1915] Influence of Radium Rays 153 



Why, after passing a certain point, does increased radia- 

 tion result in improvement in development ? This is explained 

 on the assumption that the degree of abnormality depends 

 not only on the degree of injury to the chromatin but also 

 upon its power to increase and divide so that all cells will be 

 alfected by the radium sick chromatin. After passing a 

 certain point the power of the paternal chromatin to increase 

 and divide becomes less or becomes wholly lacking. If the 

 chromatin loses its power to increase after prolonged radia- 

 tion then a real fertilization in the sense of a fusion of equal 

 maternal and paternal germs no longer occurs, and the de- 

 velopment of the egg, assumes the character of parthenogensis. 

 Fertilization, where the power of the chromatin to increase 

 is wholly lost, is only a developmental stimulus. 



That the eggs of vertebrates generally may have the 

 power to develop parthenogenetically seems to be shown by 

 Bataillon's experiments on the frog eggs and by Lacaillon's 

 discovery that bird eggs sometimes start development natur- 

 ally without having been fertilized. Bataillon caused frog 

 eggs to develop without fertilization by pricking them with 

 a fine platinum needle. His experiments have been repeated 

 by Dr. Bancroft, of the Rockefeller Institute, in our own 

 laboratory, and also by MacClendon of this country, by 

 Dehorne and Henneguy of France, by Brachet and Ilerlant 

 of Belgium, and by Levy of Germany. And so it is now a 

 well established fact that the frog egg has the power to 

 develop parthenogenetically. From some of the later inves- 

 tigations, however, it now appears that for the frog egg to 

 develop beyond the very first stages, something more than a 

 puncture is necessary. A blood or lymph cell, or at any rate 

 some solid element derived from the blood or lymph, must 

 be introduced into the egg cytoplasm. This calls to mind 

 that an American, Guyer, before Bataillon's discovery, re- 

 ported that he had succeeded in fertilizing frog eggs with 

 blood and lymph. Guyer in interpreting his results, seems 

 just to have missed the real fact that the egg itself under the 

 influence of a stimulating agency starts to develop. 



