CTENOPHORA. 



27 



noticed in the inner anatomical structure between Tjaljiella and Cienoplana. But there would seem 

 to be other important differences. 



According to Willey's description the gastrovascular system of Ctcnoplana 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). (Conip. /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 

 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 imd 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 b}' 

 long pyramidal cells which compose a com- 

 pact gland, having a radiating striTcture 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 



Fig. 4. Sagittal Section (somewhat oblique) through Ctcnoplana, 

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

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

 '= colloblasts); oil. ciUated epithelium of ventral surface; c. p. 

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

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

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

 caecum"; g. p. "gastric proUferation" ; mes. mesenchymatous ti.ssue; 

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

 cihated glandular epithelium of the ventral surface. 



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 



Ctcnoplana, it is evident that there is a very close similarity between Ctcnoplana 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 Tjaljiella can 



scarcely be a character of primary importance). 



4* 



