PROCEEDINGS OF THE SOCIETY. 189 



Mr. Michael said he had been afforded an opportunity of examining 

 this lens, and it struck him that the large size of the field would be 

 found to be of very great advantage. This, together with its long 

 focus and excellent definition, made the lens a very useful addition to 

 the existing means of casual investigation. 



Mr. Crisp exhibited some of Dr. Zenger's double-sided slides for 

 mounting objects so that both sides could be examined if required. 

 The slides had an aperture pierced through the centre so that two 

 thin glass covers could be put on with the object between them. 

 (Vol. v., 1885, p. 908). 



Messrs. Coxeter and Nehmer exhibited their new silico-carbon 

 battery and incandescence lamp for the Microscope. 



Mr. C. Beck exhibited a form of the " Star " Microscope, which had 

 been specially fitted to suit the reqiiirements of petrological investi- 

 gation ; also a battery and incandescence lamp for the Microscope. 



Mr. Crisp exhibited Prof. Martius' stroboscopic apparatus for 

 determining by the vibration of a lever on the armature of an electro- 

 magnet the rate of ciliary vibration in cells, Rotifers, Infusoria, &c. 

 The lever carried a small diaphragm of paper at the end, by which 

 means the rays from the illuminator were periodically cut off and 

 admitted to the Microscope. 



Mr. Deby's note on the discovery of Amphipleura Undheimerii in 

 Spain, was read. (Supra, p. 172.) 



Mr. A. W. Bennett gave a resume of his paper ' On the Fresh- 

 water Alga3 of the English Lake District,' illustrated by coloured 

 diagrams and drawings on the black-board (supra, p. 1). 



The President said that the paper afforded an excellent illustration 

 of the kind of work which was within the reach of all present, and 

 which could be carried out with the instruments which they possessed, 

 and it showed how it was possible to ultilize a holiday by doing good 

 work and at the same time adding to the pleasure derivable from it. 

 It had often seemed to him that work of this kind was apt to become 

 periodic ; they did certain work, and then there seemed to be years of 

 pause in which very little more was done in the same direction, and 

 in the case of the Desmids there was still a large field open to those 

 who were willing to devote themselves to the study. The literature 

 of the subject was not so great as might have been expected, and 

 it was quite within the power of any one who would try, to add a 

 great deal to their knowledge of these organisms. He felt sure that 

 the Fellows of the Society were much obliged to Mr. Bennett, not only 

 for his paper, but also for the very concise way in which he had 

 presented to them the results which it embodied. 



