48 NOTES ON THE ANATOMY OF DINOPHILTJS. 



just alluded to (cf . fig. 3)^ and occupy a large proportion of the cavity 

 of the fifth segment. 



The connection between the testis and the vesiculse seminales is 

 by no means easy to discover in sectionsj but can be best made out 

 by careful compression of the living animal. Under these condi- 

 tions, it may be observed that the anterior end of the vesicula semi- 

 nalis is quite closed, and that the communication with the testis is 

 effected by the agency of a ciliated funnel^ which passes forwards 

 from the posterior end of the vesicula, and somewhat from its ventral 

 surface, to open into the posterior median region of the testis (fig. 

 15). This region is reduced to a narrow space between the two 

 vesiculae seminales (and therefore ventral to the intestine) during 

 the condition of full distension of these structures by spermatozoa. 



The funnel and the adjoining part of the inner wall of the vesicula 

 are ciliated, but I believe that cilia do not occur in all parts of the 

 latter. The vesiculse seminales never contain unripe spermatozoa, 

 although mature, actively moving spermatozoa are to be found in 

 the cavity of very young and small vesicula, even when no such 

 spermatozoa could be seen in the testis itself. This implies that 

 the spermatozoa tend to make their way to the posterior part of 

 the testis as soon as they become ripe. 



It is perhaps worth while to mention that the above account of the 

 communication between the testis and the vesicula seminalis has 

 been confirmed, in its general features, by the study of sections. 



The fully developed vesiculse seminales are regularly ovoid in form, 

 with their principal axes parallel to the main axis of the body of the 

 animal. The posterior pole of each vesicula passes into a very obvious 

 duct, which opens laterally into the sheath of the copulatory organ. 

 The generative pore is a median structure, situated on the ventral 

 side of the base of the tail, a little posterior to the level of the anus 

 (figs. 3, 15). The pore opens into a vestibule, into which projects 

 the extremity of the penis. This organ is embedded anteriorly in a 

 solid glandular mass of cells, and consists of two parts. The first 

 of these is composed of very distinct cells, of a glandular appear- 

 ance, and staining very deeply with carmine or haematoxylin. These 

 cells radiate in a single layer from the internal cavity of the organ. 

 The second part of the penis projects into the generative vestibule, 

 and consists of a series of narrow, spike-like rods (in which nuclei 

 could be distinguished), which, lying side by side, form a truncated 

 cone, open at its extremity^ and continuous with the cavity of the 

 penis. 



A copulatory organ of the same general character as that above 

 described is well known to occur in the dwarf males of D. gyrociliatus 

 (Korschelt, Repiachoff, &c.), whilst from a figure (plate viii, fig. 7) 



