NATURAL SELECTION. 



577 



ditions of life. But, whether their malformations are "injurious" or 

 " inadaptive," and therefore " mortal," can only be found by experiment. 



It must be understood that the conclusion of present-day ecologists, 

 which has so completely corroborated Darwin's letter to Wagner, is not 

 based on the study of a single group of plants, whether ferns or others, 

 but upon the geographical distribution of the whole vegetable world — as 

 Dr. Schimper has shown — and as, perhaps I may add, my own books in 

 the "International Scientific Series " also demonstrate. 



Geobge Henslow. 



