OUR BOOK SHELF. Ig! 
obliquely), and you will find the juice of the plant forming a half 
drop on the cut end. Set the table in motion without delay, and 
place the drop on the cut end, upon the centre of the slide slowly, 
moving it outward as the table turns, so that it shall not twice pass 
over the same spot, until you have formed a scroll-like circle with 
the juice, of about a quarter of an inch in diameter. Let the slide 
remain fifteen or twenty minutes, place a drop of fresh balsam 
upon the centre, and place upon it a half-inch cover-glass. Let the 
cover sink down slowly until it is in contact with the balsam, 
throughout. If not level, press it gently, so that the balsam shall 
fill out handsomely. Set it away, but do not heat it. It will re- 
quire some time to harden, but if in haste to use it, as soon as the 
balsam at the edge of the cover has hardened somewhat, run a 
circle of a solution of shellac in alcohol, so as to touch both the 
edge of the cover and the slide. This will hold all fast, even though 
the balsam be still liquid within. Finish this if you choose, at 
once, and your slide is done. Examine the slide by oblique (black 
ground) light, or far better, if you have it, by polarized light. Use 
the green, not the purplish coloured, ‘spider-wort,” and you will 
find the needles beautifully distributed, clean, and looking like 
polished steel. The needles are oxalate of lime, and are beautiful 
with polarized light—American Monthly Microscopical Journal, 
OUR BOOK SHEEP 
A Synopsis of the Fresh-water Rhizopods. ROMYN HITCHCOCK, 
F.R.M.S. New York: 51, Maiden Lane. Pp. 56. 
That elaborate work, “The Fresh-water Rhizopods of North 
America,” compiled by Professor Joseph Leidy, and published by 
the United States Government, not being within the reach of every 
one, we welcome this little treatise which the author believes will 
in most cases enable the student to name the specimens that he 
has collected without the aid of figures, This is so: the orders, 
sub-orders, and genera are all accurately and minutely described, 
still the student must have made considerable progress ere descrip- 
tions only render him infallible in his nominations. 
The following description of the Genus Amceba will show how 
this has been performed :— 
Genus I.—AMCBA. 
“When at rest, a spherical or oval mass of soft, hyaline, colorless, 
granular protoplasm. When in motion, form variable. Ectosarc 
hyaline and minutely granular, endosarc continuous with the former, 
