260 STUDIES IN GENERAL PHYSIOLOGY 
solution for a few hours with spermatozoa that had been 
under the same conditions, only about one egg in a million 
began to show some trace of segmentation, and as a rule this 
segmentation remained in statu nascendi, but was not accom- 
plished. All these observations are totally different from the 
phenomena described above. Eggs which had been fertilized 
in normal sea-water, and which were put into the concen- 
trated solution, after being brought back into normal sea-water 
for from ten to twenty minutes segmented without any excep- 
tion, and were able to develop into normal blastulae and plutei. 
Eggs of this kind were still able to develop into normal 
larvee after having been in the concentrated solution for four 
to six hours. But eggs which before impregnation had been 
put into the concentrated solution together with spermatozoa, 
and which four to six hours later were brought back into nor- 
mal sea-water, reached only the first stages of segmentation, 
if they segmented at all, and then stopped developing. I 
never got a living larva from these eggs. From all these 
facts I conclude that the continual increase of the nuclei of 
the impregnated eggs in the concentrated solution was due, 
not to polyspermia, but simply to segmentation of the nucleus. 
In these experiments bacteriological precautions are neces- 
sary, as the water of the aquarium is liable to contain quan- 
tities of spermatozoa. 
7. From the above I believe to have shown that by bring- 
ing fertilized eggs of sea-urchins into more concentrated sea- 
water —we added 2 to 2.4 g. of NaCl to 100 e.c. of sea-water 
—the segmentation of the nucleus proceeds, although more 
slowly than under normal conditions, while no segmentation 
of the protoplasm is possible. The fact in itself is of some 
technical value, as it enables us to separate two processes 
which nature generally produces together, or which hitherto 
we had not the power to separate at desire. In regard to 
our knowledge of segmentation, we see from this that the 
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