470 Journal of Applied Microscopy. 



MOUNTING DIATOMS. 



The silicious shells of diatoms are among the most beautiful objects which 

 could be examined with the microscope. To obtain perfectly clean mounts 

 requires considerable time and patience, but when the material is once cleaned, 

 preparations may be made at any time with very little trouble. Diatom enthu- 

 siasts have devised numerous methods for cleaning diatoms, and separating the 

 various forms from each other, but we shall give here only a few simple, practical 

 methods. 



Many scouring soaps and silver polishes contain large quantities of diatoms, 

 and the diatomaceous earths are particularly rich. Break up a small lump of 

 such material and boil it in hydrochloric acid. A test-tube is very convenient 

 for this process. Let the diatoms settle, pour off the acid, and then wash in 

 water. As soon as the diatoms settle, the water should be poured off. The 

 washing must be continued until no trace of acid remains. After the washing is 

 complete, pour on absolute alcohol, and after ten or fifteen minutes pour off the 

 alcohol, and add just enough xylol or bergamot oil to cover the sediment. The 

 material, of course, will keep indefinitely in this condition, and may be mounted 

 in balsam at any time. 



The method just given refers to fossil diatoms. A convenient method for 

 mounting the frustules of living forms is given in the March number of this 

 journal. 



If it is desired to bring out the nucleus, centrosomes, and chromosomes, 



Flemming's fluid, followed by the safranin-gentian violet-orange combination, may 



be recommended. Haidenhain's iron-alum-haematoxylin is very good for the 



centrosome. 



MOUNTING BACTERIA. 



The methods of modern bacteriological technique are so numerous and so 

 specialized that we must refer to laboratory manuals for instruction in this 

 subject. The method given here will merely enable the student to recognize the 

 larger bacteria. 



Foul water at the outlets of sewers and such places will usually afford an 

 abundance of coccus, bacillus, spirillum, and beggiatoa forms. Place a drop of 

 the water on a slide, heat it gently until the water evaporates, then stain with 

 fuchsin or methyl violet, clear in xylol, and mount in balsam. 



( To be Continued.) 



Apparatus for Holding Cover-glasses and Cells in Position. — A 

 useful and simple piece of apparatus, that the students make for themselves, is 

 used for fixing cells, cover-glasses, etc. It consists of an oblong board (A) 



of well-seasoned mahogany measuring 12" x 9" 



/-^^ ^^ ff /^ ."^^ \^ X Yi^" , down the center of which a strip of wood 



/—//—/[ — jf — \\~\X~^ ^^ °^^^ '\x\c^ wide by three-eighths of an inch 



/ ^ — — ~ s — s — X thick has been glued. Across the slip (B) is 



' arranged, at right angles, a series of straight pieces 



of watch spring about four inches in length, to the extremities 



of each of which a small circular pad of felt one-eighth of 



an inch thick is affixed. These springs are kept in place 



by laying a second strip of wood along the top of them and fastening them ta 



B b)'^ means of screws. J. H. Cooke. 



London, Eng. 



