pace: anatomy of thersites bipartita (fer.). 207 



growth, which probably functions as a vesicula seminalis (v.s.), and the 

 epiphallus itself terminates in a minute caecum apparently representing 

 the flagellum (/.). The vas-deferens is closely applied to the free 

 oviduct throughout the entire course of the latter ; it then passes up 

 alongside the penis and enters at the base of the minute flagellum. 

 The vas-deferens is of unequal calibre, and its initial portion exhibits 

 slight sacculation. The inner wall of the eversible portion of the 

 penis for about a third of its length from the atrium is longitudinally 

 plicated, the plicae then become very much folded transversely, so 

 that the wall assumes an almost villous aspect over the second third. 

 A circular valve marks the commencement of the remaining third, 

 which is further differentiated by the presence of a strongly developed 

 muscular ' pilaster ' passing down from the retractor penis muscle 

 (with which, however, it is not continuous) to the valvular fold. The 

 epiphallar region internally is finely plicated longitudinally. 



