Mr. H. J, Carter on the Ultimate Structure of Spongilla„ 31 



vent is seen to project itself as gradually as it became contracted, 

 the investing membrane to resume its original position, and the 

 apertures in both to open and admit and emit their currents 

 respectively as before ; but now, the latter brings away the re- 

 fuse of the carmine which has been and is still being thrown off 

 into the efferent canals. In fact, the Sjiongilla, having been fed 

 to satiety, appears thus to shut itself up for a time for the pur- 

 pose of digestion, and then to open to throw off the refuse. 



Again, it sometimes happens that one of the large branches of 

 the efferent system bursts and gives rise to an efferent current 

 before the tubular vent resumes its original dimensions and 

 opens its aperture, by which two efferent currents are subse- 

 quently established, for the abnormal one does not close when 

 the normal one becomes opened. Hence we have a further in- 

 dication of pressure on the contents of this system, which will 

 hardly derive explanation from anything but a force exerted by 

 the contracting vesicles in the way mentioned ; the conditions of 

 the fluid in the afferent and efferent canals hardly holding out a 

 sufficient difference in composition or density to account for this 

 by endosmosis. 



Thus we find Spongilla (for I have ascertained that the same 

 structure exists in the large masses as in the small ones) com- 

 posed of a number of stomachal sacs imbedded in a gelatinous 

 substance permeated with spicules for its support, and an ap- 

 paratus for bringing them food, as well as one for conveying 

 away the refuse, while the nutriment which is abstracted by the 

 process of digestion common to Rhizopodous cells {e. g. Amoeba) 

 no doubt passes through the intercellular gelatinous substance 

 into the general development of the mass ; and if right in com- 

 paring the ampullaceous sacs to the stomachal cavities of the 

 simplest Polypes, are we not further justified in drawing a resem- 

 blance also between the ciliated sponge-cells and those which 

 line the stomach of Cordylophora^, of Otostomaf, and many of 

 Ehrenberg's Allotreta together with those in the stomach of 

 the Rotatoria and PlanaricE J, which are evidently biliary organs, 

 also having cilia floating in the cavity which receives the food ? 



Lastly, it is perfectly evident that each monociliated sponge- 

 cell possesses a large granule (PI. I. fig. 10 c), which is of a 

 greenish colour, and that the assemblage of these cells in the 

 interior of the ampullaceous sac produces the assemblage of 

 granules which are seen in it; also that these granules, when 

 the ampullaceous sac becomes individualized and assumes an 

 actinophorous form, represent the "granules'' which I have de- 

 scribed as a part of the internal contents of the Rhizopoda (fig. 9). 



* See Prof. Allman in Phil. Trans. 1853, p. 3/0. 



t Annals, vol. xvii. p. 117- + Idem, vol. xviii. pi. 7. fig. 92. 



