210 THE AMERICAN MONTHLY [July, 



DIATOMS. 



Cultivation of Diatoms. — Dr. L. Macchiati, in a communica- 

 tion to the Journal de Micrographie, points out that diatoms are 

 easily cultivated in the nutritive solution used in vegetabl'^ 

 l)hysiology, provided that a few drops of silicate of potash be 

 added to the medium. Or, the very water which the diatoms 

 inhabit may be used. This when filtered, and wi'h the addi- 

 tion of a few drops of strong silicate of potash solution, forms 

 an excellent fluid. The medium placed in a watch-glass is 

 then inoculated with a loopful of the water inhabited by the 

 diatoms, and the two fluids having been thoroughly mixrsd 

 together by stirring, a loopful of the mixture is placed on the 

 surface of a cover-glass; the exact thickness is previously ascer- 

 tained. To the margin of a cavity of a hollow-ground slide is 

 then applied pome vaseline, and this is carefully pi iced over 

 the cover-glass. The slide, now containing a hanging-drop 

 cultivation, is turned over. In such a drop the diatoms are in 

 an almost natural state, and their development and mode of 

 life may be watched under a power as high as 1-18, though the 

 lens commonly employed by the author is a dry apochromatic 

 with focal distance of 4 mm. and N. A. 0.95. In combination 

 with eye-pieces 6, 12, and 18, magnifications of 372, 750, and 1, 

 125 were obtained. The best part for observing the diatoms is 

 the edge of the drop, and this should be first centered under a 

 low power. — English Mechanic. 



MICROSCOPICAL SOCIETIES, 



Calcutta, India. 



The year lSd2. — Number of Members, 81, an increase of 3. 

 Receipts $200; Expenses $125; Balance on hand, December 31, 

 $75. The Fifth Annual Report [7 pp.) was issued in January, 

 1893. Ten papers were read during 1892, as follows : 



By J. Vv^ood-Mason, (1) on the Stridulating organs in one of 

 the Myriapods, (2) an elementary account of the Protozoa. 



B}^ W. J. Simmons, (1) on diatoms from Hungary, (2) the eye 

 oi Eristalis tenax, (S) on Hyaline Spherules found in cerrace- 

 dust. 



