S CTENOPHORA. 



the interstitial cells, the clear spaces by the mucous cells (PI. VIII. Fig. i). Among the common 

 cilia are found some coarser bristles, not exceeding the cilia in length ; I think there can be no doubt 

 that thev represent the sensor)- bristles so generally met with in Ctenophorans, though they are shorter 

 here than usual. (Comp. e.g. Samassa. Op. cit. Taf. VIII. Fig. 14. Hertwig. Uber den Ban der 

 Ctenophoren. Taf. I. Fig. 5'). In any case I have not been able to discern them as being composed of 

 agglutinated cilia with the highest magnifying powers at ray disposal. 



As stated above the lumen of the "chimneys" continues directly into the basal (or suborall 

 cavity; the longitudinal ridges of the chimneys also continue directly into the folds of the walls of 

 this cavity; they are, however, much less developed here than in the "chimney.s", and more reticulate. 

 On the contrary the roof of the suboral cavity is folded even to an extreme degree (PI. III. Fig. 11). 

 The histological structure of these folds is not essentially different from that of the ••chimney"-walls, 

 oiil\- the granular cells are much more abtindant. (PI. VIII. Fig. 3). 



Evidently the suboral cavity, and especially the folds hanging down from its roo'.f, 

 has undertaken the functions of a stomach; the absorption of the food takes place here, 

 whereas in the typical Ctenophorans it is the pharynx which has this function, the true (entodermal) 

 stomach (the "infundibulum"), generally not receiving the food material directh-, onh' the chymus^i. 

 In the middle of these digestive, circumoral folds the true mouth opening is found; it has 

 the shape of a narrow slit, being in the sagittal plane, viz. at right angles to the long (transverse) 

 axis of the body (PI. III. Fig. 11,0). It is only seen on pushing aside the folds, by which it is normally 

 covered. It leads into a short pharynx which, as appears from the section represented in PI. IV. Fig. 4, 

 is compressed in the sagittal plane as usual in Ctenophores. The walls of the pharynx are densely 

 ciHated and contain only few granular and gland cells (PL VII. Fig. 2). At its upper end the pharynx 

 opens into the very low infundibulum (stomach), the aboral wall of which consists of a low epi- 

 thelium with the nuclei arranged in a single layer, and which is apparently not ciliated. The apical 

 organ lying close to the aboral wall of the infundibulum there is no room for an infundibular canal 

 ("Trichtergefas.s"), and the excretory vessels therefore originate directh- from the infundibulum (PI. VII. 

 Fig. 1). There are two simple excretory vessels, lying on each side of the apical organ in the sagittal 



') Quotedfroiu the separate edition; in Stiidien zur Blattertheorie, von C). Hertwig u. R. Hertwig. HeftUI. Jena 1S80. 



2) I cannot accept the terminology adopted by C h n n. .\s shown definitely by the development the part which he designates 

 as "Magen" is of ectodermal origin, and accordingly represent.s the pharynx (or stoniodjeiun); the true stomach, of ento- 

 demial origin, is the infundibulum, or as he names it, "Trichter". To speak of a "primary" and "secondary" Entoderm, as 

 does Chun (Ctenophoren des Golfes v. Neapel. p. 117), does not alter the fact that the part of the gastrovascular system which 

 he terms stomach is really of ectodermal origin. What has caused this unfortunate terminology is doubtless the fact that 

 the pharynx has undertaken more or less completely the function of absorbing the food. But if this is accepted as a valid 

 reason for designating the pharynx as the stomach we should consequently also name the basal or suboral cavity of TjalfieUa 

 the stomach — but as this cavity is really outside the mouth, I think nobody would accept that terminology. (In most of 

 the recent text-books the terminology of Chun is justly rejected). We must acknowledge the fact that in the Ctenophorans 

 the function of absorbing the food has been transmitted from the stomach to the pharynx, and in Tjalfirlla even to the 

 folds outside the mouth. 



In the young BoHna Chun (Die Dissogonie; Festschr. f. Leuckart. p. 9S) has found the Entoderm-cells of the meri- 

 dian vessels "mit festen Nahrpartikeln erfuUt, welche sie intracellular verdauten. Partikel des Chitinskelettes von Krustern 

 und Bundel quergestreifter Muskeln waren oft so reichlich in ihuen aufgespeichert, dass man auf Schnitten durch die Zwitter- 

 gefasse der Jugendformen ganz fremdartige und verwirrende Bilder erhielt". Likewise Abbott (The Morphology of Coeloplana. 

 Zool. Jahrb. Abt. f. Anat. Bd. 24. 1907, p. 54) records that in Coeloplana "In the peripheral region (of the gastrovascular system) 

 various metaplastic bodies become very evident: globules of fat, ... In addition all varieties of ingested food matter may be 

 found, such as diatoms, as well as other foreign bodies, apparently half digested". These obser\-atinns show that it is, however, 

 no unexceptional rule that the pharynx of Ctenophores has undertaken the absorbing function. 



