332 Some Phases of the Gastrulation of the Horned Toad 
from the oviduct of a gravid female immediately after she has been 
chloroformed. The oblong eggs are cream-colored and when laid the 
soft, moist, semi-transparent membraneous shell allows the embryonic 
area to show through, forming a dark pinkish oval area on the upper side 
of the egg. The egg shell becomes tough on drying, but not brittle or 
stiff. To fix the embryos free from yolk and separated from the egg 
shell, a disk somewhat larger than the embryonic area was cut out. In 
removing this a considerable portion of the yolk immediately beneath was 
carried with it to sustain the embryo until it could be supported on all 
sides by physiological salt solution. By the careful use of a current from 
a pipette, the yolk was removed and then the shell membrane and the 
vitelline membrane. Sometimes, in very early stages, it was found de- 
sirable to allow the shell membrane to remain on the blastoderm for its 
support. Usually a drawing was made of the unstained embryo with the 
aid of about sixty diameters magnification, in order to facilitate the in- 
terpretation of sections In general, Fleming’s mixture of chromic-aceto- 
osmic acid was employed for fixing followed by successive alcohols. A 
modification of Mayer’s hemalum was found superior to hematoxylin 
and other hematin stains, both for sections and specimens in toto. For 
the latter Mayer’s hemalum diluted with twenty parts of ammonia alum 
was employed. The specimen was decolorized in 1-10 of 1% hydro- 
chloric acid made up in 70% alcohol. Alcoholic cochineal also gave good 
results in toto. Benzopurpurin was advantageous in older stages. Orange 
G was used as a plasma stain in sections. Clearing was accomplished by 
the use of anilin, or clove oil, removed subsequently by xylol 
Owing to the radially symmetrical appearance of the embryonic area 
in the earliest stages, they were extremely difficult to orient. They 
were embedded in celloidin and then the celloidin was pared down until 
the embryos could be observed under the low power of a microscope when 
triangular blocks were cut with definite relation to the anterior and pos- 
terior end of the blastoderm. These were reémbedded when sectioned. 
The celloidin also protected the delicate embryos which had become 
brittle after several years in alcohol. 
The youngest embryo in this collection has passed through cleavage 
and the first phase of gastrulation being in the second phase of gastru- 
lation as first worked out for the lizard by Wenckebach, 91, p. 75. 
This stage is represented in surface view in Fig 1. Superficially it re- 
sembles a like stage of Lacerta viridis, according to the drawings of Will, 
95, b, Fig. 6, Pl. 1; also of the turtle embryo as represented by Mit- 
sukuri, 94, Fig. 1, Pl. 6, and of Tuatara (Hatteria) as figured by Dendy, 
99, Fig. 1. The embryonic area is pushed up above the surrounding 
