ADDITIONAL L.M.B.C. TURBELLARIA. 169 



large seminal vesicle about twice as long as the pharynx, 

 and lying just posterior to it. It completely conceals the 

 atrium in pressure preparations, but the relations of the 

 various parts have been drawn from a section in fig. 8. 

 Here we see the penis projecting into the atrium ; and 

 the diverticulum which will afterwards form the seminal 

 receptaculum lying ventral and posterior to the seminal 

 vesicle. The testes are lateral, they extend forward to 

 the level of the seminal vesicle, with which they com- 

 municate by short ducts opening into the posterior end of 

 the vesicle. Posteriorly they do not quite reach back to 

 the middle of the body (fig. 3). 



The penis is very difficult to observe, but my examina- 

 tions of pressure preparations which I have been able to 

 confirm by sections shew it to be a short thick tube, 

 strengthened by several cuticular rings and capable of 

 being retracted so as to appear as a rosette shaped organ 

 on anterior end of seminal vesicle (fig. 10), or of being 

 protruded as shown in figs. 11 and 13. The distal rings 

 appear to be provided with fine serrations. I have not 

 been able to make out the mechanism by which the penis 

 is thus protruded. 



In large individuals, in which the female organs are 

 fully developed the testes and seminal vesicle together 

 with the penis have atrophied and cannot be found either 

 in pressure preparations or in sections. In one or two 

 lucky pressure preparations I had the good fortune to find 

 the seminal vesicle persistent, and the testes still visible ; 

 in these specimens the germ glands were not mature, and 

 the yolk glands were much less extensive than in the 

 majority of cases. 



In the typical " female " condition the receptaculum 

 seminis is large, spherical, and lies dorsal and posterior 

 to the atrium (figs. 4 and 12) which is provided with uni- 



