1895,] Microscopy. 195 
supply of these little pith filters can be cut and kept in stock in a pill- 
box, ready for use at any time. 
The next step is to take some ordinary good white filtering paper, 
cut into disks or squares about one inch in diameter. With a small 
drop of water on the end of a wooden toothpick, moisten a point at the 
centre of one of these paper disks or squares, so as to make a damp 
area just about the area of one of the disks of pith. Then take a wire 
1-16 inch thick, heat one end, and with its help place on the paper 
disk or square some melted paraffine. This may be heated with the 
hot wire so as to saturate the whole of the paper disk or square, except 
the central moistened spot, which must be left unsaturated with paraf- 
ne. 
The next step is to prepare a discoidal pad about one inch in diame- 
ter, composed of 10 to 20 superposed thicknesses of filter paper. Upon 
this the disk or square of filter paper, with all but the central spot 
saturated with paraffine, is superposed. I find that the ordinary extra 
large live-box or compressor, provided with a mica cover, with a round 
perforation of $ inch in diameter in its centre, is an excellent device 
for holding the disk prepared with paraffine down upon the thick pad 
of filter paper. The accompanying figure, showing the complete ap- 
a ee 
paratus in vertical section, will perhaps make the arrangement of its 
parts clearer. The cap-ring C of the large-sized live box or compressor 
holds the perforated mica cover m m in place. This perforation should 
be a little larger than the disk of pith e, immediately below which lies 
the disk of filter paper f, which issaturated with paraffine except at its 
centre. Then follows the pad of several thicknesses of filter paper P. 
The mode of operation is as follows: Place P upon the glass disk g of 
the live box or compressor; then lay f upon P; then put the cap C 
with its centrally perforated mica cover mm in place and slip it 
