Limits oF DIVISIBILITY OF Living MatTrER 3829 
subjected to the same treatment with dilute sea-water as the 
pieces which are about to be described. Fig. 80 is a double 
embryo which had arisen from a bursted egg. The two 
embryos are unequal in size, and the larger is ahead of the 
smaller in development in so far as a deposition of needles of 
calcium carbonate has 
begun in the latter. 
Both, however, are 
less developed than 
the pluteus which has 
arisen from a whole 
egg. Fig. 81 arose | 
from a fragment FIG, 86 
which was smaller 
than half the egg of 
Fig. 73. It is an 
early gastrula stage. 
Figs. 82 and 83 are 
still smaller frag- 
ments of an egg, 
which have, however, 
reached only the blas- 
tula stage. These ex- 
amples are not 
especially selected, 
but they represent 
FIG. 84 
only what the observ- 
er will find in any sample from such a culture. 
Do these small pieces develop to the pluteus stage? Two 
days later I found the conditions in this culture as shown in 
Figs. 84-87. Fig. 84 is one of the smallest fragments living 
at this time. It is only a blastula. Fig. 85 represents a 
larger piece in the gastrula stage, but without any evidence 
of askeleton. Fig. 86 shows the smallest pluteus; Fig. 87, 
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