EFFECT OF RADIUM ON FERTILIZATION 89 



former found that the fertihzed egg of Ascaris megalocephala, 

 after exposure to radium, shows much the same type of abnor- 

 maUty that had been observed by others, namely, that the chro- 

 matin alone is affected, being broken up into numerous irregu- 

 lar granules. In division these granules are not exactly equall}^ 

 divided, but part go to one blastomere and part to the other. The 

 astral system and the plasma are not affected at all. Miss Hert- 

 wig concludes that the effect of the radium radiations is a direct 

 one on the chromatin, and not indirect, as Schwartz and Schaper 

 claimed. 



G. Hertwig ('12) has studied the effect of fertilizing the normal 

 sea urchin egg with radiated sperm. The sperm remains active 

 after twelve hours of intense radiation. But such sperm, even 

 though motile and able to penetrate the egg, is incapable, in 

 many instances, of fusing with the egg nucleus. Inside the egg 

 it remains as a compact mass near the latter which divides, being 

 provided with centrosomes derived from the sperm. In some 

 instances it may become involved as a foreign body in the spindle 

 of the dividing egg nucleus, in which case it causes abnormalities 

 in the distribution and form of the egg chromosomes. In divi- 

 sion it usually goes to one blastomere, and in later divisions may 

 operate to produce very abnormal mitoses resulting in an abnormal 

 larva. In other instances it may fuse with the egg nucleus but 

 even then it behaves abnormally and is eliminated during the 

 subsequent divisions. The main point is that the embryos aris- 

 ing from this treatment are parthenogenetic. Thus cytological 

 study has confirmed his earlier hypothesis based on the experi- 

 ments with the frog's egg. 



Since there is no visible evidence that the protoplasm of the 

 sperm or fertilized egg has been injured, the Hertwigs conclude 

 that only the chromatin is affected. This conclusion is supported 

 by the fact that the harmful effect of the radiations is much great- 

 er in the fertilized egg, with twice as much chromatin, than in the 

 normal egg fertilized by radiated sperm. 



Two hypotheses have been advanced to explain the phenomena 

 that have been described. The first, proposed by Schwarz ('04) was 

 based on the fact that egg yolk is decomposed by exposure to the 



