with some Remarks on the Nature of the Spongiee Marinee. 381 



Sponges. And I much suspect, that were these bodies belonging to several 

 more kinds of Spongla magnified 400 or 500 times, what have hitherto been 

 taken for cilia* will prove to be either papillœ similar to those in the sporules 

 of the Spongilla JluviatiUs, and that the supposed vibrations in the water are 

 in reality only endosmose and exosmose currents through the membranes of 

 these bodies and their papillae ; or else, if when slightly magnified they appear 

 like the true cilia of animals, they will under a higher power of the micro- 

 scope be ascertained to be small tubules, as well through which, as through 

 the membranes of these germlike bodies, the same reciprocal action of fluids 

 takes place, and thereby most probably effects tlieir remarkably similar move- 

 ments. 



Moreover, since I have already attempted to describe the locomotive germ- 

 like bodies of the River Sponge, and have alluded to those of the Sea Sponge, 

 the sporules of the club-shaped Ectosperma amongst plants, and the sponta- 

 neous movements of the Globe Volvox among the Infusorians, it only remains 

 to consider, for the sake of comparison, the moving germs or gemmules of 

 some animal wliich strictly belongs to the Zoophytes. For this object, I will 

 select the locomotive gemmules of the Jlci/onium gelat'mosum (Linn.)t, as 

 they have been so recently discovered by Dr. A. Farre, and by whose kind- 



* Since Dr. Grant is evidently in error as to the tentacula of the Sertulariœ being ciliated, (see 

 Edinb. Pliil. Journ. vol. xiii. p. 101,) I cannot but think that he is under the like mistake respecting 

 cilia being also present upon the locomotive sporules of the Sea Sponges. Both Dr. Johnston in hii 

 Brit. Zooph., p. 43, and Mr. Lister in his memoir in the Phil. Trans, for 1834, p. 377, have subse- 

 quently ascertained that the Sertulariœ have no cilia. The family Sertidariadie belonging to my 

 Unosculous subclass of Zoophytes, I propose to arrange in an order called Noditentacvla, from their 

 tentacles being furnished with nodi, small knots or projections. Such minute processes, without the 

 aid of a very good microscope, and in a clear, strong, and equalized light, may very easily deceive the 

 eye of the observer. And I may remark, that my proposed order corresponds with a part of Dr. 

 A. Farre's Polypi Nudibrachiati ; but here it will be evident that this term is inapplicable to those 

 Zoophytes whose tentacula or brachia are rough with small knots or nodules, and are furnished with 

 irregular hairlike projections according to the observations of M. Trembley on the Hydrie, and of 

 Mr. Lister on the Sertulariœ. 



t It is the Hulodactylus diaphauus of Farre ; the Alcyonidium gelatinosmn of Johnston (Brit. Zooph.) ; 

 the Ulva diaphana and Alcyonidium diaphanum of many botanists. It is singular that it should have 

 been so lately classed among plants, for its polypes were long ago mentioned in Solander and Ellis's 

 work on Zoophytes. See also the note of Mr. Gray in his paper on Sponges, at p. 50 of the Zoolo- 

 gical Journal, vol. i. 



