NATURAL DEATH AND FERTILIZATION 731 



recognized. The sterilized flasks which were opened were 

 at all times free from foul odor, while the unsterilized flasks 

 gave off a penetrating stench, often after one, invariably 

 after two, days. The microscopic examination of the sea- 

 water for bacteria was always negative in the sterilized flasks, 

 always positive in the other flasks. In those flasks to which 

 2 c.c. of the putrid culture of starfish eggs had been added, 

 bacteria and infusoria were exceedingly numerous from the 

 beginning. 



Six hours after the beginning of the experiment one flask 

 of each of the three series was opened, and the eggs 

 examined microscopically. The picture was the same in all 

 three flasks. Nearly all the eggs were mature, and a small 

 number of them were opaque or black. But what is of the 

 greatest importance to us is the fact that the percentage of 

 opaque dead eggs was just as great in the sterile culture (if 

 not greater) than in the unsterilized or the infected sea- 

 water. 



Twelve hours later, that is to say eighteen hours after the 

 beginning of the experiment, one of the flasks of each of the 

 three cultures was again opened. At this time nearly all the 

 eggs of the sterile culture were opaque or black, and a few 

 were already granular. In the two other cultures an equal 

 percentage of the eggs were opaque. The eggs, therefore, 

 die just as rapidly in the sterilized flasks which are abso- 

 lutely free from bacteria as in the flasks containing bacteria. 

 Death follows from internal causes, and so rapidly that the 

 few bacteria in the sea-water are scarcely able to accelerate 

 the death of the eggs. The eggs have already died from 

 internal causes before the bacteria can attack them in suffi- 

 cient numbers to threaten their existence. 



The flasks which were opened later served only to corrob- 

 orate what has been said. The experiment was repeated 

 with the same result. Each of the flasks that were opened 



