1 8 THE GERM-PLASM 



different pangenes in the entire organic world, because ' the 

 number of individual hereditary qualities required for the con- 

 struction of the latter is relatively small when compared with 

 the number of species ' ! Each species appears to us as an 

 extremely complicated structure : the whole organic world, how- 

 ever, seems to be the result of innumerable different combina- 

 tions and permutations oi relatively few factor's. 



The idea which is here so clearly and decidedly expressed of 

 the construction of innumerable species by various combinations 

 of relatively few pangenes, shows that, even from de Vries's point 

 of view, it is not the ' pangene niateriaV as such, which is the 

 main factor in determining the character of the species, but 

 rather its arrangeme?it, or as I shall afterwards express it, the 

 architectjire of the gerni-plasjii. 



De Vries certainly speaks frequently of ' groups of pangenes,' 

 but he only just touches upon this idea, and postpones entering 

 into details until further discoveries are made with regard to the 

 mechanism of nuclear division. Important as his fundamental 

 view as regards the composition of the germ substance out of 

 primary constituents undoubtedly is, it may easily seem to ex- 

 plain more than it really does ; without assuming the formation 

 of groups of such primary constituents for a number of orders 

 each included in the other, even the simplest case of ontogeny 

 cannot be explained, quite apart from reversion or any other 

 complicated phenomenon of amphigonic heredity. Darwin's 

 theory of pangenesis accomplishes more in this respect than 

 does de Vries's modification of it, inasmuch as the former at 

 least deals with the primary constituents of <:^//-sti"uctures. The 

 mere presence of a certain collection of pangenes in the germ 

 does not necessitate the formation in the offspring of similar 

 cells to those which existed in the parent ; for the character of 

 the individual cell is determined by a definite selection of pan- 

 genes. If, indeed, it be assumed that the required pangenes 

 always lie close together, and are always ready at hand when- 

 ever they are wanted, an explanation of any particular phenom- 

 enon of heredity is no longer difficult, but it seems to me that 

 it would then be necessary to show how the nature of the germ 

 can determine that the right primary constituents are always at 

 the right spot. 



As already stated, de Vries occasionally speaks of groups of 

 pangenes, but, at the same time, he looks upon the view of 



