ON OTENOPLANA. 331 
opening to the exterior in six. In another individual I counted 
seven ducts altogether. 
It should be added that the above description of the male 
gonads applies exclusively to C. Korotneffii, all three speci- 
mens of which possessed them. 
7. Axial Relations—Comparison of Ctenoplana with 
Planaria and Ctenophora.—As already known from the 
work of Korotneff, Ctenoplana agrees with the Ctenophora 
in the possession of a main axis(Hauptachse) which connects 
the aboral pole with the oral pole, the mouth with the sense- 
organ, and that this main axis forms the line of junction of 
the two principal planes—namely, the tentacular plane and 
the stomachal plane. 
Ctenoplana presents remarkable Planarian affinities in re- 
spect of its dorso-ventrally flattened body, in the possession of 
a definite dorsal surface, and a definite ventral or locomoter 
surface, in its habit of creeping, and especially in its habit of 
attaching itself to the surface-film of water. This enumeration, 
to which may be added the partial ciliation of the ectoderm, 
nearly exhausts the list of its strictly Planarian affinities. 
Besides the coincidence of the main axis and principal planes 
of Ctenoplana with those of the Ctenophora, the chief points 
of affinity are the possession of two pinnate tentacles which are 
each retractile within a sheath, the possession of the eight cteno- 
phoral plates, and the presence of the median funnel vessel. 
The two series of sensory tentacles placed on opposite sides 
of the otolith, whose epithelium is directly continuous with 
the epithelium of the cupule of the otolith, are directly com- 
parable with the polar plates (Polplatten) as described by 
Chun in the Ctenophores. In the first place they agree with 
the latter in lying in the stomachal plane, in so far that they are 
paired about the tentacle axis. This is the most important 
point of agreement morphologically, but they also agree in 
1 According to the remarkable observations of Chun, some Ctenophores 
possess this power, effecting it by spreading out the wall of the stomach,— 
sometimes, as in Lampetia Panceri, nearly everting the stomach as far as 
to the origin of the peripheral vessels. 
