384 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



impossible, as I have found spermatophores with and 

 without the head in the same spermatheca or in the two 

 spermathecae of the same individual. I shall refer to 

 this again later. 



The minute structure of these spermatophores has 

 been described by Vejdovsky (1884), and by Lankester 

 (1871, a). When examined in transverse section, the 

 spermatophore is seen to be circular in outline. In the 

 centre is a cavity which we will call the axial cylinder 

 (PI. VII, figs. 51 and 52, ax.c). It extends from end to 

 end of the spermatophore, and even into the conical head. 

 It is widest in the centre, and tapers off at both ends. 

 This cavity is filled with a substance which, when the 

 spermatophore has just been liberated from the worm, is 

 granular in appearance. This central mass stains deeply 

 with borax-carmine, and in permanent preparations has 

 the appearance of a mass of longitudinal fibres, which 

 usually become somewhat shrunken by the action on them 

 of reagents. Outside the axial cylinder is a very narrow 

 dark band, which stains much more deeply than the 

 substance of the axial cylinder (PI. VII, figs. 51 and 

 52, sm. h.). For this reason it is very conspicuous. When 

 highly magnified it is seen to consist of a very large 

 number of minute oval masses, which, owing to their 

 staining properties, I conclude are the heads of the 

 spermatozoa. The rest of the spermatophore is made up 

 of a cementing material in which the tails of the sperma- 

 tozoa are embedded (PI. VII, figs. 51 and 52, sra. t.). As 

 was pointed out both by Vejdovsky and Lankester, these 

 are placed parallel to one another, but obliquely to the 

 axis of the spermatophore. The tails of the spermatozoa 

 appear as striations in the homogeneous substance in 

 which they are embedded, and when viewed from the 

 surface are seen to pass obliquely round from left to right. 



