330 WHITMAN AND EYCLESHYMER. [Mor exci: 
of grass or rootlets are placed in shallow watch-glasses and 
held in a fixed position by weighting with small pebbles. The 
watch-glasses are then placed upon a mirror fastened to the 
stage of a dissecting microscope. We could thus observe 
the changes occurring on opposite sides of the egg without 
disturbing its position. 
The fixing fluids which have given the more satisfactory 
results are: Flemming’s fluid, Perenyi’s fluid, chrom-osmic, 
picro-acetic, and picro-sulphuric. For surface views chrom- 
osmic fixation gives most perfect pictures, the osmic blacken- 
ing the cleavage grooves so that they stand out in bold relief. 
Another excellent method is surface staining with Delafield’s 
haematoxylin, which may be employed with any of the above- 
named fixatives. For material which is to be sectioned, picro- 
acetic and Perenyi have given best results. Owing to the 
crumbling of the yolk we have been obliged to use celloidin as 
an imbedding mass. Serial sections by the method described 
by the junior author® have been used for the most part. 
Staining in section with Ehrlich’s haematoxylin and Mayer’s 
alcoholic carmine has proved most satisfactory. 
The freshly deposited egs (Fig..2) is firmlyfixed tovthe 
object with which it first comes in contact by means of the 
threads of the villous layer, which are elongated over the lower 
hemisphere of the egg membrane. The egg is oval in profile 
view, measuring in its longest diameter, including the mem- 
brane,’ 2/5 to 3mm. ; in its.shortest, 2 to 255mm: The upper 
pole of the egg, ‘calotte”’ of Fiilleborn, “ germ-disc””’ of Dean, 
is light yellowish brown. This calotte shades off at its margin 
into the dark grayish brown of the yolk. Near the centre of 
the calotte there is a single micropylar orifice, as shown in 
Figs. 21 and 22, which remains visible for some time (Figs. 12 
and 16). We have frequently noticed that the margin of the 
calotte extends farther toward the equatorial region on one side 
than on the other, as shown in Fig. 2. 
The calotte is already present in the full-grown ovarian egg 
shown in Cut 1. It is not of quite uniform thickness, but is a 
5 A.C. Eycleshymer: Notes on Celloidin Technique. American Naturalist, 
vol. XXVI, pp. 354-358. 
