58 PHYLOGENY 



In my opinion, competition simply removes what is less capable of existence, 

 but it is wholly without influence in bringing to pass anything more perfect or 

 better adapted." Theorie der Abstammungslehre, p. 285. 



" The fortuitous or directionless variation of individuals would be conceivable, 

 if it were conditioned by external influences (food, temperature, light, elec- 

 tricity, gravitation); for, as these causes obviously cannot be brought into any 

 definite relation to the more or less complex organization, they must effect 

 sometimes a positive, sometimes a negative, step. If, however, the causes of 

 variation are internal, in the constitution of the substance, then the matter 

 stands otherwise. In this case the determinate organization of the substance 

 must exercise a restricting influence upon its own variation ; and this influence, 

 as development begins at the lowest point, can only take effect in an upward 

 direction." Abstammungslehre, p. 12. 



" Individuals transmit to their offspring the tendency to be like themselves, 

 but the offspring are not perfectly like the parents. The tendency to variation 

 must therefore also be transmitted. A primordium, if all conditions are favorable, 

 must be able to develop ever farther in a series of generations, as a capital 

 enlarges to which interest is added annually; for each generation inherits from 

 the preceding not only the possibility to realize the capital, but also the possi- 

 bility to add the interest." Individuality in Nature, 1856. 



Hugo de Vries. 



"According to the theory of mutation, species have not arisen through 

 gradual selection continued for hundreds or thousands of years, but by steps, 

 through sudden though small transmutations. In contrast with variations, 

 which are changes advancing in a linear direction, the transformations to be 

 called mutations diverge in new directions. They take place, then, so far as 

 experience goes, without definite direction, i. e., in various directions." Die 

 Mutationstheorie, vol. I, p. 150. 



