184 E. A. ANDREWS. 



lines, had been pulled. Thus, here, as elsewhere the shell- 

 pocket shown in Fig. 12 is cast in an epidermal mould of like 

 form, a mould that exists as an epidermal groove. The epider- 

 mal groove secreted so thick a shell as to fill up the groove, all 

 but a narrow slit, and it is this narrow cavity that doubtless is 

 filled with sperm by the male, though in this single specimen no 

 evidence of sperm was found. 



A cross-section of this sperm-pocket would be essentially 

 like Fig. 8. 



From this one female it is impossible to say whether this 

 species is dimorphic or not, but one may confidently predict 

 that an examination of many specimens would show that there 

 are both right- and left-handed forms. Some would have the 

 sperm-pocket the mirror image of that shown in Fig. 12, so that 

 these females would have the suture reversed and the pocket 

 inclining the opposite way at each turn, as compares with 

 Fig. 12. 



We have thus -demonstrated that the same sort of sperm- 

 pocket is found in these two crayfishes, Cambarus cubensis and 

 Cambarus paradoxus, as in all other species of Cambarus yet 

 examined and have now found the same essential structure in 

 the annuli of representatives of all the six subgenera of Cam- 

 baruS) so that the sperm-pocket may be regarded as the funda- 

 mental feature of the annulus of all the Cambari. 



SUMMARY. 



The sperm-receptacles found on the ventral surface of the 

 lobster and of the crayfish of the genus Cambarus are not 

 homologous with one another, though they have the same use 

 and location. In the lobster the receptacle is an external space 

 covered over by the annular plate of the seventh thoracic somite ; 

 in Cambarus the receptacle is a narrow pocket invaginated into 

 that same annular plate. 



It is shown that in each of the six subgenera of Cambarus 

 the annular plate contains the same sort of pocket and hence it 

 is most probable that sperm is stored up in such pockets in all 

 species of Cambari. 



