JOURNAL 



OP THE 



Royal Horticultural Society. 



Vol. XXXIII. 1907. 



THE TRI E DARWINISM. 

 By Rev. Professor G. Henslow, M.A., V.M.H. 



[Lecture given on March 5, 1907.] 



Qp to the middle of the last century we all thought that each species of 

 animal and plant was created by a direct fiat, somewhat as Milton so 

 graphically described in his " Paradise Lost." Darwin, however, revived 

 the doctrine of Evolution, about which philosophers had speculated in 

 times past ; but he put it forward in a more attractive form, so that it was 

 soon accepted, not only by biologists, but by all the world as well. 



Darwin, however, went further, and propounded a theory of the method 

 of Evolution. This is called "Darwinism," and is defined by the title of 

 his book, " The Origin of Species by Means of Natural Selection " (1859). 



Darwin based this theory upon the following, partly true and partly 

 hypothetical statements : 



1. Variability, or the capacity of varying, which, under changed 

 conditions of life, produces new structures. 



2. The production of seeds is enormous ; but only the usual average 

 of adults occurs in nature ; the majority die. 



3. All plants show "Individual Differences " ; and when a number of 

 seedlings of the same species grow up under new conditions of life or 

 environment, Darwin assumed that of their individual differences some 

 would or might, by chance, be "favourable," i.e. structures adapted to the 

 new surroundings ; while others, the majority, would be " injurious," 

 i.e. inadapted, and consequently fatal variations ; as Weismann observes 

 of even slight variations, they may be a matter of life or death to the indi- 

 vidual — a pure assumption, based on no evidence. 



This mixture of good and bad seedlings Darwin called the " Indefinite 

 Results of the Direct Action of the New Conditions of Life." 



4. Presuming the preceding to be true, Darwin now introduced 

 " Natural Selection " ; by which he meant that, in the struggle for life, 

 the individuals with favourable, i.e. adaptive variations, would survive ; 



B 



