HEREDITY. 21 



very Kmited, that to study a gene, we must first happen to find 

 individucds lacking it for comparison, and that for this reason 

 only those genes which are not indispensable for an approxi- 

 mately normal life of the individual can ever be well studied. 



We saw, that evidence is accumul?iting, showing that every 

 somatic cell of a plant or animal has the genotype, the set of 

 genes present in the original zygote. We have the evidence of 

 regeneration in plants and animals and the fact, that in some 

 plants it is possible to grow a complete plant like the mother- 

 plant from one epidermis-cell. But, at the same time, we know 

 that individual properties of different cells differ amazingly, 

 morphologically as well as chemically. We would, to account 

 for these facts, incline toward a belief that inside the nucleus 

 a complete set of genes is somehow kept intact, whereas the 

 cytoplasm of the different ceUs of one individual may be very 

 different in different cells, to the point where one or two genes 

 may be quantitatively preponderant. This view is a modifica- 

 tion of de Vries' intracellular pangenesis with chemical sub- 

 stances substituted for vital pangenes. It is difficult to picture 

 the way, in which a special kind of cell takes over a special 

 function and prepares itself for that function so long as we 

 conceive the genes as vital units, "determining" the cell's qual- 

 ities. With the theory that the genes are autokatalitical sub- 

 stances, this differentiation becomes easier to understand. 



If we imagine, that a certain substance in the cells has some 

 importance for the metabolism of a plant, and that this sub- 

 stance has autokatalytic properties, in other words, that it is a 

 gene in this plant, we see how, wherever the constituents, the 

 ingredients, for the formation of this gene enter the cells, they 

 are assimilated and transformed into the combination, under 

 the influence of this substance^ the amoimt assimiliable propor- 

 tionate to the amount of the gene present in the cytoplasm. It 

 is evident, that after assimilating a quantity of the materials 

 into this substance A, this cell or its daughter-cells become 

 able to assimilate very much more of the same materials into A 

 under the influence of a very much greater quantity of A. It is 



