CTENOPHORA. 



c.f. 



noticed in the inner anatomical structure between Tjalfiella and Ctenoplana. But there would seem 

 to be other important differences. 



According to Willey's description the gastro vascular system of Ctenoplana is characterized 

 by the possession of a pair of peculiar "gastric glands" and some not less peculiar "gastric 

 proliferations" from the walls of the terminal gastric lobes; the cells of these proliferations "appear 

 to assume the properties of chloragogenous cells, and numerous yellowish refringent concretions 

 occur in and amongst them" (Op. cit p. 330). (Comp. the fig. 5 of Willey's paper, here reproduced 

 in fig. 4). It appears to me beyond doubt that these "terminal gastric lobes" are the tentacle 

 vessels, their lumen being lined with large, clear entoderm cells, as in Tjalfiella a. o. Ctenophores. 

 The supposed chloragogenous cells ..to. 



are the colloblasts of the thickened 

 tentacle base ( which may, indeed, well 

 recall chloragogenous cells ). Quite the 

 same evidently is the explanation of the struc- 

 ture thus described by Korotneff (p. 244): 

 "Au einer Seite des Tentakels befindet sich 

 eine feinkonige, vielleicht driisige und sich 

 stark farbende Bildung; die andere Seite 

 besteht aus einem schwammigen Gewebe". 

 (Comp. Fig. 3). The "gastric gland" is thus 

 described by Willey (p. 330) "As the median 

 walls of the neighbouring terminal lobes fuse 

 together on nearing the median canal which 

 connects them with the stomach, the minute 

 cellules which compose the greater part of 

 the proliferations in question are replaced by 

 long pyramidal cells which compose a com- 

 pact gland, having a radiating structure due 

 to the peculiar arrangement of the cells. I 

 will call this a gastric gland, and hope 

 that at some future date light may be thrown 

 upon its nature". I think I am able to throw 

 the light wanted upon this peculiar structure; though no figure is given of it, the description seems 

 to me to leave no doubt but that it is only the tentacle-base, the radiating structure being due 

 to the arrangement of the muscles in the tentacle-root 



After this explanation of the two supposed peculiar structures of the gastrovascular system of 

 Ctenoplana, it is evident that there is a very close similarity between Ctenoplana and Tjalfiella, also 

 in the gastrovascular system, the only difference of greater importance being the absence of the sagittal 

 lobes in Tjalfiella. (The absence of anastomoses between the peripheral canals in Tjalfiella can 

 scarcely be a character of primary importance). 



4* 



Fig. 4. Sagittal Section (somewhat oblique) through | Ctenoplana, 

 reproduced from Willey, Op. cit. PI. 21, fig. 5. The letters are 

 those of Willey. ess. genital caecum; ch. "chloragogenous cells" 

 (= colloblasts) ; cil. ciliated epithelium of ventral surface; c. p. 

 "Ctenophoral plate" (= costal, retracted; d. e. dorsal spongy vacu- 

 olar non-ciliated epithelium; ent "coelenteron"; ep. digestive epi- 

 thelium; gen. "genital proliferation on the wall of the genital 

 caecum"; g. p. "gastric proliferation"; mes. mesenchymatous tissue; 

 to. opening of tentacle sheath; t. s tentacle sheath; v. e. non- 

 ciliated glandular epithelium of the ventral surface. 



