president, 

 not to grant any cession of land from the ter- 

 ritory of the United States. 



The only comfort which can be derived 

 from this crying over spilt milk is that relief 

 which comes with a gush of tears, and from 

 the satisfaction of remembering " what might 

 have been." N. H. Winchell 



Minnesota Histoeicai Society, 

 May, 1907 



REGENERATION AND THE QUESTION OF " SYM- 

 METRY IN THE BIG CLAWS OF THE 

 LOBSTER " 



In view of several recent articles* on the 

 phenomena of symmetrical chelae in the lobster 

 it seems desirable to offer a few further con- 

 siderations on the subject of the origin of 

 such structures. 



Let us briefly present the nature of the 

 problem. It is a matter of common observa- 

 tion that in the adult lobster the " great " 

 claws are almost invariably asymmetrical with 

 reference to each other; the claw on one side 

 of the body being a " nipper " and the other a 

 " crusher." In a few cases, however, a varia- 

 tion from this normal asymmetry has been 

 discovered, in which the claws instead of dif- 

 fering from each other are very much alike 

 and symmetrical in form. These variations 

 fall into two categories : First, those in which 

 both claws are of the nipper type, and second, 

 those in which the similar claws are both 

 crushers. Two theories for the origin of these 

 relations of symmetry have been presented — 

 first, that they are predetermined in the egg, 

 and second that they may arise through re- 

 generative processes and consequently, are not 

 of necessity wholly determined by congenital 

 factors. Let us consider first the variations 

 from normal asymmetry. 

 I. Explanations for Abnormally Symmetrical 



Claws. 



(a) Similar Nipper Claws. — Until very re- 

 cently in all the authentic cases of similar 

 chelae, the claws belonged to the first category 

 of the nipper type. Out of over 2,400 



'See especially: (1) Herrick, F. H., 1007, 

 " Symmetry in the Big Claws of the Lobster," 

 Science, Vol. XXV., p. 275. (2) Caiman, W. T., 

 1006, in the " Proceedings of the Zoological So- 

 ciety of London," p. 633. 



lobsters" found only three had similar claws. 

 In an examination of some 600 specimens as 

 they came in from the traps at the Experi- 

 ment Station of the Ehode Island Commis- 

 sion of Inland Tisheries the writer' found 

 only one lobster with both claws alike. The 

 similar claws of these four cases were all 

 nippers. Theoretically, it may appear quite 

 plausible that a symmetry of this character 

 might be congenital in origin. For in the 

 early development of the lobster both chelaj 

 are alike and similar to the nipper type. At 

 about the sixth stage* normally one of the 

 claws begins to differentiate into a crusher. 

 We might thus have an adult lobster with two 

 nipping claws because they had failed to dif- 

 ferentiate in the usual asymmetrical manner. 

 On the other hand, the writer has elsewhere' 

 furnished evidence that this type of sym- 

 metry may also be brought about as the result 

 of a process of regeneration. 



(h) Similar Crusher Claws. — With regard 

 to this second category, however, tSe con- 

 genital theory does not appear to apply so 

 readily. For in this case the development 

 must be conceived as starting in the normal 

 way, and then instead of differentiating 

 asymmetrically both chelae have passed beyond 

 the normal stages and developed into two 

 crushing claws of the phylogenetically later 

 (according to Stahr" and Przibram') type. 



'Herrick, F. H., 1895, "The American Lobster," 

 Bull. U. S. Fish Commission. 



'Emmel, V. E., 1907, "Regenerated and Ab- 

 normal Appendages in the Lobster," thirty-sixth 

 annual report of the Rhode Island Commission 

 of Inland Fisheries, special paper. No. 31. 



• Hadley, P. B., 1906, " Changes in Form and 

 Color in Successive Stages of the American Lob- 

 ster," thirty-fifth annual report of the Rhode 

 Island Commission of Inland Fisheries, Special 

 paper No. 19. 



" Emmel, V. E., 1906, " Torsion and other Transi- 

 tional Phenomena in the Regeneration of the 

 Cheliped of the Lobster," Journ. of Exp. Zoology, 

 Vol. III., No. 4. 



"Stahr, H., 1808, " Neue Beitrage zur Mor- 

 jjliologie der Hummerschere Jena," Zeitsclir. f. 

 Waturw., Bd. 32. 



'Przibram, H., 1901, " Experimentelle studien 

 iiber Regeneration, I.," Archiv. f. Entiv.-Mech., 

 Bd. XL 



