FERTILISATION AND THE ORIGIN OF SPECIES. 331 



many years ; but it is probably all tliat is wanted to give 

 the crossed plant the ascendancy wben starting ou an evolu- 

 tionary career. 



As an illustrative case of a struggle between two varieties, 

 I took the same quantity of English-grown " Revett's " 

 wheat and Russian " Kubanka," the former having a pre- 

 ponderance of starch and the latter of gluten, being a smaller 

 and harder grain. I sowed them as thickly as possible on a 

 square yard, the two kinds having been previously well 

 mixed together. They all germinated, and the struggle of 

 course became intense. About twenty ears only were pro- 

 duced, which were all Kubanka. The experiment was 

 repeated a second year, with the same result. This is what 

 I would consider as, therefore, doe to " constitutional 

 selection." 



Survivors, however, are by no means entirely dependent 

 upon constitution, much less on specific differences ; for seeds 

 which fall on the circnmferenoe of the crowd, or on a better 

 soil than that upon which others may happen to lie, as on 

 stony ground, are thereby " selected," but it is through no 

 merit of their own, as in any way being the fittest, for they 

 survive only because they are the " luckiest ; " just as out of 

 the thousands of eggs of a salmon a few only escape the 

 jaws of their enemies : so that simply " good luck " plays an 

 important part in determining which shall survive and come 

 to maturity in both kingdoms alike. 



Hence, during the period of life when the straggle for 

 existence is most intense, there are varions circumstances 

 which determine what plants shall survive ; and in probably 

 few cases, generally no case, have the morphological variations 

 or specific characters any voice in the matter of selection 

 whatever, excepting indirectly, as stated above, whenever 

 constitutional vigour is correlated with first crossings. 



