The Mutation Hypothesis. 69 



characters that have ah-eady arisen but it cannot of itself 

 produce new forms. 



This author then proceeds to a comparison of the 

 fundamental principles of the selection and mutation the- 

 ory. As a result, he finds that the theory that species 

 have originated by the selection of individual differences 

 is beset with series difficulties, whereas the belief that 

 this has taken place by mutations (heterogenetic varia- 

 tions) provides us with a satisfactory explanation or at 

 any rate is in close accord with the facts. Two facts that 

 strongly favor this view are (1) the absence of transi- 

 tional forms and (2) the existence of at least apparently 

 useless characters. 



Darwin's view is that the probability of a progressive 

 development in animals and plants is great in proportion 

 to the severity of the struggle for existence. Kor- 

 SCHINSKY on the other hand holds that favorable con- 

 ditions afford the best opportunity for the appearance 

 of mutations. For the new forms in order to establish 

 themselves require suitable opportunity for the develop- 

 ment of their powers and fertility to the full. It will 

 be seen that this contrasts strongly with Darwin's view, 

 which is that the innumerable weaker variants simply 

 cease to exist while the rarer stronger ones survive. 



I shall now close this historical sketch. I hope, at a 

 later date to review more fully the views of modern 

 authors; it will then be seen that the general opinion is 

 that the theory of selection is unsatisfactory. For exam- 

 ple DuNCKER says that individual variability is static 

 rather than kinetic; and therefore does not provide 

 material for natural selection.^ Lord Salisbury said 

 in his presidential address at the meeting of the British 



^ Biolog. Centralhlatt, 1899, p. 2,72- 



