PHYSIOLOGICAL Errects oF Lack oF OxyGEen 397 
supplied to them. We found before that a lack of oxygen 
does not retard cleavage as long as cleavage is at all possible. 
In the same way an excess of oxygen does not accelerate the 
process. 
VIII. EFFECT OF LACK OF OXYGEN ON THE CLEAVAGE OF 
THE FUNDULUS EGG 
The eggs of Ctenolabrus have a lower specific gravity 
than sea-water, and therefore float at the surface of the 
water. Here they find the oxygen necessary for their devel- 
opment. If the eggs of Ctenolabrus with their great need 
for oxygen had a specific gravity large enough to cause them 
to sink to the bottom, they could scarcely develop in many 
places, since at the bottom of the ocean where processes of 
putrefaction are going on, the tension of oxygen is much 
less than at the surface. We may therefore expect, in gen- 
eral, that fish eggs which sink to the bottom of the ocean 
and develop there are much more independent of oxygen 
than the egg of Ctenolabrus. This is really often the case. 
The egg of Fundulus has a greater specific gravity than sea- 
water and develops at the bottom of the ocean. I have shown 
that the egg of Fundulus can develop for some time in the 
absence of oxygen. In these experiments the eggs were 
introduced with a few drops of sea-water into a small glass 
tube sealed at its lower end, and this tube was put into a 
test-tube containing several cubic centimeters of an alkaline 
pyrogallol solution. The test-tube then was sealed at the 
top. The pyrogallol solution was prepared according to 
Hempel’s directions, and the oxygen must have been ab- 
sorbed in a short time. Nevertheless, the eggs not only 
segmented, but they developed as far as normal eggs do in 
about fifteen hours after fertilization. A large blastoderm 
was formed which spread over a great part of the surface 
of the egg. 
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