CTENOPHORA. 



27 



noticed in the inner anatomical strncture between Tjaljiclla and Ctenoplana. But tliere would seem 

 to be other important differences. 



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

 by the possession of a pair of pecuHar "gastric glands" and some not less pectiliar "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 *" 



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. ca. genital CEecum; ch. "chloragogenous cells" 

 (= colloblasts); cil. ciUated 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 proUferation on the wall of the genital 

 caecum '; g. p. "gastric proliferation" ; mes. niesenchymatous tissue; 

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

 cihated glandular epithelium of the ventral surface. 



