EMBRYOLOGY. 95 
METHODS AND MATERIAL. 
The material used in this investigation was collected in the autumn 
of 1908 at Richmond, Ind., and in 1909 and 1910 at La Fayette, Ind. 
The eggs were killed and fixed mainly in two solutions that are practi- 
cally the same. The first was a saturated solution of bichlorid of 
mercury (corrosive sublimate) in 35 per cent alcohol, 95 volumes, 
and glacial acetic acid, 5 volumes. The second was a saturated 
solution of bichlorid of mercury in 50 per cent alcohol, 94 volumes, 
and glacial acetic acid, 6 volumes. The fixing fluid was raised to a 
temperature of 75° to 80° C, poured over the living specimens, and 
allowed to act from 5 to 10 minutes, after which it was replaced by 
the same solution, cold, for an equal length of time. The specimens 
were then washed in 70 per cent alcohol, in which they were kept 
until sectioned. Gibson's fluid was found to be a very good killing 
and fixing agent also. 
For sectioning, the following method was employed: The eggs 
were punctured with a fine needle, dehydrated, and kept 20 to 
30 minutes in paraffin of about 54° C. melting point. They were 
oriented in a watch glass (that had previously been smeared with 
glycerin) with a hot needle, under a binocular microscope, the bottom 
of the watch glass being first quickly cooled with a little cold water. 
The eggs were cut with a Minot-Zimmermann microtome in 
sections from 8 to 13 /z in thickness, attached to the slide with Mayer's 
albumen fixative, and stained with Delafield's hematoxylin or by 
Heidenhain's iron-alum-haematoxylin method. 
Surface views of the embryo were obtained by dissection. For 
dissections it was found that the best results were obtained by using 
material that had been freshly fixed and washed. Grenadier's 
alcoholic borax-carmine was used for staining in toto. 
GENERAL DESCRIPTION OF THE EGG. 
The eggs are broadly elliptical with* a slight reniform tendency. 
They are 0.70 to 0.78 mm. in length and 0.33 to 0.45 mm. broad. 
At oviposition the egg is a very pale yellow, changing in a few 
hours, at a temperature of 50° to 70° F., to a faint greenish color. At 
this stage there appears an almost circular area of darker green at one 
pole of the egg; we have termed this the "ovarian yolk," a brief 
description of which occurs in the following pages. At the end of 24 
hours the walls of the egg about the ovarian yolk appear denser 
and of a deeper green. The germ band is now forming and invaginat- 
ing. During the next 24 hours this process is completed, the egg 
becoming a darker green in the meantime. By the third day a rod- 
shaped body can be seen near the center of the egg. This object is 
the submerged germ band. By the end of the third day the egg 
becomes black. 
