stylochiis and Cryptophallus, we meet consequently with conditions 
which bridge over the gap between Stylochiis- and Ilyplana- 
conditions. 
The most striking feature in Ilyplana is undoubtedly the presence 
of cyanophile giands in the antral and penial wall. To this we have 
no correspondence in the previously described Stylochid-genera. It 
is, moreover, undoubtedly of interest to meet with just such giands 
in Plehniidae and Polyposthiidae, where I have described them in 
1913 and 1923. Ilyplana is a very good example of how important 
it is to gain an increased knowledge of the Polyclad-fauna in the 
Indo-Pacific for a right estimation of the Polyclad-system. Taking, 
for instance, the three European genera Discocelides, Cryptocelides, 
and Stylochus, we find that they are very distinet types. Polyposthia 
similis from Scandinavia and Plehnia arctica and japonica bring 
the two former nearer each other. The numerous Indo-Pacific 
genera of Stylochidæ contribute to the abolishment of the isolation 
of Stylochus. None of them, however, approach Discocelides so 
mueh as the Ilyplana from New Zealand, which also agrees with 
it in respect to oecological habits. Nevertheless, to connect them 
more closely is perhaps too early at present, as a great many 
dilferences could be enumerated and we need yet more conclusive 
finds. The interesting Plehnia japonica will gain in importance for 
the Polyclad-system after the description of a new genus from the 
South Sea Islands. It really seems to be unavoidable to establish 
a new genus also for Pi japonica. I wrote in 1923: »It would be 
easy to defend the placing of this new species in a separate genus«, 
but, in spite of that, I included it in Plehnia for the purpose of 
both emphasizing the relationship with PI. arctica and avoiding the 
establishment of a new genus with only a single species, if no 
imperative necessity for it existed. This manner of proceeding, 
at that time of advantage and hardly incorrect, can, however, not 
be upheld, when we are getting acquainted with new Pacific forms 
demonstrating relationships to both the Plehniidæ and Stylochidæ. 
Returning to Ilyplana and its relationships to Stylochidae, I must 
point out that the male organization perhaps most approaches 
that of Parastylochus and Cryptophallus. I attach then special weight 
to the prostatic organ. 
The same is true of the tentacular rudiments and, to a certain 
