1844.] Linnean Society, 227 



the Society's Transactions, in the first part of which, read before the 

 Society on the 18th of December 1838, those bodies are described 

 as having been observed by him in August 1838, and are compared 

 with the locomotive sporules of the Ectosperma. An abstract of this 

 part of Mr. Hogg's memoir appeared in the ' Proceedings ' of the So- 

 ciety at the beginning of 1839, and was reprinted in the number of 

 the ' Annals of Natural History' for March 1839. Of these several 

 publications Mr. Hogg states that no notice is taken by M. Laurent 

 in his recent work entitled ' Recherches sur I'Hydre et I'Eponge 

 d'Eau douce,' Paris 1844, in which the discovery of the locomotive 

 germs of the freshwater sponge is apparently claimed by the author 

 as his own. 



Mr. Hogg then proceeds to remark on the discrepancies of authors 

 with regard to the existence of cilia on these bodies, and on the 

 spores of the Ectosperma. He accounts for his having overlooked 

 them in the Spongilla, on the supposition that the germs which he 

 observed under a very high power of the compound microscope had 

 reached the period when, as M. Laurent states, " ils perdent leurs 

 cils pour toujours," and notices that it appears, from M. Thuret's 

 recent observations, that the same circumstance occurs in the spores 

 of the Ectosperma. This resorption or disappearance of the cilia 

 after a certain period will readUy account for the denial of their ex- 

 istence by practised microscopical observers. 



The existence of cilia subservient to locomotion is far from deter- 

 mining, in Mr. Hogg's opinion, the question of the animal nature of 

 the bodies to which they belong, although the zoocarpic theory, 

 which he regards as most improbable, appears to be still gaining 

 ground. He believes the motive power of the cilia of the sporules 

 of Spongilla and the Algee, as also of the Sea- Sponges, to be depen- 

 dent on some peculiar organization not connected (as in the loco- 

 motive gemmules of a zoophyte) with any muscular apparatus ; un- 

 less indeed, as he has before suggested, mere endosmosis and exos- 

 mosis should be found sufficient to produce it. 



For these and other reasons which are detailed in his paper, Mr. 

 Hogg still believes both the River and Sea-Sponges to be vegetable 

 productions, and thinks that " until they shall be discovered to pos- 

 sess a stomach or a gastric sac, no zoologist can possibly consider 

 them to belong to the Animal Kingdom." 



