Microscopical Society. 2811 



the store laid up for the zoophagous Odynerus larvae, nor was there any trace of subse- 

 quent occupation by an Osmia. In another instance he found, in an excavated briar, 

 the lower part tenanted by three larvae of Cemonus, and the upper portion by several 

 larvae of Hylaeus : in this case, the time for the appearance of the perfect Cemoni 

 being prior to that of the Hylaei, the latter were destroyed by the former while making 

 their exit. The memoir concluded by saying that the specimens illustrative thereof 

 were now presented to the Society. 



Referring to Mr. Saunders's Memoir, Mr. Westwood observed that he had thought 

 the Hylffii were parasitic ; and Mr. Smith said that he did not believe they were pa- 

 rasitic, for he had seen individuals excavating bramble-sticks for their cells. 



Copies of the President's Address at the Anniversary Meeting, and of Part i. vol. i. 

 of the new series of the Society's Transactions, were laid on the table. — /. W. D. 



Proceedings of the Microscopical Society of London. 



April 17, 1850. — Dr. Aethuk Faree, President, in the chair. 



Capt. R. H. Manners, R.N., J. B. Mummery, Esq., H. Cantis, Esq., Capt. Trotter, 

 C. F. White, Esq., F. H. Wenham, Esq., and R. Meslayer, Esq., were balloted for 

 and duly elected members of the Society. 



A translation of a letter from M. Nachet, respecting the construction of his prism, 

 was read. 



A paper, by F. H. Wenham, Esq., " On a New Method of Illumination," was 

 read. After some preliminary observations, in which allusion was made to the want 

 of sufficient aperture in Nachet's prism, and also to some supposed defects in its mode 

 of action, the author proceeded to describe a construction by which those defects 

 might, in his opinion, be remedied. It consists chiefly in the employment of two of 

 Nachet's prisms in juxtaposition with a dark well between them, by which means he 

 expects to be able to throw an oblique pencil of light in two opposite directions across 

 an object, and thus not only produce a greater amount of light, but also correct many 

 of the false appearances produced by the former mode of illumination. This arrange- 

 ment, however, he had not as yet had an opportunity of carrying into effect, although 

 he did not doubt of its success. 



He next proceeded to describe another mode of illumination, consisting of a 

 parabolic reflector of one-tenth of an inch focus, with a polished silver surface, having 

 the apex so far cut away as to bring the focal point to such a distance above the top 

 of the apparatus, as may be equal to the thickest glass commonly used for mounting 

 objects ; a disk of thin glass is placed at the base of the parabola, in the centre of 

 which is cemented a dark well, with a flange rather larger than its diameter, being 

 equal to the aperture at the top of the reflector, for the purpose of preventing the 

 direct rays from passing through the apparatus. There are various necessary adjust- 

 ments, and a revolving diaphragm having two apertures may also be applied, by 

 means of which two pencils of light in opposite directions may be obtained, if 

 required. The apparatus was exhibited, in action, after the meeting, and appeared 

 fully to realize the views of the inventor. — /. W. 



