492 



somewhat at the loss of resolution and of course of intensity of 

 light. 



The fifth exhibit was lighted by a Nernst electric and Nelson 

 formula double condenser, and showed living bacteria with dark- 

 ground illumination. 



The sixth stand had the same optical parts as the others, ex- 

 cept that the condenser had an oil-immersion, and the specimen 

 was Amphipleura pettucida in realgar. The illuminant was 

 Barnard's form of mercury-vapour lamp. A micro-spectro- 

 scope was also provided to demonstrate the effect of the realgar 

 in nearly cutting out the violet and blue lines of the mercury 

 spectrum. 



A very hearty vote of thanks was returned to Mr. Lees Curties 

 for his interesting exhibit. 



A paper by Messrs. E. Heron-Allen, F.L.S., F.R.M.S., and 

 Arthur Earland on "A New Species of Technitella from the 

 North Sea, with Some Observations upon Selective Power as 

 exercised by Certain Species of Arenaceous Foraminifera," was 

 read by Mr. Earland. The paper made no attempt to explain 

 either the processes by which the tests of Arenaceous Foraminifera 

 are constructed, or the idiosyncrasies displayed by many of the 

 genera and species in the choice of materials. But the discovery 

 of a species in the construction of whose test the utmost limit 

 hitherto observed is reached, both as regards construction and 

 selection, seemed to the authors a fitting opportunity to assemble 

 and record some of the facts that present themselves to the 

 student whilst observing these more or less highly specialised 

 organisms. 



Mr. E. F. Law gave a lecture, illustrated with photomicrographs 

 in the lantern, on " The Relation between the Microscopic 

 Structure and Properties of Alloys." He said that the only 

 additional piece of apparatus required for the study of opaque 

 objects was an illuminator such as the Sorby-Beck for low powers, 

 and for higher powers a right-angled prism behind the objective 

 or a transparent mirror, such as a cover-gla^s. In such cases 

 the light was reflected through the objective on to the specimen 

 and back again to the eyepiece. Dealing with the preparation 

 of metal sections for microscopical examination, the usual method 

 was to obtain a section from a selected sample by sawing or 

 breaking up the mass. The piece was then filed to get a level 



