PROCEEDINGS OF THE SOCIETY. 351 



be a demonstration and discussion on the Aperture Theory of the 

 Microscope. 



Mr. Beck said he should like to ask any Fellows of the Society who 

 were possessors of the Abbe diffraction plate if they would kindly lend 

 these for use in illustration of the subject to be brought before their 

 next Meeting. Mr. J. W. Gordon would endeavour to show that the 

 effects, as described by Professor Abbe, and relied upon by him to prove 

 his diffraction theory, were produced, not by the object on the stage, but 

 by the diaphragm over the object-glass ; and, to make the subject more 

 clear, they were anxious to have as many sets as possible of the diffrac- 

 tion apparatus for exhibition on that occasion. They did not want a 

 very large number, but he thought that five or six sets would be required 

 in addition to those which they already had. 



The Chairman said they had that evening a large number of objects 

 exhibited to illustrate various forms of aquatic life, which he was sure 

 would be examined with much interest. He felt that as a Society they 

 were very much indebted to those gentlemen who had kindly assisted 

 in bringing so good a collection together 



The meeting was then resolved into a Conversazione, at which the 

 following objects were exhibited: — 



Mr. Ed. Bartlett:— Vor ticella. 



Mr. Alfred W. Dennis : — Plumatella repens, issuing from statoblast. 



Mr. A. Downs : — Fredericella sultana. 



Mr. A. Earland : — Awirsea brevispina. 



Mr. T. D. Ersser : — Hydra vulgaris. 



Mr. A. J. French : — Stentor polymorph's. 



Mr. Alfred E. Hilton '. — Cristatella mucedo. 



Mr. E. E. Hill -—Plumatella. 



Mr. E. Hinton : — Chara fragilis. 



Mr. J. T. Holder : — Photomicrographs from life, Larva of Caddis-Fly. 



Mr. G. E. Mainland: — Corethra plumicornis, Larva, Pupa and Imago. 



Mr. K. I. Marks : — Awirsea aculeata, A. coclilearis, Asplanchna prio- 

 donfa, Bracliionus angularis, Polyarthra platyptera. 



Mr. C. Muiron : — Anursea brevispina, Asplanchna priodonta, Bracliionus 

 pala, Triarthra longiseta. 



Mr. Julius Rheinberg : — Cristatella mucedo, statoblast. 



Mr. G. H. J. Rogers : — Melicerta ringens, Volvox globator. 



Mr. C. F. Rousselet : — Cristatella mucedo, Stephanoceros eichhorni 

 with winter eggs, and various Rotifera. 



