478 Linncean Society, 



tcct very minute error?, and therefore to speak with certainty as to 

 the accuracy and value of every experiment*. 



LINNiEAN SOCIETY. 



June 5. — Mr. Forster, V.P., in the Chair. 



Read ohservations on the Spongilla fluviatilis. By John Hogg, 

 Esq., M.A., F.L.S. 



Mr. Hogg is disposed to adopt the opinion of Dr. Johnston of 

 Berwick in referring the sponges to the vegetahle kingdom. The 

 lenticular bodies, which occur abundantly in specimens of the river 

 sponge, and which some naturalists, and among others Lamarck, 

 have regarded as the ovaria of the Cristatella vagans, Mr. Hogg in- 

 clines to consider as the sporules or reproductive bodies of the Spon- 

 gilla fluviatilis. These seed-like bodies occur principally in the cells 

 or pores of the sponge. Mr. Hogg has watched the development of 

 these bodies, for having placed some of them in a glass vessel, re- 

 plenished daily with fresh water, six of them soon became attached 

 to the bottom of the vessel, and in about three weeks each of them 

 was found covered with a whitish woolly substance, which he took 

 for the commencement of the sponge ; but unfortunately their further 

 progress was not observed, from the author being obliged to leave 

 home. 



Read also a paper, entitled, on the Number and Structure of the 

 Mammulae employed by Spiders in the process of Spinning. By John 

 Blackwall, Esq., F.L.S. 



The author observes that all the species which have come under 

 his notice are provided with four, six, or eight spinning mammulae, 

 which are somewhat conical or cylindrical, and composed of one or 

 more joints each : they are usually closely grouped in pairs, which 

 may be readily distinguished from each other by their relative posi- 

 tions. The pair situated near the anus is called by the author supe- 

 rior spinners, and that furthest removed from it inferior spinners, 

 and the mammulse placed between these two extremes he terms in- 

 termediate spinners. Exceedingly fine, moveable papillae or spinning 

 tubes, for the most part dilated at the base, occur at the extremity 

 of the mammulse, or are disposed along the inferior surface of their 

 terminal joint, w T hence issues the viscous secretion of which the 

 silken lines produced by spiders are formed. 



Mr. Saunders, F.L.S., presented specimens of Potamogetonplanta- 

 gineus and Medicago denticulata, var. apiculata, gathered in Sussex. 



[* An abstract of Mr. Rigg's paper on the germination of seeds will be 

 found in the Lond. and Edinb. Philosophical Magazine, vol. ix, p. 536 ; see 

 also the same Journal, vol. xii. p. 31, 232. — Edit.] 



