ioi8 LIFE : OUTLINES OF GENERAL BIOLOGY 



Mendelian fashion, often going one better than the parents, and 

 occurring copiously even in "pure lines", that is to say, in lineages 

 all descended from one. As to the wild species of snapdragon, Baur 

 has come to the conclusion that they have been and are in many 

 cases the result of the summation of small mutations comparable 

 to those that are of everyday occurrence in the garden. In natural 

 conditions, he says, the summation may be put to the credit of 

 Natural Selection, which sifted and sifts the mutations in reference 

 to the diverse and changeful conditions of locality and climate. 

 Large mutations he recognises as also occurring in cultivated races 



Fig. 177. 



Two Mutants (A and B) of the Evening Primrose {CEnothera lamarckiana). 



After De Vries, 



of snapdragon, and on these, apt to be extreme, the gardener 

 operates in his Artificial Selection. His sieve is large enough, so to 

 speak, to let pass some mutations which Natural Selection might 

 sift away. So we substantially come back to Darwin's own Dar- 

 winism! 



Since Darwin's day the effective operation of Natural Selection 

 has been repeatedly demonstrated, e.g. by Weldon, Crampton, 

 Poulton, and Cesnola. Why, then, has there been this reaction from 

 the theory? Largely because so few think resolutely, or are able to 

 withstand being blown about by every wind of doctrine. Let us 

 consider briefly the three most important objections that have been 

 brought against Darwin's view. 



(i).If mutations have been common throughout the evolution- 



