60 THE PHYSICAL BASIS OF INHERITANCE 



combination of the paternal and maternal chromosomes to 

 form one nucleus the segmentation-nucleus. Moreover, the 

 maternal and paternal contributions are, as we have noted, 

 distributed with scrupulous equality, certainly to the first 

 two cells of the embryo, and probably to all later-formed 

 cells. 



" The latter conclusion, which long remained a mere surmise, 

 has been rendered nearly a certainty by the remarkable ob- 

 servations of Riickert, Zoja, and Haecker. We must, therefore, 

 accept the high probability of the conclusion that the specific 

 character of the cell is in the last analysis determined by that 

 of the nucleus that is, by the chromatin ; and that in the 

 equal distribution of paternal and maternal chromatin to all 

 the cells of the offspring, we find the physiological explanation of 



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