8 
\V. F. ITHCELl,. 
do as well) lor one lionr, tlie alcoliol Leiiig changed several 
times, then for one to two hours in 78 per cent, alcohol, and 
finally in 93 per cent, and absolute alcohol. Chlorofoim was 
used for embedding in paraffin and the sections were stained 
on the slide in alum carmin, wdiich I found the most suitable 
for them. 
. A number of embryos were also preserved in a hot aqueous 
solution of corrosive sublimate (concentrated at the ordinary 
temperature) for the purpose of control. I did not, however, 
require to make much use of these embryos, Avhich could not 
compare with the others in point of preservation. 
The great disadvantage attached to the use of plain hot 
water or hot aqueous solutions, which ai'e the methods 
hitherto usually employed in spider embryology, lies in the 
cii’cumstance that the embryonic tissues take the appearance 
of a syncytium when so preserved. It accordingly becomes 
difficult to distinguish between two or more e})ithelia in con- 
tact, the several layers of nuclei being then usually the only 
feature by which the nature of the tissue can be guessed at 
rather than recognised. 
I devised the hot alcoholic sublimate method desenbed 
above only after repeated experiments. It has the merit of 
rendering the contours of the cells much more distinct, so that 
not only the boundary line between ttvo epithelia in contact, 
but generally also the boundary lines between adjacent cells 
within an epithelium becomes recognisable. 
In the sections these cell-contours may appear iu the form 
of hue dark lines or they may be indicated meiely by a 
difference in the staining between the protoplasm of adjoining- 
cells or by the presence of paler lii.es between the cells, as if 
these had been slightly drawn apart. 
As the appearance of the protojilasm was of minor imjiort- 
auce, but the contours of the ejiithelia and their cells of the 
greatest importance iu my investigations, 1 have for con- 
venience represented tlie contours in the figures by dark lines, 
by which, of course, I do not intend to imply that regular cell- 
walls are present. 
