284 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
present in the sea-water are scarcely able to accelerate the 
death of the eggs. The eggs have indeed already died from 
intrinsic factors before the bacteria can enter. 
The flasks opened later only confirmed the above. Each 
one opened in the first few days contained also a small number 
of living eggs of clear-cut appearance. The latter were, how- 
ever, without exception, unripe. The experiment therefore 
proved that the ripe eggs of the starfish decay in a few hours, 
and the causes of their death must not be looked for in the 
bacteria of the sea-water; and, further, that under the same 
conditions the unripe eggs remain alive. 
An experiment was now made to find out whether the life 
of the unripe eggs can be prolonged by preventing them from 
ripening. As previously mentioned, maturation requires the 
presence of free oxygen. Freshly laid eggs of Asterias were 
divided into two series of eight flasks. One series of flasks was 
connected with a hydrogen generator, the other with a cylinder 
containing pure oxygen. Before the beginning of the experiment, 
all the air in the one series of flasks was driven out by a stream 
of hydrogen, and a vigorous stream of hydrogen was maintained 
throughout the experiment. Both series of flasks contained 
freshly gathered unripe eggs of Asterias. The experiment 
continued for three days, and from time to time one flask was 
disconnected and its contents examined. The eggs which were 
exposed to the stream of oxygen matured as quickly and in as 
large numbers as in normal sea-water, and the ripe eggs died 
as soon. In the stream of hydrogen, maturation did not take 
place in the majority of the eggs and they remained alive. A 
vigorous development of bacteria took place in the hydrogen 
culture while there was none or only a weak one in the oxygen 
culture. 
The death and disintegration of the eggs is also prevented 
by treatment with acid, which, as previously mentioned, pre- 
vents the maturation of the eggs (without killing them). Eggs 
