THE MICROSCOPE. era 
_ the terminal spines ; radiating striee coarse, moniliform, and divided 
towards the margin of valve, where they are again divided and 
intercalated by short, marginal ribs.” 
The position of the genus as a spined, discoid form, seems to 
me to be pointed toward the family Eupodiscez, which includes 
forms from which Raphidodiscus is only separated by the presence 
of the raphe, and I would place the genus adjoining Awlacodiscus 
or Hupodiscus. 
CLEVELAND, OHIO. 
MOUNTING IN GLYCERIN OR OTHER FLUIDS. 
J. D. KING. 
T makes but little difference what kind of cement is used for cells 
for glycerin mounts if it adheres well to the slide, does not 
erack or crumble, and is allowed time to harden so that it will not 
spread or runin. If tin cells are used they should be covered with 
a thin coating of cement, otherwise the glycerin will combine with 
the metal and precipitate a white cloud in the cell. 
Make the cell not less than two and half mm. in width. Let 
it harden till it cannot be impressed with the thumb-nail, and file 
the surface to an even bearing down to two-thirds the width. A fine 
single-cut file is best, because it can be easily kept clean with a stiff 
brush. 
Be sure the cell is deep enough so that the cover glass will come 
down to the even surface of the ring without too much pressure on 
the object, otherwise it will be difficult to seal it. Centre the slide 
on the turn table, and cover the outer half of that surface of the cell 
which has been filed with any strong, colorless cement, but if laid on 
too thick it will be liable to run off and make a mess. 
Place the object in a sufficiency of glycerin just to round up 
the surface a little above the top of the cell, being careful not to run 
it over ; too much fluid will be likely to drive out the object besides 
disturbing the layer of fresh cement. Select a cover glass large 
enough to cover the entire filled surface of the cell; breathe on the 
cover glass, or what is better, dip it in camphorated glycerin, or 
glycerin and water, to escape air bubles ; place the cover and secure 
it with a clip ; shake off the overflow of fluid and leave the slide a 
few hours for the cement to set, when it can be safely washed off 
under the tap, wiped perfectly dry and sealed. 
The troublesome leaking of glycerin cells is due in part to the 
penetrating character of the fluid, and partly to its expansiveness 
