THE Microscope. 89 
Cottectine SaLt- Water Sponces.*—W.B. Hardy gives the follow 
ing instruction in regard to sponge collecting: The collector should 
be on the ground an hour before the tide begins to rise, and choose 
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. Here will be found 
attached to the under surface of inclined stones, and in the clefts of 
the rocks, on seaweed, and in any sheltered spots where there is good 
surface for attachment and where the sun does not strike too strong- 
ly,—tenacious masses of sponge,—yellow, green, brown, or orange 
color, and with large orifices on the surface. The most common is 
of a sponge-yellow color, shading into green on exposed parts. This 
is the Halichondria panicea, or “bread crumb” sponge of Ellis. 
Another common form, of a salmon color, is Hymeniacidon sangut- 
nea. Pieces of the sponge should be removed as carefully as possi- 
ble and taken home in a considerable quantity of fresh sea water. 
For examining the specimen in the study of its anatomy, a 
pocket lense, a couple of teazing needles, a pipette, and a microscope 
with a few slips and cover glasses will be required. 
EMBEDDING IN Pararrin.t—Dr. Geo. A. Piersol says that while the 
turpentine-paraffin method so commonly employed in histological 
work yields excellent results, the advantages of chloroform-paraffin 
has led to its exclusive adoption in the laboratory of the University of 
Pennsylvania. It is very desirable to secure homogeneity of the paraf- 
fin after embedding,—and for this purpose the method of Kolliker is 
employed. In this the cell containing the object and melted paraffin 
is surrounded with cold water to the upper surface, which alone is” 
left exposed, being cooled by blowing until a film is formed, when 
the whole is submerged. The best paraffin is that commercially 
known as winter-worked gum stock, and comes in cakes about 4 cm. 
thick; that having a bluish tint, and emitting a metallic ring when 
struck, is the best. 
/ 
Srarnine THE Wats or Yeast-Piant Cexts.{—In demonstrating 
the two membranes of the cell of the yeast-plant, Vines found that by 
staining the cells first in methyl-violet, washing in distilled water 
and then transferring to aniline green for some hours, in some 
instances the inner membrane appears of a violet color, while the 
inner layer takes a slight green. 
, * Hardwick’s Science Gossip, January, 1889, p. 11. 
+University Medieal Magazine, December, 1888. 
+ Journal of Microscopy, January, 1888, p. 12. 
