172 E. A. ANDREWS. 



ular function, but he recognized that it was a good aid in de- 

 scribing species of Cambarus and called it the annulus ventralis. 

 Since then it has been constantly made use of as a specific char- 

 acter. In 1895 we showed that the male of Cambarus affinis 

 deposits the sperm within a cavity in the annulus and subse- 

 quently we described the seminal receptacle in several species of 

 Carnbarus as a narrow pocket in the wall of the annular plate, 

 which arose in the young female as a shallow epidermal pit that 

 later deepened as a zigzag pocket. 



In all crayfishes except Cambarus no receptacle is known 

 and no specialization of the annular plate is known outside of 

 the females of Catnbarus and of the American lobster. Yet 

 some sort of receptacle may yet be found in other crayfishes. 

 Thus the crayfishes of eastern Asia have the annular plate hol- 

 lowed out posteriorly, the male stylets armed wih complex 

 points and the legs provided with hooks, all of which leads one 

 to predict that a renewed search will discover some kind of 

 sperm-receptacle in these crayfishes. In that event the resem- 

 blances that led Faxon to call these crayfishes Ca^nbaroidcs, as 

 being like Cambarus^ would be strengthened in a way that 

 might add to the puzzling nature of the problem here presented 

 of close resemblances between animals in the eastern and west- 

 enr areas of the continents. North America and Eurasia along 

 with generic differences between the east and west of each con- 

 tinent. 



Having shown that in Ca7nbarus affinis the sperm put by the 

 male into the annulus will remain alive all winter and that the 

 eggs laid in the spring will develop if this sperm is present 

 till then, though they did not develop w^hen the annulus was 

 removed, it was concluded that the sperm-pocket of the annulus 

 was an essential link in the chain of reproductive organs, without 

 which Cambari would come to an end. 



To make way for a consideration of the possible mode of 

 origination of this peculiar organ, which seems to have no exact 

 homologue in other Crustacea nor in other animals, as it is an 

 unpaired, ventral, and not segmentally repeated organ, used 

 only for the storage of sperm, it seemed important to make more 

 sure that the annulus in all kinds of Cambari contained a sperm- 

 receptacle of the same nature. 



