26 Transactions of the Society. 



adjusted. Tilt the slide and allow the superfluous oil to run off. 

 Drop on the smallest quantity of xylol, and then add the balsam 

 (xylol-balsam). Leave it a few minutes and apply a warmed cover- 



glass. 



If the specimen will admit of it, lift it on to a clean cover-glass 

 with a brush. Apply the xylol and balsam. Lower a slide down 

 on to the balsam, and turn over. It is always better to mount on 

 the cover-glass for research with immersion lenses. 



When cocaine is used, pass osmic through and treat as described. 

 Floscularia will require three days in the osmic and stain. When 

 picric acid is used, leave the forms in it for a while and add picro- 

 carmin. 



Protista require about 8 hours in the moist chamber; 24 hours 

 are generally necessary to exhibit the cilium. 



Before washing with water, when picric is used, pass under the 

 cover-glass a few drops of osmic. Then proceed with water, then 

 alcohol, and then oil as described. 



For Euglena I use formalin, picric, or osmic to fix and harden, 

 5 to 10 hours. Osmic alone preserves the natural colour of many 

 EiajleiKC and Diatoms. 



For the Study of Cell-division in Diatoms. — The following 

 method not only fixes the cell contents, but emphasizes the beau- 

 tiful markings. The diatoms are put into a watch-glass in sea- 

 water or fresh-water, according to their habitat. Place a small 

 piece of wet cotton near the edge, move the watch-glass round, and 

 the diatoms gather at the bottom. Slowly tilt the watch-glass to 

 pour off the liquid, helping it away with blotting-paper. The 

 cotton prevents the escape of specimens. 



Now fix with abundance of picric acid or osmic, add picro-carmin, 

 cover with another watch-glass, and leave in the dark for ten 

 hours. Then pour off the picric as before, by tilting and blotting- 

 paper. Add water, and pour off again. This is repeated until no 

 colour is given off. Go through the same process with absolute 

 alcohol. 



When no colour is given off, leave the specimens in the alcohol 

 some hours, covering with a watch-glass, which will prevent rapid 

 evaporation. Dip a brush now in the watch-glass, lift a few 

 specimens, and transfer to oil of cloves on a slide. If they clear, 

 the rest of the specimens are ready. When that is so, pour off the 

 alcohol and add oil of cloves. 



Leave the specimens in the oil for a while, and lift out as 

 required with a brush on to a cover-glass. Drop on them the 

 smallest quantity of xylol, then drop on the balsam. Leave the 

 cover-glass thus, protected from dust, for a while, then "turn over 

 the cover-glass on to a slide just moistened with xylol. 



This method may be adapted to preparing quantities of Rotifers, 

 and is very useful for the larger Protista. Minute Protista are 



