7 6 



THE BRITISH NATURALIST. 



[March 



and Fayod have now more of an historical interest, and do not agree with the most recent 

 observations. The reticular theory of Pfliiger and others still fulfils that condition, at 

 least, for even with the highest magnifying powers protoplasm appears as a fine network, 

 the granules of older observers being largely represented by the corners of the meshes. 

 The lecturer then gave an account of the way in which Professor Biitschli approached the 

 problem from the chemico-physical side, and the observations which led that observer to 

 propound the view that protoplasm was built up of innumerable microscopic vesicles, and 

 had therefore a foam-like structure. The appearance of protoplasm under the microscope 

 supported this theory, and the foam-like substances prepared by Biitschli had not only the 

 appearance of protoplasm, but exhibited many phenomena, such as amoeboid movement, 

 which were considered formerly as attributes of living matter, but were now explained as 

 physical phenomena. The lecturer showed how the application of this vesicular theory of 

 protoplasm helped to explain many puzzling phenomena occurring .in vegetable cells, and 

 accepted it provisionally as the most workable of the theories propounded. In the light of 

 this new theory the older views and newer with regard to heredity were discussed, and 

 the theories of Darwin, Naegeli. Weismann, De Vries, and Wiesner were touched upon, 

 the lecturer adopting the view that the ultimate particles of so highly-organized a sub- 

 stance need not all be similar, as is assumed, for the " plasomes " of Wiesner were 

 probably different in nature or capable of rapid change, and therefore of differentiation. 



A vote of thanks to Professor Weiss, proposed by Mr. W. Blackburn, F.R.M.S., seeonded 

 by Mr. M. L. Sykes, F.R.M.S., and carried with acclamation, concluded a most succtss- 

 ful'and enjoyable meeting. 



MICROSCOPY. 



Collecting Diatoms. — Bright brown patches of diatoms, frequently 

 seen coating the surface of mud, may be collected in the following 

 manner. Half fill a bottle with water, touch one of the brown patches 

 with the tip of the finger, and the diatoms will adhere ; place the tip 

 ■of the finger to which the diatoms are adhering over the mouth of the 

 bottle, shake it, and the diatoms will be washed off. By frequently 

 repeating this process, the water will become quite brown, and by the 

 time the collector reaches home, the diatoms will have settled to the 

 bottom; the water may now be decanted, and the diatoms cleaned. The 

 collector is recommended to examine every promising patch of brown 

 under a lens, for very fine pure gatherings of quite different species may 

 not unfrequently be gathered within a few feet of each other. 



Mounting Fresh Water Alg,e. — -The following is the method of 

 mounting fresh water algae in glycerine or glycerine -gelatin, adopted by 

 Dr. L. Klein. Glycerine he uses for small objects, adopting for this 

 purpose the technique proposed by Migula. A drop of one per cent, of 

 osmic acid is run under the cover glass, followed by the glycerine in ten 

 to twenty minutes afterwards. In order not to blacken the oil drops, 

 &c, the osmic acid is added in as small quantities as possible ; the best 

 method being to blow it under the cover glass through a capillary tube. 



