502 MEMOIRS OF THE CARNEGIE MUSEUM 
keel of the rostrum, and in that of the spines and the carpopodite and meropodite 
of the chelipeds, 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. obscwrus which will be discussed below. 
The six hundred and eighty-seven specimens of C. obscwrus at hand are, as has 
been seen above, very uniform in their characters. 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 376) 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 (Pl. XX XIX, 
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 limosus-section. It 
seems to me that we have to deal here with a case of atavism. The /imosus-section has 
been regarded as the most primitive type of the subgenus Maxonius, on account of the 
very slightly separated tips of the copulatory organs. The propinquwus-section 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 /imosus-type, and 
thus the assumption that the propinquwus-section is a descendant of the limosus- 
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. Other variations are of the hermaph- 
roditic type. 
No remarkable variations have been found in ©. 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 alsoin 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 fingers. 
