116 CHARLES PACKARD 



in difficulties. The latter involves a number of difficult assump- 

 tions. First, when the sperm is radiated, the poison generated 

 in the nucleus must remain altogether in that structure, since the 

 protoplasmic activity concerned in movement is not affected, or 

 else it must be assumed that the poison is specific for the chro- 

 matin itself, not affecting the protoplasm. And secondly, it must 

 exert no influence on the egg protoplasm during division, since a 

 normal haploid division can occur provided the sperm head does 

 not mechanically interfere in the spindle. If the sperm head fuses 

 with the nucleus its poison exerts no influence on the egg chrom- 

 atin, other than to cause it to eliminate the sperm chromatin. 

 But it has been shown that in Nereis the protoplasm of the sperm 

 has evidently been changed. Hence it would be necessary to 

 postulate that the poison had extended into the protoplasm and 

 had affected the sperm centrosome — a condition contrary to the 

 first supposition. In the egg it is very evident that the proto- 

 plasm has been affected. Hence the hypothesis that poison is 

 generated solely in the nucleus is not tenable. A modification 

 of the poison theory will, I believe, explain more of the facts, and 

 such a modification will be discussed later. 



The lecithin hypothesis is hardly as satisfactory as the other. 

 The fact that the sperm nucleus is undoubtedly affected by the 

 radiations makes it evident that they are not specific for the 

 lecithin in the protoplasm. The behavior of the radiated egg 

 is more easily explained for it has been shown that the cortical 

 layer, which contains considerable lecithin is affected. If that 

 substance which is distributed throughout the egg is utilized in 

 the upbuilding of the chromatin, the phenomenon could be 

 explained. 



These two hypotheses, therefore, fail at certain points when 

 they are used to explain the facts observed in the fertilization of 

 the egg of Nereis. I believe that I have given good evidence that 

 both hypotheses may be true in part, since both protoplasm and 

 chromatin are affected by the radium radiations. The question 

 now arises as to the means by which such changes can be brought 

 about. 



