284 THE MIcRoscoPE. 
the distilled water on the cover. Owing to the rapid motion 
produced by the union of the water and the alcohol the Diatoms 
are scattered over the glass. The metal table is then heated, 
but so gently as to avoid boiling the water, and the Diatoms 
subsequently mounted in the usual way. 
COLLECTING SALT-WATER SPONGES.—Mr. W. B. Hardy recom- 
mends} that the collector should start about an hour and a half 
before low water, so as to be on the ground a full hour before 
the tide commences to rise again, and choosing some sheltered 
nook among the rocks if the coast be a rocky one, or about the 
piles of a pier if it be an open one. There he will be sure to 
find attached to the under surface of inclined stones, in clefts 
and cranies of the rocks, about the roots of the sea-weed, in 
short, in any sheltered spot where there is a good surface for at- 
tachment and where the sun does not strike too strongly, tenaci- 
ous masses of a sponge-yellow, green, brown, or orange color, 
and with large orifices on the surface. These are the easily re- 
cognized objects for which search is being made. 
Pieces of the sponge should be removed as completely as pos- 
sible and taken home ina considerable quantity of fresh sea 
water. A pocket lens, a couple of needles mounted in holders, 
a pipette, and a microscope with a few cover glasses and slips 
are all that is required for the first examination. 
A sponge is composed of sponge flesh supported by a skeleton. 
The latter is composed of a network of delicate needles, gathered 
into interlacing bundles; the sponge flesh forms a mass which 
contains imbedded in it the skeleton, and is also honeycombed 
by a system of canals and spaces, all in complete intercommuni- 
cation, the canal system. One extreme of the canal system is the 
pores, the other the oscula; and through it a continual stream of 
water is flowing during the life of the animal, setting in from the 
pores to the oscula, The current is maintained by the action of 
flagella situated on the cells lining certain enlargements in the 
course of the canals, known as the flagellated chambers. 
METHOD OF INVESTIGATING cycLops.*—In his researches into 
the morphology of Cyclops, Prof. M. M. Hartog sometimes found 
it necessary to examine live specimens; undue pressure was 
+Science Gossip, Jan . 1889. 
*Journ, R. M.S, From Trans. Linn. Soc. Lond. 
