30 Mr. H. J. Carter on the Ultimate Structure of Spongilla. 



on either side of the ciliuni, by which the particles may be seen 

 to be thrown almost point-blank on its surface, and at the same 

 time caught up (by apparently adhering to it, or by a process 

 thrown out by it as in Actinophrys Sol {b) ) and rapidly passed 

 into the interior. Hence we may easily conceive the united effort 

 of all the ciliated sponge-cells in the ampullaceous sac being 

 sufficient to produce a considerable current into its interior, and 

 thus to catch the particles which are passing through the afferent 

 canals. 



The other question, viz. that of the afferent and efferent cur- 

 rents, is not so easily solved, but still the monociliated sponge- 

 cell supplies data for at least speculation on that point. I have 

 already shown, in my notes on the organization of the Infusoria, 

 that the vesicula or contracting vesicle is an excretory organ, 

 and that it discharges itself from the surface in many Infusoria, 

 especially in the naked Rhizopoda, to which the sponge-cell is 

 most intimately allied ; and it so happens, that not only do these 

 monociliated sponge-cells present the contracting vesicle in 

 great activity, but also in variable plurality, so that with those 

 of the other sponge-cells lining the cavity of the ampullaceous 

 sac, a continual and rapid discharge of water must be kept up ; 

 which, when we remember that it is the character of this organ 

 to discharge itself from the surface, and find that when the am- 

 pullaceous sac leaves the parenchyma it becomes nothing more 

 than a large sponge- cell, gives us, I think, pretty good reason to 

 infer that these organs discharge their watery contents into the 

 efferent system of canals ; and, when v;e consider the powerful 

 organ which the contracting vesicles of all the ampullaceous cells 

 together must form for effecting this function, it does not seem 

 unreasonable, in connexion with the following facts, to conclude 

 that the currents, both afferent and efferent, of the sponge may 

 be produced in this waj*. 



It might be supposed, from what has been stated respecting 

 the course of the particles of carmine through Spongilla, that 

 the afferent and efferent currents never cease as long as it is 

 alive ; but such is not the case under some circumstances, for 

 although no difference is appreciable when only a small quan- 

 tity of carmine has been taken in, yet when there is an abun- 

 dance in the water, and the ampullaceous sacs become apparently 

 filled with it, not only do these sacs one after another seem to 

 close their apertures and refuse admittance to any more, but the 

 whole investing membrane becomes drawn towards the paren- 

 chyma, its apertures all become closed, and the tubular vent of 

 the efferent system retracted, and its aperture also closed, so 

 that there is a total cessation of all active motion m the Spon- 

 gilla ; and this may continue for more than an hour, when the 



