153 
with a nearly similar feature. The development of false seminal 
vesicles of Cryptophallus and Parastylochus forms a substitute for 
the missing unpaired true seminal vesicle. In the place of this 
latter we have, anyhow, the ejaculatory duet. In regard to the 
matter under consideration the new genus Leptostylochus forms an 
interesting intermediate link between the Cryptophallus-, Parastyl¬ 
ochus-, Discostylochiis-iypc and the Enterogonia, There the acquisition 
of a special musculature for a part of the seminal canals has not 
progressed further than to show a local strengthening. Furthermore, 
in Kaburakia, also described here, we meet the last type in the 
Chain; that is, neither true nor false seminal vesicle in strict 
sense, but a combination of the two. Thus the discussion has 
given'evidence that nothing in the male apparatus argues against the 
joining of the genus to Stylochidae, while at the same time the 
presence of the prostatic vesicle is full proof that my assertion is 
correct. 
Leaving the ductus genito-intestinalis out of consideration, there 
is in the female organization no hindrance for the classification 
of the genus with the Stylochids. It might be mentioned that such 
a feature as the spiral epithelial ridge of the shell duet is also 
met with in some of the Stylochid genera, as discussed above. 
Since we thus have been able to rank Enterogonia in Stylo- 
chidcp, it is of considerable interest that also the ductus genito- 
intestinalis is previously known in the family, being present in 
Discosty lo chus parcus from Hawaii, described in the second chapter 
my paper: Planarians I-IH of this series. In both cases the duet 
is the very same kind of formation; i. e. a ductus vagino-intestinalis. 
The question could then arise if we are entitled to unite the 
two genera, Enterogonia and Discosty lo chus. On account of the 
pronounced dissimilarity of the prostatic vesicle and also the oceur- 
rence of well-differentiated false vesiculæ seminales in the latter 
genus as well as some other differences, I must consider it 
necessary to maintain the two genera as separate. The divergencies 
of the male apparatus are, however, not of such an importance as 
to exelude the ranking of them fairly near each other. The for¬ 
mation of vesiculæ seminales and the progressive and regressive 
evolution respectively of the prostatic vesicle in the Stylochidæ are suffi¬ 
ciently discussed below to bring evidence also for the present case that 
