PEOOEEDINGS OF THE SOCIETY. 359 



the stage may be kept fixed wMle the light is revolving round it in any 

 direction horizontal or vertical, always, however, remaining npon the 

 object " (post). 



Mr. J. Mayall, jiui.» described the " Nelson Model Microscope," exhibited 

 by Mr. Baker (supra, p. 292). 



Mr. G. Masses gave a resume of his paper " On the Differentiation of 

 Tissues in Fungi " (supra, p. 205). 



Mr. A. W. Bennett spoke of the interest attaching to Mr. Massee's 

 paper, inasmuch as so much attention had not been paid to the differentiation 

 of tissues in Fungi as in the higher Algfe, where we often get distinct tissues 

 adapted for assimilation, for conduction, and for strengthening. He did 

 not think, however, that this affected the primary classification of the 

 vegetable kingdom into Cellular and Vascular plants, since it is doubtful 

 whether any true vessels exist in Thallophytes. The cystidia of the 

 Basidiomycetes he did not regard as having any sexual fimction whatever. 

 They frequently contain large crystals of calcium oxalate. 



Professor Stewart said that, although the interest of any structure is 

 naturally greatly enhanced when we are able to recognize the function it 

 performs, we must bear in mind the fact that it may have no duty to accom- 

 plish, but be only the result of certain forces acting on the organism, or be 

 but the remains of something of use in past times. Might not the cystidia 

 be produced by the more abundant ascent of fluids through the laticiferous 

 tubes at certain periods, causing an expansion of their free, unsupported 

 extremities ; the fluid contents finally escaping either by exuding through 

 the thin walls of the cystidia or producing their rupture ? 



Drs. H. J. Johnston-Lavis and G-. C. J. Vosmaer's paper •' On cutting 

 sections of Sponges, and other similar structures with soft and hard 

 tissues," was read by Professor Bell (supra, p. 200). 



Mr. B. B. Woodward gave some further explanations as to the specimens 

 exhibited in illustration of the paper, which were of exceptionally large 

 size. 



Professor Stewart said that large and thin sections of sponges were often 

 of great use by enabling one to determine the natural relationship of distant 

 parts to one another, so that the method described would probably be of 

 chief use in making such sections of the harder sponges. He thought, how- 

 ever, that the simpler freezing method would suffice in most cases. For 

 investigations into the more minute structure, he had obtained the best results 

 by hardening in osmic acid and alcohol, freezing, and cutting with a 

 microtome, and mounting in a solution of acetate of potash, without further 

 staining, or staining with carmine or logwood, and mounting in Canada 

 balsam. 



Professor Bell considered that large sections would be found useful in 

 the systematic of sponges, as an assistance to classification. 



M. L. Chabry's capillary tube-slide and perforator of cell-elements 

 was similarly exhibited and described (supra, p. 319). 



Mr. F. Kitton's note on Styrax and Canada Balsam was read as 

 follows : — 



" For the last few months I have been using a mixture (equal parts) of 



