56 THE GERM-PLASM 



all the hundred characters would vary at the same time. The 

 capacity for transmission and that of independent variation from 

 the germ onwards are distinct from one another. 



The germ-plasm must consequently be composed of as many 

 units as there are transmissible parts in the body which are in- 

 dependently variable from the germ onwards. Each of these 

 units cannot be smaller than a biophor, and they can therefore 

 not be simple molecules within a biophor ; for variation is a 

 biological conception, and a biological element does not pre- 

 suppose a one that is merely physical. 



What parts of the body of a multicellular organism are repre- 

 sented in the germ by special particles of the minimum value of 

 one biophor? Is each cell, or even each part of a cell? Darwin 

 adopted the former, and de Vries the latter of these two alter- 

 natives. Darwin's gemmules are germs of cells, so that every 

 cell of the body would be represented in the ovum by these 

 units ; while de Vries's pangenes are in a sense germs of the 

 characters or structures (' Zellorganen ') of the cell. There is 

 no doubt that the hereditary variations in plants and animals 

 manifest themselves in alterations of the individual parts or 

 structures of the cell, and not only in the 7iu))iber, relative 

 arrangement, and the changes in the form, size, and nature 

 of the cells as a whole. The variegated varieties of our orna- 

 mental plants possess similar cells to those of their ancestral 

 forms, but the green colour of the leaf is absent in certain 

 of the cells : the red tint of the leaves of the copper beech, 

 and other varieties of plants, depends on the red colour of the 

 sap in a certain layer of cells, and this colour is transmissible. 

 The coloured pattern on a butterfly's wing or a bird's plumage 

 depends on cellular elements which were probably all alike 

 in remote ancestors, but which afterwards became gradually 

 changed by hereditary variations in the individual components 

 or in the structure of the cell. Although the entire phyletic 

 transformation of a species does not by any means alone depend 

 on its ////r^-cellular variation, the latter has, nevertheless, con- 

 stantly accompanied the other variations, and has shared to 

 a greater or less extent in the transformation of the species. 

 Hence it cannot be doubted that even in multicellular forms 

 not only the cells as a whole, but also their parts, are determined 

 from the germ onwards. 



It seems therefore impossible to avoid the stupendous as- 



