52 



screen of sulphate of copper and bichromate of potash. One 

 of the best screens was of a green glass of such a tint as to cut 

 out the red in a bright spectrum. Those who did not possess 

 a spectroscope could get a good spectrum by means of any coarse 

 diatom by using a narrow pencil, and viewing the spectra at the 

 back of the objective wlien the eye-piece was removed. 



Mr. Ingpen said that a splendid spectrum could be obtained 

 in this way with a Cherryfield rhomboides. 



The President said that when diatoms were examined on a 

 dark ground colours were often seen, red indicating a coarse and 

 blue a fine structure. In the early days of his microscopical 

 work he had noticed a blue line on the girdle of a Pinnularia 

 major, and he at once recognized this as indicating the presence 

 of fine structure. It was not long before he had resolved it into 

 60,000 stria? per inch. It was an interesting question whether 

 this consisted of rows of minutely perforated structure, if so it 

 must wait for an objective of the future to resolve it, as it was 

 beyond the reach of the best modern objectives. It would be 

 more difficult than the longitudinal stria? on the A, pellucida, as 

 there were no edges and raphae for the manufacture of false 

 ghosts. 



Mr. Ingpen said that the medium piperine was irrational. 

 There were some high refractive media he could recommend, 

 among which he might specially mention that composed of one 

 part of bromide of antimony, one part of bromide of arsenic, and 

 one part of piperine. This mixture was rather yellow, but it 

 melted easily at a low temperature. 



The Secretary announced that nominations for members to 

 serve on the Committee must be made at their next meet- 

 ing- 

 Announcements of meetings, etc., for the ensuing month 

 were then made, and the meeting terminated with the usual 

 conversazione, the following objects being exhibited : — 

 Stephanoceros Eichhornii ... ... ... Mr. W. Burton. 



Tcwdigrada (sp. ?) Mr. C. Eousselet. 



