306 STUDIES IN GENERAL PHYSIOLOGY 
for example, such as were ruptured in the sixty-four-cell 
stage —did I usually obtain something different, namely, 
abnormally formed skeletons. Nevertheless at times I ob- 
tained under these conditions also real “Siamese” twins. 
4, So far as the theoretical importance of these experi- 
ments is concerned, the following seems certain: As the burst- 
ing of the membranes and the flowing out of the protoplasm 
is a purely mechanical process determined by osmotic forces, 
no reason is at hand for assuming that qualitatively or quan- 
titatively the same constituents leave the egg in each case; 
according to direct observation, the opposite seems to occur 
with much more certainty. Nevertheless, the extraovate 
develops into a complete embryo. It follows from this that 
every part of the protoplasm can form an embryo. So far 
as the nucleus is concerned, the two spheres obtain entirely 
different constituents of the nuclear substance. Nevertheless, 
they develop in exactly the same way to similar embryos, as 
Driesch has already shown by other methods. Thirdly, my 
experiments show that the number of embryos which can 
arise from an egg 1s determined by the geometrical form 
which we give the protoplasm, in so far as each completely 
or almost isolated sphere (or ellipsoid) of protoplasm deter- 
mines the formation of a separate blastula, and as the num- 
ber of blastulee determines the number of embryos. In this 
way I obtained last year double embryos from a normal egg 
when I introduced it, in the two-cell stage, into somewhat 
concentrated sea-water for some time, in which it was unable 
to segment further. When I brought such eggs back into 
normal sea-water, each of the two hemispheres broke up into 
several cells at once. The cells of each of the hemispheres 
probably adhered to each other, but not to the cells of the 
other hemisphere, so that an isolation of the two hemispheres 
was obtained in this way. In one egg I obtained double 
blastule. The method deserves to be worked out more care- 
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