Harring and Myers—The Rotifers of Wisconsin. 655 
cover with an inverted watch glass to keep out dust until the 
jelly sets; then trim the jelly with a scalpel as close to the roti¬ 
fers as possible, leaving them oriented in a small block of the 
hardened jelly. Next place a drop of the warmed jelly in the 
center of a round cover glass, invert it and place it in position 
on the mount. As the glycerine jelly containing the rotifers is 
set, this operation will not disturb their position or crush them. 
Apply gentle heat for a moment until the jelly spreads to the cir¬ 
cumference of the cover glass. Lay the mount aside until the 
jelly is set; then remove the excess with a camers-hair brush 
moistened in water. Do not attempt to wipe the mount with a 
cloth before it has been ringed, but use the moistened brush and 
let the moisture surrounding the cover glass evaporate; then re¬ 
wipe with a brush moistened with alcohol until all traces of jelly 
are removed. After the first ring of cement hardens, the mount 
may be gently wiped with a cloth before applying the succeeding 
rings. 
If the Cobb slides are to be used for glycerin mounts, the roti¬ 
fers are mounted on a 25-millimeter-square cover glass on which 
a cement ring of the necessary thickness is spun and allowed to 
dry thoroughly. The cover glass is now fastened to a larger and 
thicker piece of glass by pressing it down hard on a small drop 
of water and wiping thoroughly; this will hold it in place and 
also prevent breakage during the mounting operations; the cover 
is too small and fragile to be easily handled and moved about on 
the stage of the dissecting stand. A small drop of glycerin is 
placed in the center of the cement cell, and the rotifers are trans¬ 
ferred to it with the aid of the mounted bristle. Another small 
drop is next deposited directly on the cement ring of the cell, and 
a round cover glass a little smaller than the outer edge of the 
cement ring is lowered on this drop and pushed over the roti¬ 
fers. If there is not enough glycerin to fill the cell, more should 
be added as minute drops on the end of the bristle as the cover 
is pushed along; care should be taken not to use too much, but 
just sufficient to fill the cell. After the cover glass is in place, 
the excess glycerin, if any, should be removed with a small piece 
of filter paper laid flat over the mount and pressed down gently 
around the edges. Unless a considerable excess of glycerin has 
been used, this gentle pressure will not disturb the position of 
the cell contents to any great extent. The edge of the cover glass 
is now carefully wiped with a moistened cloth, holding down one 
