108 PROCEEDINGS OF SOCIETIES. 



at the meeting, make admirable microscopic objects, easily pre- 

 pared, and everlasting. All known sponges are marine, except 

 the genus of which the living species then produced is a member. 

 It occurs near St. Martin's Hill, in the vicinity of the Eeed 

 Pond, and in several other places down the Stour river, and may 

 be found on posts, sticks, and weeds, in pools and streams, and 

 commonly appears between wind and water. 



October 12th. — Mr. Sibert Saunders exhibited lively specimens 

 of Coryne pusilla, Sertularia fllcula, Alcyonidium parasiticuni, and 

 YalJceria cuscuta. Col. Horsley and Mr. Harvey continued tlieir 

 illustrations of the new method of microscopic illumination, and 

 with satisfactory results. Mr. Gulliver gave an Address " On the 

 Objects and Management of Provincial Museums," which is 

 reported in the ' Kentish Gazette,' Oct. 17, ' Land and Water,' 

 Oct. 28, ' Nature,' &c. 



October 2Qth. — The evening was chiefly occupied by Col. Cox's 

 interesting lecture " On Beach Pebbles," including their micro- 

 scopic structure. 



November 9fJi. — The evening was fully occupied by the most 

 instructive lecture of the Eeverend President, Dr. Mitchiuson, 

 " On Hypersthene and Amygdaloid," illustrated by numerous 

 specimens collected by him in Skye, and by drawings in water- 

 colours by R. G. Gordon, Esq., Assistant-Master of the King's 

 School. 



November 2Brd. — Col. Horsley continued his experiments on 

 the effects of different methods of microscopic illumination, es- 

 pecially as regards the appearance of the lines or markings on the 

 valves of JPleurosigma anffuJatum, P. qnadratum, and P. hij^pocam- 

 pus, using a quarter-inch object-glass and transmitted light. The 

 results were so remarkable as to throw doubts on the taxonomic 

 value of the current descriptions of the direction of those mark- 

 ings. Thus, in the former two species, the markings appeared 

 either transverse or oblique, according to the direction of the 

 light, so that they could be made to present a transverse course 

 in one light, and a diagonal course in another light, effects that 

 were produced to admiration as often as desired. But in 

 P. liippocavipus no such effect could be seen ; for in this species 

 the lines always appeared transverse and longitudinal, Iiowever 

 the light might be managed. 



