654 Wisconsin Academy of Sciences , Arts, and Letters. 
glass over the cell. Wipe the four corners of the cover with a 
cloth moistened in alcohol and secure it with a small drop of al¬ 
coholic cement at each corner. In a few days an air bubble will 
appear in the cell and will increase in size until all the water is 
evaporated, which may take several weeks. Concentration will 
have been so gradual that the animals will generally be free from 
wrinkles. The cement may now be scraped from the corners of 
the cover, permitting it to be moved aside, and the rotifers picked 
out and mounted. 
A pipette should never be used for handling rotifers in gly¬ 
cerin, as they will invariably stick to the inside and be lost. They 
are very easily picked up with a rather flat bristle mounted in 
a holder; bristles from an old and much worn tooth brush are 
especially good for this purpose, as the ends seem to wear to just 
the right shape, a wedge-shaped, slightly blunt point. Removing 
a rotifer from glycerin should be done under a dissecting micro¬ 
scope ; the specimen must be brought to the surface and then lifted 
out by getting the bristle under it. If once lifted out, the rotifer 
may be left on the bristle with perfect safety until wanted; slides 
and covers may be cleaned, if necessary, without fear of loss of 
the specimen. Glycerin used for mounting should be removed 
from the bottle by inserting the bristle for its entire length and 
quickly withdrawing; the glycerin will then run down the bristle 
and form a drop, the size depending on how rapidly it was with¬ 
drawn. 
Rotifers may be kept in glycerin for observation and study by 
temporarily mounting them in “stock” slides: cavity slides with 
square covers held at the corners with a drop of alcoholic cement. 
A collection that is in active use is perhaps more useful if mounted 
in this way than in any other. The rotifers may be manipu¬ 
lated in any way by simple scraping the cement from the corners 
and pushing the cover about; if necessary, they can be trans¬ 
ferred to water and put back again. 
All strongly loricated species may be mounted in glycerin 
jelly. No cell is required, and they are mounted directly on 
plain slides or on the 25-millimeter-square cover glasses of the 
Cobb thin slides. Place a very small drop of glycerin in the 
center of one of these cover glasses and transfer the rotifers with 
the bristle. Warm some jelly until it is of about the same con¬ 
sistency as the glycerin and place a drop directly on top of the 
glycerin drop containing the rotifers. Orient the rotifers and 
