CTENOPHORA. 



the interstitial cells, the clear spaces bv 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 sensory 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 my disposal. 



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

 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 "chimneys", and more reticulate. 

 On the contrar>^ the roof of the suboral cavit>- 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, 

 only the granular cells are much more abundant. (PI. VIII. Fig. 3). 



Evidently the suboral cavity, and especiallv the fo'lds 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"), generalh not receiving the food material directly, only the chNuius^). 

 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 phar.\nx which, as appears from the section represented in PL IV. Fig. 4, 

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

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

 opens into the verv 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 caual 

 ("Trichtergefass"), and the excretory vessels therefore originate directh' from the infundibulum (PI. VII. 

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



') Quoted from the separate edition; in Studien zur Blattertheorie, von (). Hertwig u. R, Hertwig. Heft III. Jena 1880. 



2) I cannot accept the terminology adopted by Chun. As shown definitely by the development the part which he designates 

 as "Magen" is of ectodermal origin, and accordingly represents the pharynx (or stomodEEum); the true stomach, of ento- 

 dermal 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 dovibtless the fact that 

 the pharyux has undertaken more or less completely the function of absorbing the food. But if tliis is accepted as a vahd 

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

 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 TjalfifUa even to the 

 folds outside the mouth. 



In the young ISolina Chun (Die Di.ssogonie; Festschr. f. Leuckart. p 9S) has found the Eutoderm-cells of the meri- 

 dian vessels "init festen Nahrpartikeln crfiillt, welche sic intracellular verdauten. Partikel des Chitinskelettes von Krusteru 

 und Biindel cjuergestreifter Muskelu waren oft so reichhch in ihnen aufgespeichert, dass man auf Schuitten durch die Zwitter- 

 gefiisse der Jugendfonneu 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 evideiu : 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 observations show that it is, however, 

 no unexceptional rule that the phar\nx of Ctenophores has undertaken the absorbing function. 



