276 



SCIENCE 



[N. S. Vol. XXV. No. 633 



who found this variation of similar toothed 

 claws much more common in the European 

 lobster. The history of development proves, 

 as Stahr upon theoretical grounds maintained, 

 that the toothed claw represents the more 

 primitive, and the crushing claw the more 

 modified, type. It, therefore, seemed natural 

 to infer, as he did, that the anomalous sym- 

 metry in these weapons had been brought 

 about by loss of a crushing claw, and subse- 

 quent reversion to the primitive toothed con- 

 dition in the regenerated member which took 

 its place. This would give us a lobster with 

 symmetrical toothed claws like the variation 

 described. 



The converse of this, or the production of a 

 new crushing claw in place of a toothed ' for- 

 ceps ' could not occur upon Stahr's theory of 

 regeneration, and hence he inferred that my 

 report of a case of similar crushing claws in 

 a lobster was an error. Herr Stahr is not to 

 be blamed, for this report was based upon the 

 statement of a fisherman. Yet, however great 

 the unreliability of this class of men in biolog- 

 ical matters, I have yet to find a ' lobsterman ' 

 who could not tell a ' club ' from a ' quick ' 

 claw. It now seems that the maligned fisher- 

 man was right, and he should get his dues, 

 while Herr Stahr's theory will have to be 

 revised, for Dr. W. T. Caiman, of the British 

 Museum, has recently described' a case of 

 symmetrical crushing claws in the British 

 lobster (Homarus gammarus), and his account 

 is accompanied by an excellent photograph. 

 In all other respects this animal was a per- 

 fectly normal male. It was caught near 

 Stromness, Orkney, and its living weight was 

 four pounds ten ounces. 



In a letter regarding this unique specimen 

 Dr. Caiman says : 



The correspondence between the two chelse ag 

 regards arrangement and size of the crushing 

 tubercles is even closer than app,ears on the photo- 

 graph, where slight difi'eicn"es of color have a 

 little obscured the shape in one or two points. 

 The differences are no greater than one would 

 expect to find between the two sides of a normally 

 symmetrical animal. In other respects the 

 chelipeds are practically alike in size and shape, 



' In Proceedings of the Zoological Society of 

 London for 1906. 



except that, as seen on the figure, the dactylus 

 of the left is shorter than that of the right. The 

 basal segments of the limbs show no trace of 

 asymmetry which is often associated with re- 

 generation. 



The shrimp Alpheus carries a huge ' ham- 

 mer,' or snapping, claw, which in some species 

 is as large as the entire body of the animal, 

 and a diminutive claw of more primitive form 

 on the opposite side. Moreover, in the com- 

 mon Alpheus heterochelis of the southern 

 coast the small chela presents an interesting 

 sexual variation of which I have drawings and 

 notes made in 1893, but about which nothing 

 had been published until the appearance of 

 Wilson's interesting studies on the ' Reversal 

 of Asymmetry in Alpheus ' in 1903. The 

 small chela of the male resembles the ' ham- 

 mer ' more closely than does the correspond- 

 ing simpler and more primitive claw of the 



A remarkable example of heteromorphic re- 

 generation or reversal of asymmetry is seen 

 when the Alpheus 'shoots' its 'hammer,' or 

 for any cause loses its big claw, as was discov- 

 ered by Prizibram in 1891. The big claw 

 seems to hold the little one in cheek, for no 

 sooner is it lost than the smaller one grows 

 apace, and becomes differentiated into a ' ham- 

 mer ' or a ' snapper,' while in compensation 

 for this change a diminutive chela of the 

 primitive type replaces the great claw lost 

 from the opposite side. Wilson found that in 

 both sexes the small' claw, which was regen- 

 erated from the stump of the large one, was 

 always of the simpler female type, and, more- 

 over, that the small chela of the male was 

 more rapidly changed into the big ' pistol ' or 

 ' hammer ' claw because it was already farther 

 advanced on this line of development than 

 that of the female. When the smaller claw 

 is amputated, or when the ' forceps ' are re- 

 moved from both sides of the body at once, 

 there is no reversal, a new cutting chela or 

 hammer claw taking the place of the corre- 

 sponding member lost. Many additional facts 

 have been brought to light through the experi- 

 mental studies of Wilson, Brues and Zeleny. 



In the lobster no reversal or compensatory 

 regulation normally or usually attends the re- 



