84 THE AMERICAN MONTHLY [Mar 
alcohol and mixed with 100 c.c. of two-per-cent acetic 
acid.) At first this dye is yellow in color, but if allowed 
to stand it will turn red, and its staining power will in- 
crease. (3) Washing in water. (4) One-per-cent aqueous 
solution of potassium permanganate, for from ten to fif- 
teen minutes. (5) Washing in water. (6) Two-per-cent 
solution of oxalic acid. The drops of fat stain a grayish 
violet, the surrounding portions of tissue being complete- — 
ly decolorized. If this is not the case, the decolorization 
may be repeated after a trial section has been examined 
under the microscope. If it is desired to counter-stain 
the tissues, strong solutions of carmin for twenty-four 
hours will give good results.— Vratch, Sept. 23, 1900. 
THE PRESERVATION OF DeEsMIDS.—The late Mr. W. H. 
-Walmsley’s plan was as follows: Having been perfectly 
successful in preserving the color in many of our fresh- 
water algw, it may be that the same method would prove 
‘successful with desmids. My plan is simply to have a 
‘wide-mouthed bottle, with glass stopper, filled with dis- 
tilled water, in which I have a number of pieces of cam- 
phor. When it is desired to mount the alga,I place a por- 
tion of the same in some of this camphorated water. to 
which a few drops of glycerin have been added, ina watch- 
glass. At first it will become lemon yellow, but after a 
few hours the original green returns in its full vividness, 
then I mount in a shallow cell with a portion of fluid. 
MICROSCOPICAL NOTES. 
Pathogenic Bacteria. An extended reprint of Dr. Dob- 
son’s article on Bacteriology in our January number is to 
be found in the English Mechanic and World of Science, 
of April12. The article was a review of McFarland’s 
Pathogenic Bacteria. The publishers W. B. Saunders & 
Co., have a London branch at 151 Strand W. C. where 
the work can be purchased. 
