386 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



described above, and that the oblique striations already- 

 referred to are caused by the tails of the spermatozoa 

 alone. 



It is very evident that the very characteristic form 

 of the spermatophores is dne entirely to the shape of the 

 spermathecal duct and its external aperture. The duct is 

 circular in section, so also is the spermatophore. During 

 the rapid movements of the worm it is very natural that 

 the spermatophore should be forced through the duct into 

 the wider pouch by a slightly spiral motion, and this 

 explains the oblique arrangement of the tails. The 

 muscular walls of the duct may also assist in forcing the 

 spermatophore into the pouch. As a rule, the first- 

 formed spermatophores, those which are forced into the 

 pouch soon after or during copulation, are pointed at both 

 ends or without the arrow-shaped head described above. 

 On the other hand, it is very usual to find that the 

 spermatophores which are formed last, that is, those 

 which lie partly in the duct and partly in the pouch, are 

 provided with the conical extremity. There can be little 

 doubt that the arrow-shaped head is moulded in that part 

 of the duct following directly on the external aperture, 

 for the shape of the two are exactly similar when the 

 spermathecal duct is retracted. I conclude, therefore, that 

 the spermatophores, moulded first in the spermatheca, 

 are forced through the duct and into the pouch quite 

 rapidly — partly by pressure from behind exerted by other 

 masses of spermatozoa and cementing material, and partly 

 by the contractions of the worm. At any rate, the 

 process would seem to be such a rapid one that the 

 spermatophore does not remain any length of time in the 

 duct. On the other hand, towards the close of copula- 

 tion, the formation of the spermatophores would take place 

 more slowly, and the posterior ends of the last 



