168 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
normal sea-water after 180 minutes practically all disintegrated 
into droplets and only a few developed. Not a single one of the 
eggs which had been in the hypertonic solution in an atmosphere 
of hydrogen developed when transferred to normal sea-water 
after 128 and 180 minutes. The eggs appeared quite normal 
and that they were really so is shown by the fact that they 
developed normally upon the addition of sperm. 
In these experiments, of course, not all the oxygen had been 
expelled from the hypertonic solution, but the pressure of the 
oxygen had been depressed below the minimum necessary for 
the developmental effect of the hypertonic solution. 
We will mention one further experiment. Unfertilized eggs 
of a female were divided among five flasks, each of which con- 
tained 50 c.c. of sea-water+8 c.c. 25m NaCl. One flask was 
left open, 1.e., exposed to the air; the others, out of which the 
air had been driven by passing hydrogen through them for two 
hours, remained connected to the stream of hydrogen. After 
2, 3, 43, and 53 hours, one of the flasks was disconnected from 
the hydrogen apparatus, and the eggs contained in it were 
transferred to normal aerated sea-water. They were abso- 
lutely unaltered and did not divide or develop. On the 
addition of sperm! they all segmented and developed normally, 
thus showing that they were really, not- only apparently, 
unchanged. Simultaneously a sample of the eggs from the 
aerated hypertonic sea-water was also immediately transferred 
to normal sea-water. The eggs transferred from this hyper- 
tonic to normal sea-water after two hours yielded a good number 
of normal blastulae. Only about 1 per cent of the eggs, trans- 
ferred from the aerated hypertonic to normal sea-water after 
three hours, developed; the rest disintegrated into small drops. 
Those removed after 45 and 53 hours all went to pieces in the 
same way. We can now understand another phenomenon 
1 The sperm should not be added until about an hour after the eggs are 
replaced in oxygenated sea-water; otherwise the results are not so good. 
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