ACTIVE AND PASSIVE DETERMINANTS 33 



difEerentiated destiny in the process of development. The 

 blastomeres which develop the endodermic system must neces- 

 sarily have a difierent prospective value from the blastomeres 

 which develop the ectoderm. 



We must also suppose that the determinants exist in two 

 states — active and passive. These states are to be understood 

 as relating to the mode of action which a determinant may exert 

 on the cell in which it lies. During the period in which they are 

 in a passive state the determinants increase by growth, but do 

 not influence the development of the cell. They may, indeed, 

 for instance, remain so passive that they never express them- 

 selves except in pecuhar and unusual conditions, constituting a 

 reserve of determinants which become active in regenerating a 

 lost part. 



It may be asked, then, if the determinants are pre-adapted to 

 the particular cells which they are to determine ? Whether the 

 biophors which compose them are, for instance, muscle biophors 

 or gland biophors ? Whether the plant derives its capacity of 

 producing chlorophyll from chlorophyll biophors ? It is evident 

 that the biophors, which have the power of transforming an un- 

 differentiated embryonic cell into a highly differentiated tissue- 

 cell, must possess a specific nature of infinite complexity ; but it 

 should be noted that it is not the biophor alone which is capable 

 of producing a muscle-ceU or a gland-cell : it is rather the biophor, 

 in conjunction with the given elements of the cell, which pro- 

 duces the differentiated ceU, with its muscle substance or gland 

 substance or chlorophyll substance. But the biophor, which is 

 the vehicle of the capacity of forming a muscle-cell or a chloro- 

 phyll ceU identical to the muscle-cell or to the chlorophyll cell 

 of the preceding generation, must certainly possess a specific 

 and weU-defined structure which differentiates it from the other 

 biophors, and enables it to secure the continuity of the particular 

 quality which it bears. 



In connection with the liberation of the determinants, we must 



3 



