340 ARTHUR WILLEY. 
glossus and many other such like theories, which at the time 
no doubt appeared to be logical necessities, will be quite ruled 
out of the field of possibilities. 
The descendants of the Archiplanoidea have no ccelom and 
no preoral lobe. The descendants of the Cerianthide have a 
celom and also a proral lobe (excluding the Anthozoa). 
It is an interesting parallelism that the criterion for the 
antero-posterior axis, both in the Cerianthidze and in the 
Ctenophora (Thée paradoxa), was provided by what may be 
called a directive tentacle. It may, indeed, be something 
more than a mere parallelism. 
10. Summary of Principal Results.—(1) Discovery 
of one very distinct new species of Ctenoplana, and of another 
somewhat doubtful new species. 
(2) Observation of the movements and of the pinnate tenta- 
cles of the living Ctenoplana. 
(3) Accurate localisation of the pinnate tentacles. 
(4) Discovery of the double character of the circlet of sensory 
tentacles surrounding the otolith. 
(5) Discovery of the male genital organs and ducts of Cteno- 
plana, thus proving that Ctenoplana is an adult animal. 
(6) Description of the tentacle sheaths. 
(7) Account of the genital ceca of the gastro-vascular 
system, about whose walls occur the genital proliferations. 
(8) Chloragogenous tissue and gastric gland. 
(9) The tentacle axis of Ctenoplana corresponds to the longi- 
tudinal axis of Planarians, the stomachal axis of the former to 
the transverse axis of the latter, and the main axis of the 
former to the dorso-ventral axis of the latter. 
(10) The solid pinnate tentacles of Ctenoplana are not dis- 
posed bilaterally, but biradially. 
(11) The ctenophoral plates, gastric lobes, gonads, gonaducts, 
and aboral sensory tentacles are paired about the tentacle 
axis, 
(12) The aboral sensory tentacles of Ctenoplana are homo- 
logous with the polar plates (Polplatten) of Ctenophora, and 
with the nuchal tentacles of Polyclades. 
