1022 General Notes. [October, 
posited in white silky cocoons, which are attached to the under 
side of loosened bark, fence boards, and other sheltered places. 
They are very abundant in September and October, and during 
the entire winter cocoons may be found with eggs in early stages 
of development. This species thrives well in captivity, so that 
there is no difficulty in obtaining eggs freshly laid. 
For studying the egg in a living condition the long-used 
method of immersion in oil is excellent. The oil should be per- 
fectly clear and odorless. The external features can be studied 
to better advantage by mounting the eggs in alcohol after they 
have been freed from the chorion and stained. Another valuable 
method for surface study consists in clearing the already stained 
egg in clove oil. The thickness of the blastoderm is most easily 
determined in this way. 
The best method of hardening preparatory to sectioning is that 
of heating in water to about 80° C., and then, after cooling slowly, 
treating with the usual grades of alcohol. Good results were 
obtained with Perenyi’s fluid, which rendered the yolk less brit- 
tle. Osmic acid does not penetrate the chorion, and chromic 
acid or acid alcohol are not easily soaked out on account of the 
thickness of the chorion. š 
Borax-carmine proved, on the whole, to be the best staining 
fluid. It is difficult to make the dye penetrate the chorion, and, 
after hatching, the cuticula forms a similar obstacle. This iffi- 
culty. may be overcome by prolonged immersion in the staining 
fluid. In some cases seventy-two hours were required to obtain 
a sufficient depth of color. In order to avoid maceration, which 
would result from so long continued immersion in a weak alco- 
holic dye, the staining process may be interrupted at the end of 
every twenty-four hours, by transferring to seventy per cent alco- 
hol for an hour or more. 
After most methods of hardening, the yolk becomes very brit- 
tle, and the sections crumble. This difficulty may be overcome 
by collodionizing the cut surface before making each’ section, in 
the manner described by Dr. Mark (Amer. NATURALIST, June, 
1885)\— Wm. A. Locy. 
Tae Rockine Microtome.\—The Cambridge (Eng.) Scientific 
Instrument Company have just introduced a new type of micro- 
_tome, in which the sliding movement of parts is replaced by a 
=~ Totary one. The ribbon of sections falls by its own weight direct 
= trom the razor on to a sheet of paper. The instrument is simple 
~ on and is sold at the comparatively moderate price 
Of $26. 
_ The chief. objection to this microtome is, that it is adapted to 
only one mode of section-cutting, namely, that of producing rib- 
rn. Roy. Mic. Soc,, June, 1885, p. 549. 
sections imbedded in paraffine. It could not be used for- 
. 
