ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 173 



would have trouble to distinguish it from the commoner European 

 species. I do not suspect for one minute that Herr Mollcr himself 

 would knowingly offer for sale test slides of the coarser diatom under 

 the name of A. pellucida ; but others might be found not quite so 

 scrupulous. 



Special slides, it is well known, are often kept of A. pellucida, of 

 P. angulatum, of F. saxonica, of Surirella gemma, and others, for the 

 best exhibition of high-power objectives ; and these pet ' coarse ' slides 

 are in general not willingly parted with by their fortunate owners. 

 My advice is, ' Make sure in future that the A. pellucida you resolve 

 with ease is not one of Don Truan y Luard's A. LindheimeriiJ 



This last diatom is figured in Grunow, 1862, pi, XI. fig. 11, and 

 was distributed by Prof. H. L. Smith, in his ' Species Typicje,' No. 17. 

 A careful examination of either of these will prevent any confounding 

 of the two species." 



Bevel-edge Slips.* — The Palmer Slide Company, of Geneva, N.Y., 

 have recently introduced slips with bevel edges. These are said to 

 be "certainly very attractive in appearance, and well adapted for 

 ornamental preparations." Some are plain glass, very colourless and 

 free from defects, others are flashed with a colour on the under sur- 

 face, which modifies the light, or adapts them very well for opaque 

 mounting. Careless handling may, however, result in chipped corners. 



Mr. G. S. Woolman, in further recommendation of the slips, says, 

 " Aside from the great beauty of the finished object, making them 

 the most elegant slide yet introduced, their bevel edge allows them 

 to slide smoothly under spring clips on the stage of the Microscope. 

 They are made of Chance's crystal plate and Chance's flat crown, and 

 with ground edges, or ground and polished edges." 



Adhesiveness of Cements.* — Prof. A. B. Aubert has made com- 

 parative tests of various cements, using metallic cells, and leaving the 

 cement to harden for 103 days. 



Starting with Miller's cement = 1000, the following table 

 represents the comparative adhesiveness of the cements tested : — 



Miller's caoutchouc cement 1000 



Bell's cement (shellac in alcohol ?) 735 



Canada balsam 664 



Lovett's cement (this Journal, III. 1883, p. 786) 626 



American styrax 575 



King's cement 532 



Gold size 395 



Dissolved marine glue 304 



Zinc white cement 241 



The gold size was not sufficiently hardened or it would have been 

 higher in place. 



Strong Cements I . — The following formulae are given anonymously 

 for cementing brass cells to glass slides : — 



,\ * Amer. Mon. Micr. Journ., xi. (1885) p. 239. f Ibid., vi. (1885) pp. 227-9. 

 J Micr. Bulletin (Queen's), ii. (1885) p. 45. 



