
THE GASTRULATION OF THE EGG OF BUFO 
LENTIGINOSUS. 

HELEN DEAN KING. 
AN examination of the literature dealing with the early 
development of the amphibian egg shows many conflicting 
observations and theories regarding the origin of the blasto- 
pore and the manner of formation of the mesoderm and 
notochord. It is evident, therefore, that more forms must be 
studied and the observations in some cases carefully repeated 
before any general conclusions regarding the origin of these 
structures can be drawn for the entire group. 
The amphibian eggs that have been most studied are those 
of Rana, Triton, Axolotl, and Bombinator. The present paper 
deals with the early development of the egg of Bufo lentiginosus 
from the end of cleavage until the closure of the blastopore. 
The eggs of this amphibian, although very abundant and easily 
obtained, have been but little used either for observation or for 
experiment, owing, doubtless, to their small size and to their 
relatively deep pigmentation, which makes it very difficult to 
follow the fate of living cells. 
METHOD. 
In preparation for sectioning, eggs were killed in various 
fluids: picro-acetic, picro-sulphuric, formalin, and corrosive- 
acetic. By far the best results were obtained with corrosive- 
acetic (5 per cent acetic). Formalin (3-10 per cent) gives 
exceedingly good preparations for a study of surface struc- 
tures, but it cannot be relied on to give histological details, 
as it usually produces numerous cracks in various parts of 
the egg. The sections were stained on the slide with the 
mixture of borax carmine and Lyon's blue, recommended in 
a previous paper (King, 10). With the use of this stain the 
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