No. 3.] BASIS OF THE AMPHIBIAN EMBRYO. 469 
at frequent intervals. Eighteen eggs developed normally; in 
the remainder, the exovates were so large that either death or 
abnormal embryos resulted. 
In eight eggs (Figs. 1, 2, 6-10, 13) the exovates were later 
found in or near the median plane of the embryo, and in the 
immediate vicinity of the transverse portion of the neural fold. 
In three eggs (Figs. 14, 15, 17) the exovates lay within the 
transverse portion of the neural fold, and at the right of the 
median plane. 
In two eggs (Figs. 11, 12) the exovates were found in the 
transverse portion of the neural fold, and at the left of the 
median plane. 
In one egg (Fig. 18) the exovate was in the median plane, 
but far behind the transverse portion of the neural fold. 
In four eggs (Figs. 3-5, 16) the exovates were entirely with- 
out the embryonic area. Those shown in Figs. 3 and 16 
‘occupied positions which at present are quite unexplainable. It 
is possible, although improbable, that a shifting in the position 
of the exovates occurred. It should be here stated that the 
eggs were examined at short intervals, and the position of the 
exovates, with reference to certain accidental abrasions, care- 
fully noted. 
Other experiments were made by marking various portions 
of the egg in the vicinity of the blastopore. 
Five eggs were selected in the crescentic blastopore stage. 
These were punctured just above the middle of the blastopore, 
as shown in Figs. 19 and 21. Three developed. In two the 
exovates gradually approached the blastopore, and were carried 
within the margin, as shown in Figs. 20 and 22. When they 
came in contact with the yolk mass they were detached. Their 
points of attachment, however, remained visible, and were fol- 
lowed step by step until they disappeared within the blastopore. 
In one egg the exovate passed through the successive steps 
represented by Figs. 28-30, but was not infolded. 
Five eggs were marked at one extremity of the crescentic 
blastopore, as shown in Fig. 23. Only one egg developed. 
The position which the exovate finally occupied with reference 
to the blastopore is shown in Fig. 24. 
