1 6 thf: germ-plasm 



'free miscibility of the qualities.* He contests as superfluous 

 the assumption of higher units, such as might be formed by a 

 certain number of pangenes in a definite order ; and this view 

 seems to me to be the weak point in his argument. 



In the section on the control of the cell by the nuclear sub- 

 stance, I shall adopt what seems to me to be a remarkably happy 

 idea on the part of de Vries, who supposes that material parti- 

 cles leave the nucleus, and take part in the construction of the 

 body of the cell. These particles correspond to the ' pangenes,' 

 they are the 'bearers of the qualities' of the cell, the specific 

 character of which I believe to be stamped upon it by the 

 nature, the different varieties, and the proportional numbers of 

 these particles. 



But does the character of a species depend only on these 

 primary qualities of the cell? Are there not qualities of various 

 degrees — primary, secondary, and so on? The pangenes are 

 primary ' bearers of qualities ' ; their mere presence in the heredi- 

 tary substance gives no indication, or at most, only a very slight 

 one, as to the character of a species. If, for instance, ' chlorophyll- 

 pangenes ' are present in the egg-cell of a plant, the only conclu- 

 sions we can draw as to the specific character of the latter are 

 that it will have green cells of some sort : but we cannot thereby 

 determine where they will be situated, or which portions of the 

 plant will be green, and which variegated ; or again, whether its 

 flowers will be green, white, or of some other colour. Not until 

 we were able to find groups of pangenes in the germ-substance, 

 some of which were destined to give rise to leaves, and others 

 to flowers, should we be able to say whether the latter will be 

 green or otherwise. 



In the course of his remarks, de Vries mentions the stripes of 

 a zebra. How can these be hereditary if the different kinds of 

 pangenes merely lie close together in the germ without being 

 united into fixed groups, hereditary as such / There can be no 

 ' zebra pangenes,' because the striping of a zebra is not a cell- 

 character. There may perhaps be black and white pangenes 

 whose presence causes the black or white colour of a cell : but 

 the striping of a zebra does not depend on the development of 

 these colours within a cell, but is due to the regular alternation 

 of thousands of black and white cells arranged in stripes. 



De Vries, in another place, refers to the long-stalked variety 

 of the alpine Primula acaulis, which is due to reversion to a 



