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 



