898 STUDIES IN GENERAL PHYSIOLOGY 
In order to be able to compare these results with those 
obtained on the Ctenolabrus egg, I repeated the experiments 
on Fundulus, using the same method of replacing oxygen 
by hydrogen, and the same apparatus which had been used 
in the case of the Ctenolabrus egg. 
The results obtained were in entire harmony with our 
earlier findings. When freshly fertilized eggs of Fundulus 
are introduced into the Engelmann chamber, and a vigorous 
stream of hydrogen is passed through it, the eggs divide not 
only once, but continue to do so for fifteen to twenty hours, 
until a blastoderm is formed which extends over the sur- 
face of the egg. The result was the same when the’ eggs 
were put in an Engelmann chamber and kept for two and 
one-half or three hours on ice, during which time they were 
exposed to a vigorous stream of hydrogen. When the eggs 
were then exposed to room temperature, segmentation at once 
began and continued in a regular manner. During the 
entire course of the experiment hydrogen was permitted to 
pass through the chamber. 
As long as the number of the cleavage-cells was so small 
that they could be counted, it could be seen that develop- 
ment without oxygen occurred as rapidly as in oxygen. 
Whether this holds also for later stages when cleavage 
approaches the standstill cannot be determined, as the cells 
are then too small to allow one to count them. Not only 
cleavage, but also growth, of the blastoderm, that is to say, 
increase in area (at the expense of the yolk (?), 1903) occurs 
in the absence of oxygen. The blastoderm grows from a 
small area to a large area on the surface of the yolk. 
If Fundulus eggs are allowed to remain more than twelve 
to fifteen hours in hydrogen, the cells nevertheless do not 
liquefy, as is the case in Ctenolabrus in the absence of 
oxygen. ven after twenty-four hours no such phenomena 
are observable in the Fundulus egg. I have shown in 
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