EFFECT OF RADIUM ON FERTILIZATION 119 



nucleo-proteids at a normal rate. Hence it is either eliminated, 

 as Hertwig has shown, or remains stationary, after developing up 

 to a certain point. In like manner, the egg nucleus, after the 

 egg has been radiated, fails to develop. That the normal sperm 

 which fertilizes such an egg may develop, as suggested by Hertwig, 

 indicates that the egg protoplasm, made up of ''simple" proteins, 

 has not been greatly changed. In Nereis evidently such proteins 

 have been affected, as shown by the abnormal behavior of the 

 sperm nucleus. When the fertilized eggs are radiated, the radia- 

 tion is applied at a period when the synthetic process in the 

 formation of the chromosomes is most active. Hence, any 

 acceleration of the autolytic enzymes results in a speedy deterior- 

 ation of the chromatin. The latent period which is found in 

 many instances when the radiation is neither prolonged or in- 

 intense may be explained by this hypothesis. Only a slight 

 acceleration is brought about by the treatment, but the effect 

 of autolysis is cumulative, and becomes manifest after a period, 

 depending on the rate of acceleration. The nuclear material has 

 been broken down to such an extent that, after division, the 

 chromosomes cannot be built up again. In this connection it 

 might be suggested that the normal nuclear division takes place 

 when the ratio between the amount of nucleoprotein and simple 

 proteins of the protoplasm has reached a certain limit. After 

 the division the ratio is changed and constructive action again 

 takes place. 



SUMMARY AND CONCLUSION 



1. Radiated spermatozoa of Nereis react in two ways to the 

 normal egg. They may normally stimulate it, and be drawn in, 

 but subsequently fail to develop, or they may fail to stimulate 

 the egg sufficiently and so remain external. In the first case, the 

 sperm nucleus and aster may fail to develop and to fuse with the 

 egg nucleus. In the second case, the egg nucleus develops with- 

 out an aster. 



2. The radiated egg at the time of fertilization may or may not 

 extrude the cortical layer. In either case, the maturation phe- 

 nomena are more or less abnormal. The germ nuclei develop 



