160 
mentioned. Enterogonia approaches the conditions met with in 
Discostylochus. One would hardly place these genera very close to 
Neostylochus on account of the dissimilarity in their copulatory 
organs, but a comparison shows, however, that within the family 
Stylochidae there are represented many different stages in the 
distribution of the eyes, which could easily be arranged into an 
excellent series, where the two extremities would be, on the one 
hånd, Neostylochus pacificus, and on the other Idioplana, as well 
as a number of Stylochus-spQcies without frontal eyes. When one 
notices how very small, even-sized, and scarcely differentiated the 
ocelli, dotting the entire anterior end of Neostylochus pacificus, are, 
one is apt to assume that this is the more primitive organization. 
However, the presence of tentacular eyes in Neostylochus contradicts 
the idea that the arrangement of the eyes in its entirety might be 
primitive. The small tentacular protuberances with specially differ¬ 
entiated epithelium and with underlying larger ocelli indicate the 
inheritance from ancestors with better developed tentacles. Under 
such circumstances one should perhaps for the present assume a 
critical attitude toward the interpretation of the diffusion of ocelli 
over the anterior end and the absence of distinet cerebral eye- 
groups as a primitive feature. One is, morcover, entitled to this 
attitude, as the arrangement of the eyes in Neostylochus fulvopunetatus 
shows likeness to that of certain species and may have 
been derived from common ancestors. Such a derivation seems 
further plausible because of the presence of distinet tentacular 
eye-groups with their better developed ocelli in the case of 
Neostylochus pacificus, and because all the genera that so far belong 
to the family Stylochidae possess superficial tentacular eye-groups. 
The genus Bergendalia, which I brought close to the family 
Stylochidae already in 1913, differs from the genera of this family 
in that tentacles are absenl and in the diffusion of the ocelli over 
the entire anterior end of the animal, even far back behind the 
brain. The description that Yeri and Kaburaki (1918) give of B. 
diversa does not remove these last obstacles for the classification 
of the genus with the family Stylochidae. However, 1 cannot omit 
pointing out again that only a thorough examination of a series of 
sections of the anterior end can definitely ascertain whether or 
not any traces of tentacle rudiments or tentacular eye-groups are 
