SIXTEN BOCK, TWO NEW COTYL. GEN. OF POLYCLADS. 27 



polyclads. I may here ref er to the cotylean genus P ericelis, 

 which posesses granular gland-cells in the epithelium of the 

 ductus ejaculatorius without any special vesicle being formed. 

 The description of ChromopJana makes it more easy to homo- 

 logize this part of the penis canal with the true prostatic 

 vesicle, as in that case, the only known example in the 

 Gotylea, the duct from the vesicula seminalis (the ductus 

 ejaculatorius) opens direct into the prostatic vesicle. If the 

 muscular wall of that vesicle of Chromoplana and its slight 

 lumen were reduced we would get the conditions prevailing 

 in Pericelis and in Amyellay which both lack a distinct pro- 

 static vesicle but still have kept the granular glands as 

 epithelial or subepithelial cells respectively. It may be re- 

 membered that both these positions of the granular gland- 

 cells are frequently met with in the polyclads, in most cases 

 in the same species. If this suggestion is right, as I have 

 every reason to believe, we have no difficulty to trace the 

 origin of the male apparatus of Amyella back to that of 

 Chromoplana, the latter being more primitive. It ought per- 

 haps to be pointed out that there are no real obstacles in 

 the rest of the organisation of these two polyclads to such 

 an assumption. The arrangement of the eyes in Chromoplana, 

 traced back above to the larval conditions of the Cotyleans, 

 even favours such an assumption. It was rather interesting 

 to obtain the latter genus, as this was the first cotylean 

 with a prostatic vesicle in which the seminal duct opens. I 

 may here men tion that another example of such a condition 

 was found by me in a new peculiar cotylean genus Boninia 

 from the Pacific (Bock 1922). 



To return to Amyella, the antrum masculinum is situated 

 in the closest proximity to the pharyngeal chamber. The 

 external male porus is not, as might be expected from the 

 anteriorly directed penis, situated in the anterior part of the 

 antrum but is placed farther back, in the closest vicinity 

 to the female porus. The apex of the penis in the position 

 of rest passes beyond the opening of the antrum„ Thus the 

 male porus comes to te situated at a farther distance from 

 the mouth than the approach of the male apparatus to the 

 pharynx would indicate. In this respect, but certainly of 

 less significance, we have a more primitive feature than in 

 Chromoplana, It must, however, be pointed out that this 



