24 T. KOMAT: STUDIES ON TWO ABERRANT CTENOPHORES 



importance. 



Gastro-vascularSystein. 



The mouth is situated in the centre of the ventral surface of the 

 body; it may however be more or less eccentric in situation in individuals 

 in which the halves of the body divided by the sagittal plane are 

 unequally developed. It presents itself as a small aperture of a roundish 

 shape. It leads dorsally into the pharynx (Pis. 2 & 3; ///') which is of 

 a depressed form, pronouncedly wider than high, and not elongate in 

 the vertical direction as in pelagic ctenophores. In the dorsi-ventral 

 view, the pharynx is roughly quadrate-shaped, often somewhat elongated 

 in the sagittal direction (PI. 2, figs, i, 2). But, in the horizontal sections, 

 the pharynx is of a shape like the letter H with the transverse bar of 

 H lying in the sagittal plane, the clefts in front and behind between the 

 lateral bars of H being produced by the proximal ends of the tentacle- 

 basis Avedged therein. As viewed in vertical sections traversing parallel 

 with the sagittal plase, the pharynx shows itself near the latter plane 

 like a depressed U (PL 3, figs, i, 2), but in places somewhat away from 

 there, as a pair of isolated chambers (figs. 3, 4), the transverse bar of U 

 being replaced by the proximal end of the tentacle-basis. 



This peculiar condition of the pharynx, so different from the 

 condition in ordinary ctenophores, is not to be considered as the result 

 of mere reduction of its vertical axis. As is clearly shown by the 

 development of the animal to be described later, the pharynx of the 

 larva is at first perfectly the same as that of ordinary ctenophores; but, 

 later it is sectiond into two parts, one situated dorsally and shorter in 

 length and the other placed ventrally and of the greater length; the 

 latter part spreads out into the body skirt, while the former persists as 

 the pharynx of the adult animal. Hence, the pharynx of the adult is 

 merely a part of the original larval pharynx. In relation with this 

 peculiarity of the pharynx, there are several characteristics to be found 

 with respect to the arrangement of the canal system. 



The wall of the pharynx shows a large number of conspicuous 

 folds disposed largely ])arallel with the sagittal plane of the body (Pi. 2, 

 figs. I, 4; PI. 3, figs. 1-4, ?>; ph. f). The folds are divided into four 

 interradially placed subequal parts by two furrows that lie in the 

 two perradial planes of the body. 



As the development just mentioned already suggests, the epithelium 



