90 T. KOMAT : STl^DIES ON TWO ABERRANT CTENOPHORES 



features that pharynx is thrown into numerons folds, that the oesophagus 

 is differentiated well, as also that the infundibular canal is obliterated, 

 are recognizable in various degees in all the members of the group. 

 Besides, except in Gastrodes, excretory canals show no branching and 

 pharyngeal canals are wanting. 



In Coeloplana, eggs develop in a linear tract from each of the 

 eight canals that represent the meridional canals of ordinary ctenophores, 

 while sperms arise in a certain number of separate masses along the 

 same canals. In Ctenoplana, eggs have not yet been found, but sperms 

 are known to develop in compact masses much as in Coeloplana, and of 

 the masses, there occurs but one to each canalar pouch, there being in 

 all four masses in each individual. In Tjalfiella, both eggs and sperms 

 develop on the wall of the aforesaid eight diverticula of the perradial 

 canals, the sperms on the interradial, and the eggs on the perradial 

 side of each diverticutum. In Coeleplana and Ctciioplana, the sperm- 

 masses are provided with ducts for the passage of the sperms to the 

 outside. In Gastrodes, the sperms have not been observed as yet, the 

 eggs are found scattered in the ventral epidermis. In Jjalfiella and 

 Coeloplana, the larval stage is perfectly like a cydippid and provided 

 with comb-plates. 



In view of such points uniting the four genera together or 

 distinguishing them from one another as mentioned above, it seems to 

 be reasonable to arrange the genera under a common group and erect 

 it as a separate order under the class Ctenophora, as it has been done 

 by previous authors. And we may give the diagnosis of the order 

 Platyctenea somewhat as follows : — 



" Creeping, sessile or parasitic Ctenophora. Body flattened, pre- 

 senting distinct dorsi ventral ity as the result of the out-spreading of 

 the external part of the pharynx. Comb-plates may be wanting in 

 adult. Colourless or brightly coloured. Gastro-vascular canals generally 

 branching. Tentacles of cydippid type, sometimes rudimentary". 



Regarding the relationship of the Platyctenea to other orders of 

 the Ctenophora, it is without doubt that there is a direct and close 

 consanguinity between the order and the Cydippidea. This is especially 

 clearly shown in the development of Coeloplana and Tjalfiella. Further, 

 the compression of the body, with the transverse axis longer than the 

 sagittal, is a feature common to the two orders and differentiates them 

 from the remaining. Similar fact may be said with respect to the 

 tentacular apparatus; it is only those two orders that arc provided with 



