502 MEMOIRS OF THE CARNEGIE MUSEUM 



keel of the rostrum, and in that of tlie spines and the cavpopodite and raeropodite 

 of the cheHpeds, and we have also seen that there is sometimes a notch on the 

 anterior margin of the male organ. All these characters mark a certain inclination 

 toward C. obscurus which will be discussed below. 



The six hundred and eighty-seven specimens of C. obsc2trus at hand are, as has 

 been seen above, very uniform in their cliaracters. A tendency has been observed 

 toward an increase of the spines of the meropodite of the cheliped in a direction 

 from the northeast toward the southwest within the range of this species. Here we 

 have apparently the first step toward the formation of a variety : a variation 

 becomes more frequent in the southwestern part of the range, possibly in conse- 

 quence of hereditary transmission, and begins to " breed true." But it is only the 

 beginning of it, the varying form not being found to the exclusion of the original, 

 and thus it remains " variation " only. 



Other variations (mentioned p. 375 and 37G) are very likely due to injuries re- 

 ceived during life*^ and again others are of the character of freaks, namely the two 

 cases of apparent hermaphroditism. One of these is rather interesting (PI. XXXIX, 

 Fig. 7*^ and 7''). Here the male sexual organs do not at all correspond to the typical 

 form of this species, but approach in shape to that known in the ////losH.s-section. It 

 seems to me that we have to deal here with a case of atavism. The /imostts-section has 

 been regarded as the most primitive type of the subgenus Faxonius, on account of the 

 very slightly separated tips of the copulatory organs. The propinqims-sQoWou is next 

 to it, but here the tips are separated for a greater distance. It is quite probable 

 that the latter section descended directly from the* former, and it seems that in the 

 instance discussed the sexual organs have reverted to the original Umosus-iypQ, and 

 thus the assumption that the 'propinquiis-seciion is a descendant of the limusus- 

 section gains additional strength. 



In the seven hundred and twenty-five specimens of C. bartoni we again have to 

 emphasize the great uniformity of the characters. The variations discussed are 

 rather insignificant, and consist chiefly in the shape of the rostrum and the size. 

 A single individual has been observed in which one lateral spine of the carapace 

 was present, apparently an atavistic feature. Othei' variations are of the hermaph- 

 roditic type. 



No remarkable variations have been found in C. carolinus, and a few insignifi- 



*• Variations due to injuries are most frequently observed in the case of regeneration of the chelipeds. I did 

 not mention them in the systematic part, since they are very common. If the claws are lost they are replaced by new 

 claws, which differ from the old ones not only in size, but also in shape. The fingers are proportionally longer, and the 

 palm proportionally shorter than in normal claws. This difference in shape remains even if the claws, after repeated 

 moults, again attain a good size. Regenerated claws may always be recognized by the short palm and long lingers. 



