306 CRK.S8WELI, 8HEARKK. 



the feet, and forward on the under side of the brain. It is 

 more or less separated from the cavity of the trunk by the 

 neck muscles and the narrow constricted condition of this 

 region. Its extension into the posterior feet is in free 

 communication with the trunk, so that in living- preparations 

 the eggs in the female can sometimes be forced into the leg 

 portion of the cavity V)y slight compression of the cover- 

 glass. 'J^liey slip back, however, to the main blastoccelic 

 space surrounding the gut when this pressure is removed. 

 The wliole of the blastocoelic cavity is very irregular in out- 

 line, and is divided, as has been described, in the trunk 

 region by the oblique muscle strands into two lateral 

 chambers. 



In evei'y respect it corresponds with the same cavity sur- 

 rounding the gut in Dinophilus. There is this difference, 

 however, that the numerous brown granules seen in it in 

 Dinophilus are wanting in Histriobdella, although 

 Histriobdella, like Dinophilus, has no specialised vascular 

 system. It is sharply divided from the sac of the ovary, 

 there being no communication between the two. When the 

 ova are forced into the blastocoelic space of the hind limbs 

 the sac of the ovary is either pushed with them, or is definitely 

 ruptured, and the ova pass directly into the blastocoele. Both 

 at the anterior and posterior regions tlie wall of the ovary is 

 considerably thickened where it crosses the blastocoelic space 

 between the body-wall and the gut. In the male the sac of 

 the testis is likewise sharply cut off from the blastocoelic 

 space in the anterior and posterior part of the generative 

 region. Histriobdella, like Dinophilus, shows the primary 

 and secondary body-cavity existing together, but sharply 

 divided from one another. The nephridia, as in Dinophilus, 

 are in relation with the blastocoelic cavity alone. 



From the fact that we get two nephridia in the generative 

 region in the female, there is considerable reason for concluding 

 that the oviduct and its funnel can hardly represent a trans- 

 formed nephridium as Haswell has suggested. The ari-ange- 

 ment of the ganglia and the external appearance of the 



