CTENOPHORA. 



There is no trace of costae and swimming plates. The animal is thus decidedl\- 

 unable to swim and must evidently rest for life on the Umbelhila on which it has fixed itself 

 as young. That it is capable of a slight creeping and gliding movement I think quite probable. The 

 epidermis of the surface is ciliated, with some sensory bristles occurring among the cilia, and besides 

 contains a number of mucus secreting cells; (the histological structure is upon the whole very like 

 that of the epidermis in the "chimneys"). In several of the specimens the basal surface was covered 

 by a thick layer of mucus. These facts seem to show that the animal cannot be fixed to the same 

 spot on the Umbellula, where it first took its place. On the other hand there is no special arrange- 

 ment of muscles in the basal disk. 



The epidermis of the outer surface of the body is quite smooth'), not ciliated, so far as I 

 have been able to see. Its histological structure does not afford any exceptional features. It contains 

 not very numerous, small gland-cells ("Kornercellen"). 



The apical organ is very simple (PI. VII. Figs, i — 2). It is a small groove, the walls of 

 which consist of a high epithelium, carrying long cilia, on which the statocyst is resting. I have been 

 unable to find any "balancers", and likewise the cilia do not appear to form a cupule over the statocyst. 

 There is no trace of polar fields, and there are no ciliated bands ("nerves"). Excretory openings were 

 not to be observed directly; but the presence of one pair of openings has been ascertained on sections 

 (PI. VII. Fig. i), as mentioned below. 



This highly rudimentary' condition of the aboral sensory organ is in good accordance with the 

 sessile habit of the animal. For an organism resting mainly in the same position through life there 

 is, of course, not much use of an organ of the nature of a typical Ctenophoran aboral sensory organ, 

 one of the main functions of which (to say the least) is that of being a static organ. 



The inviginations over the genital organs, though decidedly of ectodermal origin, will be men- 

 tioned in connection with the genital organs. 



The "chimneys" have the upper edge bent more or less outwards, collar-like, slightly and 

 irregularly lobed. Along the inner, adapical side of each chimney the narrow tentacle sheath proceeds 

 upwards, opening near its upper edge (PI. I. Fig. 5, PI. III. Fig. 7, PI. VI. Fig. 9). The inner walls of 

 the chimneys are raised into rather prominent longitudinal ridges (PI. III. Fig. 7, PI. VI. Fig. 3). 



The epidermis of the inside of the chimneys is distinctly ciliated. It is composed of three 

 different kinds of cells: clear mucous cells, granular cells and undifferentiated interstitial cells; the latter 

 alone carry the cilia (PI. VIII. Figs, i, 5). The granular cells contain numerous small round grains, 

 which stain ver> strongly with eosine^). (In sections stained with Mann's "Wasserblau-Eosin" these 

 grains are very prominent in the otherwise faint blue tissue). The clear cells are seen in the fresh 

 material (treated with formaline only) to be strongly swollen so as to rise like small cupules over 

 the surface of the epithelium; the often quite slimy appearance of the skin here (and even more so 

 on the basal surface and in the oral cavity) is evidently due to these cells. Seen from the surface 

 the epidermis of the chimneys shows a conspicuously reticulate structure, the meshes being formed by 



M In the sections the epidermis appears generally rather much folded; this being due to the contraction by the 

 transferring of the specimens to alcohol, xylol and paraffine. it has been thought correct to omit the folds in the reproduction 

 of sections (PI. IV— VI). 



-) Comp. Samassa. Zur Histologic der Ctenophoren. .^rcli. f. niikr. Anat. Bd, 40. 1892 p. 163. 



