EFFEICT OF RADIUM ON FERTILIZATION 115 



not fully attained. The failufe of the cortical layer to be given 

 off may be due to a change in the plasma membrane, or to a 

 change in the colloids of that layer. The possibility of such a 

 change will be discussed later. 



The formation of the polar bodies has been shown to be ab- 

 normal both in respect to the chromatic and achromatic elements 

 of the spindle. It might be concluded from this that both parts 

 were equally affected by the radium radiations but this is not 

 necessarily true, for it has been shown that the presence of the 

 cortical layer has an inhibiting effect on mitotic phenomena. 

 This suggestion has been made by Bataillon who holds that in 

 the cortical layer are certain katabolic products of metabolism 

 which hold the egg in check until they are given off. The in- 

 creased permeability at the time of fertilization allows them to 

 be extruded. The resulting egg membrane is therefore a result 

 of such an action and is incidental, indicating merelj'' that certain 

 more fundamantal phenomena have been taking place. In 

 Nereis, when the cortical layer persists, the maturation divisions 

 are always abnormal, remaining permanently in the interior of 

 the egg or else showing other defects which have been described 

 above. If, however, the cortical layer is extruded in part, the 

 spindle migrates to that region and the figure is normal. It 

 should be mentioned, however, that occasionally in eggs from 

 which the cortical layer has been extruded, the same type of ab- 

 normalities may be found. The radium radiations therefore, 

 have affected not only the surface layer, but also the deeper 

 lying protoplasm. 



That the abnormalities in the chromatin appear during the 

 formation of the chromosomes, when they are being built up 

 from the protoplasmic constituents indicates that the latter 

 themselves may have been modified, or that the agents through 

 which they are so built are affected, as well as the chromatin 

 itself. These abnormalities are even more strikingly manifested 

 in the' division of the fertilized egg, as described above, and 

 also by P. Hertwig. 



If we attempt to explain the phenomena already described by 

 the hypotheses of Schwarz or of Hertwig we are at once involved 



