No. I.] SPHYRANURA OSLERl. 37 



tacula seminis, the overflow-tube to the intestine (on the same 

 side as the ovary), and the uterine tract of the oviduct. 



We have referred above to the position of the testicular 

 lobules between the intestinal branches. Fig. 14, which illus- 

 trates half of a transection through the middle of the body, 

 shows well the relation of such a lobule to the intestine and 

 vitellogen. Near the anterior end of the testicular area the 

 vas deferens can be made out near the middle line of the dorsal 

 surface (v. d.), but the short tubes which lead from it to the 

 lobules, and the more posterior parts of the vas deferens itself, 

 do not exhibit the same epithelial lining which may be detected 

 anteriorly. 



Occupying the same position towards the dorsal surface as the 

 vas deferens, its anterior end or ejaculatory bulb exhibits little 

 difference except in regard to size and to musculature. When 

 filled with sperm it is very often strongly curved to one side 

 (Fig. i), and in such conditions forms a very prominent feature 

 in the Sphyranura, viewed as a transparent object, on account of 

 the opacity of the sperm. W^hen the bulbus arrives nearly to the 

 level of the anterior arch of the intestine it changes its course, 

 running directly towards the ventral surface to its aperture in 

 the genital sinus. (Fig. 16, b,e?) In this part of its course it is 

 suddenly constricted before being expanded into the terminal 

 globular part, which is crowned with a circlet of spicules, and 

 which can be everted into the genital sinus, if not out of the 

 external aperture thereof While the main part of the bulbus 

 is merely provided with circular muscular fibres, this terminal 

 globular part or cirrhus is provided with longitudinal nucleated 

 fibres, whose duty is to evert the spicules, and thus open the 

 aperture of the cirrhus. Retraction and eversion of the whole 

 cirrhus is effected by specially modified parenchyma fibres, 

 which are only partly indicated in Fig. 16. In form the indi- 

 vidual spicules of the coronet closely resemble those of the 

 genus Polystomum. 



We now proceed to detail the results we have obtained as to 

 the structure of the testis, and the development and form of the 

 spermatozoa. 



The lobules of the testis number from twelve to fifteen, and 

 are of a different form, according as they are seen in transverse 

 or horizontal sections of the body. In horizontal sections they 



