NATURAL DEATH AND FERTILIZATION 737 
sea-water are introduced for ten or fifteen minutes into 100 
c.c. sea-water plus 4 c.c. 7%; HCl maturate very slowly or 
not at all when they are returned to normal sea-water. They 
also retain, as long as they are immature, the transparent, 
normal appearance of living eggs until they become the 
prey of bacteria. 
It seems to follow from these experiments that the same 
processes which underlie the maturation of starfish eggs 
also lead to their death (if they are not inhibited through 
circumstances which we designate by the term fertilization). 
I tried to see, now, whether it was also possible to maintain 
the life of the mature egg through lack of oxygen. I 
indeed obtained in a few cases positive results in this direc- 
tion. The eggs of a starfish were spread in a thin layer 
over the bottom of a dish. After three hours 75 per 
cent. of the eggs were maturated. A portion of the mature 
eggs was carefully introduced into the glass tube described 
above, in which the deeper layers suffered from lack of 
oxygen. A second portion was introduced into a small flask 
through which a steady stream of pure oxygen was passed. 
On the following morning, that is to say, fifteen hours after 
the eggs were brought into the atmosphere of pure oxygen, 
the various portions of the eggs were examined: The eggs 
introduced into the current of oxygen showed in one vessel 
98 per cent. mature and dark, dead eggs and 2 per cent. 
immature living eggs. The eggs which had remained in 
normal sea-water contained, as before, about 75 per cent. 
mature eggs, all of which, however, were black and dead, 
with the exception of a few eggs which had begun to divide,’ 
and were living. 
The immature eggs were also still living. Upon the other 
hand, the eggs which had been left in the glass tube in 
1This cleavage was possibly brought about through mechanical agitation; I 
had repeatedly shaken the dish to facilitate the introduction of oxygen into the 
sea-water. 
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