THE GERM-PLASM 47 



the cell is controlled by the nucleus. It, moreover, fits in very 

 well with my other views. 



As long as I was engaged in seeking for an epigenetic theory 

 of heredity, an explanation of this sort was naturally impossible, 

 but as soon as I assumed that the germ-plasm consisted of 

 biophors, the various kinds of which are required for the various 

 characters of the respective cells, it was not only possible to 

 suppose that the particles exerted an influence of this nature on 

 the cell, but such an explanation of the phenomena became the 

 most natural and satisfactory one. Much may of course be 

 urged against this fundamental assumption, and it is not in 

 itself a sufficient explanation ; but it is not only fruitless to 

 attempt a satisfactory explanation from the other point of view, 

 but as will appear later on, de Vries's conception alone agrees 

 with certain fundamental biological principles. 



If the nuclear substance exerted an emitted influence on the 

 cell-body so as to give rise to the structures characteristic of this 

 particular kind of cell, they would be formed by a kind of 

 '• generatio egiiivoca ' ; they would have arisen by the operation 

 of an external influence on the given substance in the cell, just 

 as would be the case in primordial generation. Particularly 

 favourable influences would have operated on certain combina- 

 tions of inorganic substances in such a way as to give rise to a 

 vital particle. 



We know nothing of such a primordial generation as far as 

 our experience extends, and even if it must be considered to be 

 logically necessary, we have every reason to suppose that it has 

 no share in the origin of those forms of life with which we are 

 acquainted, but that these always arise by division from others 

 similar to themselves. Moreover, what is true of the independ- 

 ent organisms familiar to us must also hold good for all the 

 different orders of vital units which have united to form higher 

 organisms, for each of the earliest and lowest organisms must 

 have been neither more nor less than the eqidvaletU of one 

 biophor. If, then, in order to explain the presence of life on 

 the earth, we must assume that such individual biophors arose 

 at one time by primordial generation, they must have been 

 capable of reproduction by division immediately after their 

 origin, for such multiplication is caused directly by the pri- 

 mary forces of life, — assimilation and growth. We can only 

 imagine the very simplest biophors as having been produced 



