182 THE AMERICAN MONTHLY [June 



Through the orifice introduce the cultivating media con- 

 taining a small quantity of a culture of, say, Nitzscliia 

 longissima, and expose it to the light. In the course of 

 time the interior of the cover-glass will be covered with 

 a beautiful growth of the frustules of the diatoms. This 

 cell must, of course, be stood upright on its side. Cells 

 may also be prepared by making the orifice in the cover- 

 glass. 



Cleaning. — To clean cover-glasses and slides, immerse 

 for one hour in a mixture made by adding to a saturated 

 aqueous solution of potassium bichromate about one- 

 eighth of its bulk of strong sulphuric acid. This will 

 also be found useful for cleaning glasses that are intend- 

 ed for use as colored screens. 



Fixing. — Herr K. Koninski suggests a new gelatin- 

 formalin method for fixing paraffin sections to the slide. 

 The plate is first covered with a film of gelatin by the 

 usual method, and, when this has set, ribands of sections 

 are arranged on it. The plate is then gently warmed un- 

 til the gelatin has liquefied. Remove the superfluous 

 gelatin with bibulous paper and allow the preparation to 

 set. To render the gelatin firm and insoluble, the plates 

 are immersed in pure formalin for ten minutes. Thus 

 prepared, the mounts are sufficiently hard to resist the 

 action of boiling water. 



Cement. — The following will be found to be a useful 

 cement for making live-cells and zoophyte troughs, and 

 for cementing the glass of aquaria. Dissolve gum elastic 

 and thoroughly rub in with it a sufficiency of white lead 

 and linseed oil varnish to form a paste. 



Fluid Mounts. — The last number of the Journal of the 

 Quekett Microscopical Society contains a resume by F. 

 Rousslet, on "Micro-Cements for Fluid Mounts." The 

 author has obtained his best results by first giving a coat 

 of pure damar in benzole, then a coat of a mixture of 

 damar and gold-size, then three or four thin coats of pure 



