84 



Scientific Proceedings (32). 



this injury is rather slight, and these eggs are able to develop into 

 larvae without any further treatment. In the egg of the Cahfor- 

 nian sea-urchin this secondary, injurious effect connected with the 

 artificial membrane formation is more severe and demands a further 

 treatment of the egg. This consists in preventing the eggs from 

 developing for about from two to three hours after the membrane 

 formation, by depriving them of oxygen or by preventing oxida- 

 tions in the egg through the addition of a trace of potassium cyan- 

 ide. During this time the egg is able to recuperate from the in- 

 jurious effects of the membrane formation and is able to develop 

 perfectly normally into a pluteus if transferred into normal sea- 

 water. In my first experiments with this method, four years ago. 

 not more than ten per cent, of the eggs could be caused to develop 

 in this way. I have recently found that by a slight improvement 

 of the method all the eggs can be caused to develop into larvae, 

 The segmentation is as a rule as normal as if the eggs were fer- 

 tilized by sperm. A second method of overcoming the injurious 

 effect caused by the artificial membrane formation consists in put- 

 ting the eggs for from 10 to 40 minutes into hypertonic sea-water. 

 This method also causes all the eggs to develop. 



These experiments showed that the process of membrane for- 

 mation is the real cause which starts the development of the unferti- 

 lized egg ; and the question therefore arose what the nature of 

 this process is. My recent experiments have shown that the 

 agencies which cause hemolysis also cause the membrane for- 

 mation and the development of the unfertilized egg. I have thus 

 been able to show that saponin, solanin, digitalin, bile salts, fatty 

 acids, alkalis, hydrocarbons, ether and alcohols and the blood 

 serum of not too closely related forms cause the membrane forma- 

 tion of the unfertilized egg and its subsequent development. 

 There remained only one cytolytic substance which seemed to 

 form an exception, namely, soap, but experiments which I have 

 recently carried out have shown that it is possible to cause the 

 membrane formation and subsequent development of the egg with 

 sodium oleate. 



If the unfertilized eggs of the sea-urchin are put into a mixture 

 of 50 c.c. N/2 sodium chloride -f 0.2 c.c. N/io sodium oleate, 

 the eggs form no membrane, nor do they undergo cytolysis ; but 



