74 Hypothetical Bearers of Hereditary Characters 



some that have long been inactive may resume activity, 

 and finally the grouping of the individual pangens may 

 possibly change. All of these processes will amply ex- 

 plain a strongly fluctuating variability. 



In the second place some pangens may change their 

 nature more or less in their successive divisions or, in 

 other words, new kinds of pangens may develop from 

 those already existing. And when the new pangens, per- 

 haps in the course of several generations, gradually in- 

 crease to such an extent that they can become active, new 

 characters must manifest themselves in the organism. 



In a word : An altered numerical relation of the pan- 

 gens already present, and the formation of new kinds of 

 pangens must form the two main factors of variability.*^ 

 Unfortunately we have not yet succeeded in analyzing 

 the observed variations so far as to be able to determine 

 the share of each of those factors. But it is clear that 

 the former kind is more likely to determine the individual 

 differences and the numberless small, aFmost daily varia- 

 tions and monstrosities, while the second one has chiefly 

 to produce those variations on which depends the grad- 

 ually increasing differentiation of the entire animal and 

 vegetable world. 



This conception of phylogenetic variability indicates 

 that the pangens, too, must have their pedigrees which 

 correspond to the pedigrees of the respective character- 

 istics. At every advance in the pedigree of the species 

 one or more new kinds of pangens must have developed 

 from those present. In the lowest organisms, therefore, 

 the pangens themselves become relatively simple, and not 



*sin a note to the translator, the author says : "That sentence 

 has since become the basis of the experiments described in my 'Mu- 

 tationstheorie.' " Tr. 



