2O8 EDMUND 15. WILSON. 



Figs. 2, />, 2, E. The former shows the transformed small chela 

 of the male, the latter that of the female. The former is in every 

 respect - - general proportions, depth of transverse groove, shape 

 and proportion of the claws - - more highly modified in the direc- 

 tion of the adult hammer-chela, though the period since the 

 operation was eleven days, while in case of the female it was 

 sixteen. 



These facts seem to leave no doubt that the female small chela 

 represents a relatively undeveloped or larval type, that of the 

 male a further development of the same type, accompanied by 

 the appearance of certain specialized secondary sexual features 

 (setose ridge), while the large chela is the extreme of the same 

 line of development. The male small chela is more rapidly 

 transformed into one of the large type, common to both sexes, 

 because it has already advanced further on this line than that of 

 the female. 



COMMENT. 



In the above facts we probably find a basis for an interpreta- 

 tion of the reversal of asymmetry during regeneration. The 

 great size of the large chela in AlpJiens, and its importance as a 

 weapon of offense and defense which Brooks and Herrick pointed 

 out, suggest at once the teleological interpretation that the re- 

 versal is a device to secure the least possible delay in the restor- 

 ation of an important organ by utilizing a structure already 

 present as the foundation of the large chela. That this result is 

 actually effected by the reversal is beyond question ; but we 

 need not for this reason assume that the reversal has been speci- 

 ally acquired for this purpose. Structurally the small chela of 

 the female represents a large chela in a state of arrested develop- 

 ment, with hardly noticeable modifications of the larval type. 1 

 That of the male represents a slightly more advanced develop- 

 ment along the same line, together with certain special modifica- 

 tions notably the setose ridge upon the clactylus. In both 

 sexes, accordingly, its transformation into a hammer-chela repre- 



1 The figures of Brooks and Herrick (op. cit. , Plate XX., Figs. 2, 3) of the larval 

 form of this species are not sufficiently detailed to prove this completely, but show 

 both chelae of equal size and, as far as can be judged, nearly similar in form to the 

 adult female small chela, or the regenerating small chela of both sexes. 



