NATURAL HISTORY MISCELLANY. 441 
be mounted in Canada balsam, when it shows all its beauties in a re- 
markable manner, and, at the same time, shows its effects on polarized 
light. I would say, that the potassa cleans the shell and operculum 
beautifully. — A. M. EDWARDS, New York 
THE MOVEMENTS OF THE DIATOMACEÆ.—The movements of the - 
Diatomacee still continue to puzzle microscopists, and various expla- 
nations of this phenomenon have been advanced. Professor Schultze 
as carefully studied a number of species, Pleurosigma angulatum, 
Pleurosigma fasciola, Nitschia sigmoides, Surirella bifrons, and others, 
maki eriments and observations upon them e ed 
from these researches to conclude that a glutinous organic substance, 
which is concerned rapi vement, is spread over the external 
Bacillarie become adherent to one another. Professor Schultze does 
not consider that this view affects the question of the animal or plant 
other unicellular beings, as of ‘‘uncertain kingdom,” until we know 
more of what constitutes the boundary, if there be any, between plants 
and animals. — Quarterly Journal of Microscopical Science. 
a 
ANSWERS TO CORRESPONDENTS. 
J. T. M., Grand Isle, Vt.—The land snails sent for identification 
are follows: The “largest, No. 1,” is Helix concava Say. 
“horn-colored, No. 2,” is Helix chersina Say. The “small reflected 
lipped, No. 3,” is Helix minuta Say. The ‘light-colored conical-shaped, 
very favorable time for collecting, as the leaves, having fallen, no 
longer obstruct the light, and the snails can be easily detected by turn- 
ing up the damp layers in hard-wood growths. r 
D.S. C., Rockport, Ill. — “Essay on Classification,” by Professor 
Agassiz, was published separately in London; Longmans & Co., 1859. 
You can undoubtedly obtain it by ordering of any prominent bookseller 
in New York. The cheapest form of cabinet for geological specimens 
is an upright case of shelves, like a bookcase. The shelves to be in- 
clined, or to have separate steps on each shelf. For a conchological 
case, make a set of shallow drawers, 18x24 inches, and from two to 
five inches deep. For exhibition, nothing is better than a horizontal- È 
Show-case, though this takes up a great deal of room. 
E. L. M., New York.—Besides the works on Entomology already 
mentioned in the NaTuRaList, you need the works on American 
AMERICAN NAT., VOL. I. 56 
