94 Messrs. Hancock and Embleton on the Anatomy of Eolis. 



fact continued on in union with it to the bifurcation m, where it 

 separates from it as the smaller branch which goes on to the ex- 

 ternal genital orifice. 



In E. coronata, E. Drummondi and E. olivacea, the female 

 parts we have seen agree with those of E. papillosa ; the male 

 parts we have shown differ materially, and the androgynous ap- 

 paratus again presents corresponding modifications in these three 

 species. 



The spermatheca in E. coronata, fig. 3 A, is a simple elongated 

 pyriform sac without any accessory. 



In E. Drummondi it is a sacculated bag. The ducts connect- 

 ing the spermatheca, the oviduct and testis together in these spe- 

 cies have the same disposition as in E. papillosa, but the duct 

 which leads from the spermatheca to the external orifice is very 

 much modified. It begins externally by a large orifice leading 

 into a short wide channel with thick and wrinkled walls, figs. 3 & 

 4 j'f, into the side of a strong globular sac jj ; from the oppo- 

 site part of this sac issues a minute canal i' i', which returns 

 along the external wall of the wide channel, and approaching the 

 testis near its union with the oviduct, passes under it and be- 

 tween it and the penis, and then after a short tortuous course 

 backwards it unites with the duct of the spermatheca near i, a 

 little above, and not, as in E. papillosa, below, the junction of the 

 latter with the oviduct. 



The great size and peculiar modification of the external por- 

 tion of the channel just described has reference obviously to the 

 modified size and form of the intromittent organ in these species. 

 We feel little doubt that the penis passes along the wide channel 

 into the globular sac, which from its size and form is well-adapted 

 to receive and probably to retain the expanded extremity of that 

 organ. 



This part of the apparatus is then a peculiar vagina ; it is pos- 

 sible that a small point may be protruded from the orifice of the 

 penis, fig. 6 c, at the time of conjunction ; but whether this be so 

 or not, we believe that the seminal fluid is conveyed along the 

 minute channel, fig. 3 i! i', we have noted as passing off from the 

 vaginal sacj, and is thus delivered into the spermatheca h. 



Looking at the remarkable shortness of the testicular tube in 

 E. coronata, E. Drummondi and E. olivacea, in reference to the 

 modification of their copulative organs, we suppose that the de- 

 ficient development of the essential is compensated for by an in- 

 creased efficiency of the accessory organs, that a more prolonged 

 union of the sexes is here rendered necessary, and the conditions 

 for this we find in the peculiar form of the penis and the 

 vaginal sac. 



In E. papillosa, on the contrary, copulation is effected by the 



