NOTES ON SOME PARASITIC PROTISTS. 135 
it quite successful :—Hxpose coverslip (carefully cleaned) to 
vapour from 1 per cent. osmic acid thirty seconds; spread 
out small drop of culture on exposed surface, and hold in 
vapour thirty seconds to one minute; harden in absolute 
alcohol ten to fifteen minutes; stain in Giemsa (Griibler, 
1 drop to every c.c. of water) for twenty minutes; wash in 
water; dip rapidly into absolute alcohol; take coverslip 
quickly through three changes of xylol and alcohol (equal 
parts) into pure xylol; when quite clear mount in cedar oil. 
I have obtained equally good results with formalin-fixed 
films treated in this way. And I have also been able to 
make successful preparations in this manner—without drying 
—using as stains Loffler’s methylene blue and corbol-fuchsin. 
Dehydration may also be effected without decolorising by using 
acetone (puriss. acid-free) instead of alcohol (Schridde, C.B. 
allg. Path. u. Anat., xvi, 1905). I have not been very 
successful with this method, but I believe with a little modi- 
fication it could be made very effective. 
Giemsa preparations should be mounted in cedar oil or 
neutral Canada balsam. These preparations are usually the 
prettiest, but I think iron-hematoxylin is more accurate. 
Many other methods may, of course, be used in studying 
Bacteria. I have merely given those which I have myself 
found useful, in the hope that they may be of some use to 
others. 
ZOOLOGICAL LABORATORY, 
CAMBRIDGE ; 
5th September, 1907. 
