ORGANS FOR SPERM-TRANSFER 241 
CAMBARUS AFFINIS 
While the sexual habits of all the species of Cambarus, agree 
in the main, the species affinis has been more studied, and as in 
describing the female organs concerned in sperm transfer we first 
considered this species, we will also give chief attention to the 
male organs of sperm transfer in this species. 
As elsewhere described (4, 5) conjugation is here a long series of 
activities of the male accomplishing the accurate adjustment of 
the essential transfer organs of the male to the receptacle of the 
female. The receptacle of the female is a single pouch in the shell, 
but the transfer organs of the male are three pairs of outgrowths. 
On each side of the body there is a papilla, or special termination 
of the sperm duct, and two limbs, those of the first and second 
segments of the abdomen, which we may call the stylets. 
To introduce the sperm into the receptacle the papilla must be 
adjusted both to the first and to the second stylet and both sides of 
the body play a necessary part in the process of sperm transfer. 
THE PAPILLAE 
One external instrument concerned in the process of sperm 
transfer is the modified end of the sperm duct that emerges from 
the base of the fifth leg, on each side of the animal. These organs 
are the papillae. 
Since systematic work has been done largely upon preserved 
specimens it is not so generally known that the sperm duct ends in 
life, in a soft, turgid protuberance, which may be so collapsed after 
death as to leave only the rounded hole in the firmer shell as the 
apparent ending of the sperm duct. These papillae lie concealed 
by the stylets, at rest, but on raising the stylets the papillae are 
seen as conspicuous, clear, tubes about 3 mm. long and 13 mm. 
wide, jutting out from the base of each fifth leg. 
At the time of conjugation the papillae are also concealed from 
view since the necks of the first and the second stylets form a 
nicely adjusted frame about the papillae and this frame is fitted 
in between the bases of the fifth legs. Certain in and out move- 
