THE SPERM-RECEPTACLE IN CAMBARUS. 



183 



seen in a specimen made transparent ; the broken line stands for 

 the bottom of the pocket and the parallel rulings indicate the 

 cavity of the pocket, which is about the same thing as a plane 

 passed from the mouth to the bottom, since the width of the 

 pocket is so little. It will be seen that the cavity of the pocket 

 inclines first to the right, then to the left and again somewhat to 

 the right, nearest to the observer. The bottom is thus more 

 sinuous than the mouth ; the broken line in the figure more bent 

 than the continuous line that represents the mouth. Such in- 

 clination of the sperm-pocket is the 



rule and the S-shaped curve is com- ^i::::^^^^-^ - — ■ 



mon in the higher species. In /' x^ 



another point this sperm-pocket sug- 

 gests the complex conditions in the 

 annuli of C. virilis and C. affinis, 

 and that is, the conformation of the 

 posterior part of the pocket. The 

 bottom of the pocket is not coexten- 

 sive with the mouth, so that the 

 mouth runs along the surface beyond 

 the limits of the bottom, both at the 

 anterior and the posterior ends. At 

 the posterior end the connection of 

 the mouth with the bottom is by an 

 inclined passage, sloping from the 

 surface forward. This passage is 

 slightly dilated right and left, as 

 indicated in Fig. 12. This little 

 chamber so formed is quite near the surface and farther from 

 the bottom of the pocket. It seems to be the same thing as the 

 '* recess " in which the sperm remains longer than elsewhere in 

 the annulus of C. affinis. But this chamber is easily understood 

 in this species, while in C. affinis it is obscure at first view. 



The thick shell walls of the pocket are indicated in the figure 

 by the dotted lines ; the shell that lines the pocket was removed, 

 in preparation, from the epidermis and then it was seen that the 

 epidermis that had formed this pocket was an S-shaped, deep 

 groove, out of which the S-shaped shell represented by the dotted 



Fig. 12. Ventral view of 

 sperm-pocket, as translucent 

 object, 4^. 



