154 
there is merely the question of an alteration of the very same 
original type. The differences are thus of no fundamental nature, 
which is an imperative necessity for the genera of the same family. 
Returning to the ductus g. i., it could be pointed out that, in 
the present case, its role for the transfer of a surplus of sperma 
seems less important. Enterogonia has acquired no special reservoirs 
for the accumulation of sperma in a larger mass. Thus we can 
hardly expect that the female apparatus at the same copulation act 
receives an excessive amount of sperma. In full accordance with 
this view we find the ductus vagino-intestinalis short and narrow. 
The absence of any special adaptation for the reception of injected 
sperma harmonizes thus very well with the simplicity of the male 
organization. In Discostylochus^ where the ductus vagino-intestinalis 
has a far better development (compare chapter II of „Planarians 
I—111“ of this series) we meet with a highly specialized male organi¬ 
zation, showing both a pair of large seminal vesicles and a prostatic 
vesicle of a considerable dimension. 
There is in Enterogonia perhaps mainly a utilization of super- 
fluous material coming from the uteri. For the transmittance of it 
to the intestine the ductus g. i. might as well have a very simple 
structure. My observations of eggs in the alimentary system, as 
related above, indicates that the duet has such a funetion. 
The arrangement of the eyes within the family Stylochidae. 
The eyes and their arrangement in Stylochidae deserve a special 
discussion. It is important that the attention is focussed on them 
to a greater extent than has formerly been the case. On account 
of the abundance of the ocelli, as well as their small size, most 
descriptions lack exact diagrams of the distribution of the eyes. 
Unfortunately there is frequently only a small paragraph in the 
text or else indications on the small-scale reproduction of the entire 
animal. Obviously such brief treatment is unsatisfactory and cannot 
be mueh useful in systematic studies. In this connection it should 
also be mentioned that an ordinary lens-magnification is not suffi¬ 
cient, but that a microscopic examination of well-preserved specimens 
is necessary, in order to discover the often minute marginal ocelli. 
The marginal eyes located further back in the body are particularly 
difficult to discern, because they are frequently extremely small, 
