L'NFERTILIZED STARFISH EGGS. 30! 



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 no oxygen. It is self-evident that the eggs must be intro- 

 duced 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 l 

 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 con- 

 ditions 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 maturated in a few hours and were, in less than 

 twelve hours, opaque and dead, while the water was still abso- 

 lutely clear and without odor of putrefaction. After twenty-four 

 hours the water became putrid and contained many bacteria. 

 Even after three days, when the water was exceedingly foul and 

 cloudy, a portion of the eggs which had lain in a heap, that is to 

 say, without oxygen, were immature and living. They were 

 introduced into fresh water and spread out into a thin layer. 

 They maturated and developed into swimming larvse upon the 

 addition of sperm. It is self evident of course that even immature 

 eggs finally become the prey of bacteria, and so go to pieces in 

 the sea water. 



The same experiment can be made in a somewhat more compli- 

 cated way with pure oxygen and hydrogen. The freshly laid eggs 



