STRITCTURE AXD nF.VlCI.OPMENT OV C(-)EI.OPLANA. 5 



description of C. bocki, a third species occurring plentifully in the waters 

 near Misaki, giving at the same time a short sketch of its development 

 which he was able to study. In the same year, another new species, 

 C. gonoctena, was described by Krempf ('20, a-c, '21) from Annam, 

 with a series of works on the structure and development of the animal 

 published during the }'ear and the next. 



Turning oiu" attention to other forms which evidently stand in 

 close relationship to Coeloplana, there come into question the three 

 genera, Ctenoplana, Tjalfiella and Gasirodes. 



Ctenoplana was first described by Korotneff ('86) from the eastern 

 coast of Sumatra, and afterwards by Willey ('96) from the Eastern 

 Archipelago of British New Guinea. It is represented by three species, 

 namely, C. kowalevskii Korotneff, C. korotneffi Willey and C. rosacea 

 Willey. In both external and internal features they bear a far-reaching 

 resemblance to Coeloplana, but differ from this, above all, in being 

 furnished with comb-plates by means of which Willey's specimens were 

 observed to swim. 



Tjalfiella {T. tristoma) is a very singular animal which was des- 

 cribed from the western coast of Greenland by Mortensen. ('10, '12, 

 a-c). It is sessile in habit, and is in external appearance very unlike 

 any of the genera mentioned. It has been made clear that the species 

 passes through a typically cydippid larval stage. 



Gasirodes {G. parasilicum), finally, is a parasitic animal living in 

 the body of Salpa. It was discovered in 1888 by Korotneff, who 

 regarded it at first as a narcomedusa but afterwards as an actinian ('91), 

 whereas, Heider ('93) referred it to the Ctenophora. Recently ('20, b) 

 the present author has shown that it is distinctly a ctenophore evidently 

 to be assigned to the same group as the three genera mentioned above. 



As to the name given to the group. Bourne ('00) introduced 

 "Platyctenea ", which was adopted by most of subsequent writers either 

 without or with an alteration in the ending of the word.''' 



Material and Methods. 



The material which formed the basis of this study were all secured 

 in the littoral of Misaki mostly by myself at several occasions during 



* "Platyctenida" or "Platyctenidae". For the same group the term '• Archiplanoidea'" 

 was proposed l)y WiLLEY ('96); but this is not preferable, since it conveys a somewhat inadequate 

 conception about the systematic position of the group. 



