502 Extracts from the Minute-Book of the Linnean Society. 



placing them : C. alopecurus, Lap. ; C. juncoides, Presl ; C. costata, 

 Presl ; C. furcata. Lap. ; C. manostachys, Spr. ; C. fusca. All. ; C. 

 nesliaca, Suter ; C. Bastardiana, DeC. ; and C. hadia, Pers. 



Dec. 17- Read "Additional Remaiks on Spongilla fluviatilis" by John 

 Hogg, Esq., M.A., F.R.S., F.L.S., F.C.P.S. &c. &c. 



In this paper Mr. Hogg commences by claiming a priority to M. 

 Laurent in discovering the locomotive germ-like bodies of Spon- 

 gilla, in ascertaining that they are a second sort of reproductive 

 bodies of that substance, and in comparing them with the sponta- 

 neously moving sporules of Ectosperma clavata of Unger. In proof 

 of this priority he refers to his memoir, published in 1840, in the 

 third part of the eighteenth volume of the Society's Transactions, in 

 the first portion 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, are proved by direct experiment to be 

 capable of reproducing the Spong'illa, and are compared with the 

 locomotive sporules oi Ectosperma. An abstract of this portion of Mr. 

 Hogg's memoir appeared in the ' Proceedings ' of the Society 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'fiponge 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 

 sporules 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 sporules 



