No. 2.] STRUCTURE OF BIMASTOS PALUSTRIS. 48 7 



apparatus after copulation. In Bimastos, and we must believe 

 the same of Criodrilus (4 and 10), the secretion must precede 

 copulation, and the latter consist of the transfer of charged 

 spermatophores from the male organs to the body wall of a 

 second individual, there to await final disposition. The whole 

 question of the mechanism and methods of copulation in earth- 

 worms is in an exceedingly hazy condition. 



The spermatophores of Bimastos are usually borne in pairs 

 upon the lateral regions of the body in front of the genital 

 openings, usually on somites XII or XIII. One worm may 

 bear as many as six. They bear some resemblance to the 

 spermatophores of Criodrilus, but are somewhat more complex 

 than is indicated by descriptions of that form. They are chiti- 

 nous club-shaped bodies, perfectly transparent, except the head, 

 which is white with contained spermatozoa. The upper por- 

 tion is curved and the base expanded into a disc for attachment, 

 as shown in the figure. The upper swollen portion contains a 

 cavity divided by curving transverse partitions into a number 

 of narrow chambers, or pockets, each gorged towards its blind 

 end with spermatozoa. 



The partitions do not extend quite across the cavity of the 

 spermatophore, so that there is a channel across the mouths of 

 the pockets by which they are in communication with the 

 exterior at the free end of the spermatophore, which is irregular 

 and ragged, and often shows a raveling out of the chitinous 

 filaments of which it is composed. The spermatophores are 

 very firmly attached to the cuticle, by what means I cannot 

 say, unless the granular cells of the prostate, whose function 

 is unaccounted for, may secrete a cement for this purpose. 

 The position of their orifices would suggest some such utility, 

 or perhaps the secretion of albumen for the cocoon. 



When the spermatophore is subjected to pressure, as under 

 a cover-glass, the spermatozoa float freely out, and therefore 

 appear to be unfixed in a cement substance such as is found 

 in the sperm-rope of Tubifex. In sections of the spermatophore 

 this point is obscure. 



Female organs. — The ovary is attached to the ventral por- 

 tion of the hinder surface of septum 12-13, and lies, as usual, 



