CTENOPHORA. 



dermal origin of the genital cells. That I have found nothing in Tjalfiella, which might suggest a 

 wandering of primordial genital cells from the mesoderm into the genital organs, is, of course, not 

 sufficient evidence against such theory; but I fail to see, how a figure like PI. VI, fig. 5, could be ex- 

 plained otherwise than I have done, viz. that it shows directly the germinal cells originating through 

 a proliferation of the entodermal epithelium of the genital cavity. Schneider also admits that (in 

 Beroe] "an den lateralen Randpartien der Gonaden die Abgrenzung keine iibermassig scharfe ist" (Op. 

 cit. p. 393). Further, when he adduces the observations of Willey on the genital organs of Cteno- 

 plana as important supports of his view, this loses a good deal of its weight from the fact that 

 several severe objections may be raised against Wil ley's work, as shown below. Schneider's 

 view (Op. cit. pag. 395) of "die aufsteigend morphologische Differenzierung" of the genital organs in the 

 Ctenophores, four "Differenzierungsschritte" being distinguished, starting from Porifera, seems to me 

 in consequence rather ill founded. For my own part I cannot doubt the correctness of Chun's 

 view of the entodermal origin of the genital cells in Ctenophores. 



In the preliminary description of Tjalfiella I have stated that the genital organs have external 

 ducts as in Ctenoplana. A closer study of the sections has proved that such is not the case; the 

 ripe sexual products, as shown above, fall directly into the gastro vascular system (the 

 genital cavity) in the same way as in other Ctenophores. The supposed genital ducts 

 are only ectodermal in vaginations, sacs which are quite closed towards the genital 

 organs and separated from them through a thin layer of mesodermal tissue. (Comp. 

 PI. IV, Fig. i; PI. V, Figs. 6 7, 1213; PI. VI, Fig. i and especially PI. VII, Fig. n). In the bottom of 

 the sacs there is an elevation, like a knob; this elevation limits one side of the bottom of the sac, 

 which is clad with a high epithelium, in which cell limits appear as rather distinct radiating lines. 

 The nuclei are arranged partly in a nearly regular layer along the outer edge, partly and more irre- 

 gularly along the basal edge of the epithelium. These cells are provided with long cilia 

 (PI. VII, Fig. n). The other part of the bottom of the sac is lined with simple, low epithelium which 

 continues some way up along the outer side of the elevation which limits the ciliated part. The walls 

 of the duct through which the sac opens to the exterior are of the same structure as the outer epi- 

 thelium, with rather numerous gland-cells. The opening may be of very different width ( comp. e. g. 

 PI. VI, Fig. i, i. with PI. VII, Fig. n); it may then not be unreasonable to suppose, that it can be 

 actively closed or opened by means of the muscles extending into the lips of the opening (PL VII, 

 Fig. 11). 



It appears evident that these peculiar organs cannot have anything to do directly with the 

 genital organs, in spite of their position, one over each genital organ. That they must have some 

 kind of sensory function can scarcely be doubted - what function, it will be useless to 

 speculate over from the information available at present. They recall the invaginations over the 

 genital organs in Callianira bialata, to which they may possibly be homologous. The structure of 

 those sacs, however, appears to be less complicated than in Tjalfiella, but they are ciliated, the cilia 

 being "sogar in besonders grosser Anzahl vorhanden" in the sacs. (Her twig op. cit. p. 78). Chun 

 (Dissogonie. p. 95) also points out that "die characteristische Kornerstructur, welche die Driisencellen 

 der Coelenteraten und speciell auch jene der Ctenophoren anszeichnet, durchaus den Wimperzellen der 



