ARTIFICIAL PRODUCTION OF NoRMAL LAarRv#& 591 
Ill IS IT POSSIBLE TO PRODUCE BLASTULE FROM UNFERTI- 
LIZED EGGS WITHOUT RAISING THE CONCENTRATION OF 
THE SEA-WATER ? 
The early experiments with which I started had indicated 
that an increase in theconcentration of the sea-water caused the 
segmentation of the nucleus in the fertilized egg. Morgan’s 
experiments had shown that the same influence may cause 
the unfertilized egg to show a beginning of segmentation. 
In Mead’s experiments, however, there was practically no 
increase in the osmotic pressure of the sea-water, while the 
nature of the ions seemed to determine the result. I wished 
to find out whether a blastula could be secured from an 
unfertilized egg without raising the concentration (the total 
osmotic pressure) of the sea-water. All my experiments 
thus far have yielded the result that this is impossible, and 
that by this method only a beginning of a segmentation can 
be produced in an unfertilized egg. It goes without saying 
that in these experiments bacteriological precautions are 
necessary to guard against the possibility of the introduction 
of spermatozoa by the instruments, or of their presence in 
the sea-water. One has a pretty reliable criterion for the 
entrance of a spermatozoon into the egg of Abacia in the 
formation of the egg membrane. An unfertilized egg has 
no distinct membrane, but immediately after the fertilization 
avery distinct and rather thick membrane is formed. As 
none of the eggs in the following experiment formed a mem- 
brane or showed more than the beginning of a segmentation, 
we may reserve the discussion of our methods of protection 
against fertilization for the next section. Unfertilized eggs 
of the same female were divided into three lots. One was 
put into a solution of 96 cc. §n NaCl+2 cc. $n KCl+ 
2c.c. 10n CaCl,. After three and one-half hours a few of 
the eggs showed a beginning of segmentation. After eight 
hours a majority of the eggs had divided into from 2 to 4 
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