288 MORPHOLOGY 



are inconstant. If a plant which has been built up in certain characters 

 by culture be left to nature, it reverts or " runs back," and its descend- 

 ants soon lose the characters of cultivation and resume those of the 

 ancestral stock. It is evident that the establishment of a new species 

 demands constancy in the built-up characters. The only answer to this 

 objection is that the characters for which man selects are not those for 

 which nature selects; and therefore the inconstancy in nature of a plant 

 built up by culture is no proof that a plant built up by natural selec- 

 tion would be inconstant in nature. 



(4) It is also urged that many forms and organs continue to exist 

 which are in no sense " adapted." If nature is selecting suitable indi- 

 viduals and organs, that is, those " adapted " to their environment, and 

 is destroying those that are not, why do so many of the latter sur- 

 vive? There are so many cases of this kind, that the selection by nature 

 does not seem to be based upon the suitability of an individual or an organ. 



(5) Perhaps the most serious objection to the theory is that it de- 

 mands a selection among such slight variations that one can hardly 

 be conceived of as having any decided advantage over another, really 

 a " life and death advantage." If broad leaves are of advantage to a 

 certain species growing under certain conditions, selection among indi- 

 viduals with broad and narrow leaves would seem to be easy; but the 

 theory demands that the selection be made before the broad leaves are 

 built up, and continue during the slow process of building. In other 

 words, the advantage given by a completed structure is not evident dur- 

 ing the process of building up; but natural selection is supposed to be 

 directing this building up on the basis of a distinct advantage from 

 generation to generation. To select among completely equipped indi- 

 viduals is one thing ; but to select so that individuals may become 

 equipped is a very different thing. 



Mutation. — In 1901 Hugo DeVries offered an explanation of the 

 origin of species, which he called mutation. He had observed in one 

 of the few vacant fields in Holland an evening primrose (Oenothera 

 Lamarckiana), which had been introduced from the United States. 

 Among the numerous individuals he found some so unlike the ordinary 

 form that he was compelled to regard them as distinct species, and in- 

 quiry showed that they had never been described. Plants of O. La- 

 marckiana and of the new species were removed to the garden at 

 Amsterdam and studied through many generations. 



It was found that when thousands of seeds of O. Lamarckiana were 



