102 THE CELL IN RELATION TO 



[Substance. I doubt whether any one holds the 

 view, which some of the opponents of the chro- 

 matin hypothesis have endeavored to force upon 

 its adherents, that the nucleus enjoys a complete 

 " monopoly of heredity." To what extent the 

 chromatin embodies primary factors of deter- 

 mination remains to be shown by further re- 

 search. We are stiU too ignorant of the physio- 

 logical relations of the nucleus and cytoplasm to 

 be justified in any attitude of dogmatism on this 

 question. But as a matter of evidence the con- 

 clusion that chromatin does embody such factors 

 seems at least a probable one. As a means of 

 practical inquiry it is, I believe, a good working 

 hypothesis, without which we should be deprived 

 of one of our most effective instruments for the 

 analysis of the mechanism of heredity. And re- 

 cent research has, I think, clearly shown that, far 

 from being exhausted as some of its critics would 

 have us beheve, this hypothesis is steadily open- 

 ing new possibihties of inqmry. 



CELL-DIVISION 



Accepting the idioplasm hypothesis, in the 

 sense I have indicated, what do we know of its 

 mode of transmission? We may answer with 

 assurance that it is transmitted from cell to cell 

 by division; and we may still safely assume, I 

 think, in most cases by mitotic or karyokinetic 

 division, though the direct or amitotic process may 

 play a larger role than was formerly supposed. 



