8o T. KOMAI : STUDIES ON TWO ABERRANT CTENOPHORES 



(figs. 3, 13), while it gives a roundish cross-section in smaller ones 

 (figs. 4-7). It is lined with the epithelium of the ectodermfil origin, 

 which is identical in appearance with the ventral epidermis except the 

 ciliation being somewhat heavier. This passage represents, without 

 doubt, the oesophagus, a part of the stomodaeum which is recognizable 

 in all ctenophores but developed especially well in platyctenids (cf. 

 MoRTENSEN, 'i2; present paper, p. 25 et seq.). As mentioned above, very 

 young individuals lack the oesophageal opening. 



The oesophagus opens dorsally into the infundibulum (PI. 8, fig. 

 1 1 ; i), which lies directly under the aboral sense-organ. The infundibulum 

 is a relatively spacious chamber of a depressed shape, slightly wider in 

 the sagittal, than in the transverse direction. It is clothed all around 

 with a very low epithelium, which shows clear ciliation in the bottom 

 part. Perhaps the cilia exist in the epithelum of the roof too, but I 

 could not observe them in that region. The epithelium lining the roof 

 of the infundibulum is somewhat vacuolated. 



The infundibulum represents the source of the entire canal-system 

 of the body, which is arranged much in the same way as in ordinary 

 cydippid ctenophores. From each transverse side of the infundibulum, 

 there starts a perradial canal which runs obliquely oralwards and 

 communicates with the meridional, tentacular and pharyngeal canals, 

 just as in those ctenophores. A.11 of these canals are rather broad 

 relatively to their short length. 



The meridional canals (PI. 8, figs. 1-4, 1 1-14; in. c) are very broad 

 throughout their length especially in individuals of small sizes. The 

 pharyngeal canals (figs, i, 2, 13, 14; ph. c) are found only in large 

 individuals; they run along the transverse wall of the pharynx and 

 terminate nearly at the same level as the oral ends of the meridional 

 canals. The part of the body harbouring the pharyngeal canal is 

 often raised up on the ventral side of the body (fig. 14). The canal 

 has always a narrower calibre than the meridional canals. The tentaculer 

 canals (fig. 14, I. c) are very short but have the same structure as 

 those of the cydippids. The infundibulum further sends out an excretory 

 canal (fig. 12, ex. c) from each sagittal side of its wall. This canal 

 proceeds to the dorsal direction and opens to the exterior just outside 

 the sense-organ (fig. 1 1 , ex. p). The canal furcates into two branches 

 shortly previous to the opening, of which one branch opens to the 

 exterior, while the other terminates blindly in the surrounding tissue, 

 just as it is in ordinary ctenophores. In small individuals the gastro- 



