1900] MICROSCOPICAL JOURNAL. 197 



should be mounted in this fluid in hollow ground glass 

 slips. The objects have all the appearance of living ani- 

 mals, the colors, internal structure, and outward form be- 

 ing beautifully preserved in situ. 



Moulds. — In observations on the microscopic life of 

 Arctic regions, Dr. Levin states that air from numerous 

 localities showed only a few moulds. In water from the 

 sea-surface bacteria were always found, but in very small 

 numbers — perhaps one thousand to a quart; while water 

 from glaciers, snow streams, ice and melted snow, also 

 gave evidences of bacteria in small numbers. In water 

 from the deep sea these organisms were more abundant 

 than on the surface. With the exception of a single spe- 

 cies of bacterium found in one bear and two seals, the in- 

 testi lal contents of the white bear, seal, shark, eider duck, 

 and other Arctic vertebrates were absolutely sterile, but 

 bact(!ria were almost invariably present in the lower ma- 

 rine animals. These observations on germ-free intestines 

 are c f special importance and interest, as tl^ey confirm the 

 idea of Pasteur and a few others that bacteria are not es- 

 sential to digestion. 



Rr.ALGAR. — In his address to the Quekett Society, Dr. 

 Tatham alluded to the difficulties attending the use of 

 realgar as a mounting medium. Its high refractive index 

 mak<'S it most useful, but its disadvantages are many and 

 serious. The fusion of the material which is necessary 

 for the mounting process requires the application of great 

 'heat. This liberates intensely poisonous fumes, and fre- 

 quently so distorts the valves of the diatoms that they 

 are seldom found to lie flat on the cooling of the slide. 

 The color of the finished mount is a deep yellow, and this 

 seriously detracts from the valu^ of the mount for criti- 

 cal examination. This last defect may be partially rec- 

 tified by the use of suitably colored screens, of which a 

 polislied plate of bright blue glass has been found to be 

 best adapted to aiding in the resolution of difficult tests. 



