THE PHENOMEXA OF REVERSION 351 



I know of no instance in which there is such a wide difference 

 as regards the activity of the idioplasm in successive cell- 

 generations as is the case in the germ-mother-cells and the 

 mature germ-cells arising from them. If, however, even in this 

 very striking instance of a sudden change of function of the 

 idioplasm, the idioplasm which was active at first is not removed 

 from the cell, such a process cannot occur in any other case ; 

 and we are consequently justified in applying to all other cells 

 the conclusion derived from the behaviour of the germ-cells, 

 and in considering it as proved that the active idioplasm of a 

 cell becomes used up in consequence of its activity. 



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