NATURAL DEATH AND FERTILIZATION 735 



eggs live longer. We begin with the experiment which is 

 technically most simple. The eggs streaming from the 

 ovary are divided into two portions. One portion of eggs 

 is carefully distributed without mechanical agitation, by 

 carefully tipping the vessel, in a thin layer over the bottom 

 of the vessel. The vessel must be low and the layer of sea- 

 water covering the eggs not too deep, so that the diffusion 

 of oxygen to the eggs can occur with ease. A second portion 

 is introduced with just as great care into a small-calibered 

 glass tube sealed at one end. This glass tube is half filled 

 with eggs so that one is certain that the lower layers of the 

 eggs in the pipette receive little or 110 oxygen. It is self- 

 evident that the eggs must be introduced into the tube 

 immediately after being laid. When, after twenty-four 

 hours, the eggs which are distributed over the bottom of the 

 glass dish and which receive a large amount of oxygen are 

 compared with those at the bottom of the glass tube, a 

 striking difference is found between them. The eggs richly 

 supplied with oxygen contain a much larger percentage of 

 mature dead and black eggs than those kept in the lack of 

 oxygen. In the latter the living immature eggs are in the 

 majority, and a part of these maturate when spread out in a 

 thin layer over the bottom of a vessel. These experiments 

 are also well adapted to show that the rapid death of the 

 mature unfertilized sea-urchin eggs is determined through 

 internal conditions and not by the bacteria contained in the 

 sea-water. I will cite an example. 



One portion of a lot of eggs was spread out in a thin 

 layer over the bottom of a dish; another was heaped in a 

 mass in the same dish. The sea- water was the same in both 

 cases. The first portion of eggs matured in a few hours and 

 were, in less than twelve hours, opaque and dead, while the 

 water was still absolutely clear and without odor of putrefac- 

 tion. After twenty -four hours the water became putrid and 



