328 STUDIES IN GENERAL PHYSIOLOGY 
may begin to segment somewhat later than the rest of the 
egg. The influence of the quantity of the egg-substance 
upon the formation of the gastrula is, however, an unques- 
tionable one. The substance which remained within the egg 
has developed in Fig. 77, twenty-four hours after fertiliza- 
tion, to the gastrula stage. According to Fig. 75, its mass 
is about twice as great as that of each of the two blastule 
which arose from the extraovate, and which at this time had 
FIG. 80 
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FIG. 79 FIG. 81 FIG, 82 FIG. 83 
not yet reached the gastrula stage. I have observed this 
over and over again; as, for example, in Fig. 78, where the 
small extraovate b has formed a blastula, while the rest of 
the egg « has formed a gastrula. The cultures kept in a 
drop of water always died in the course of the second or 
third day. The large pieces reached the pluteus stage dur- 
ing this time, while the smaller pieces remained in the blas- 
tula or gastrula stage. In order to follow the further fate of 
these small fragments of the egg after the second or third 
day, I had to rely on the material from the cultures kept in 
the larger dishes. Figs. 79-83 represent the relation between 
mass and development in a culture two days old. Fig. 73 
shows the size of a fertilized but undeveloped egg of this 
culture two days old; Fig. 79, the size of a pluteus that had 
developed from an entire egg, which, however, had been 
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