ORGANIC EVOLUTION — PHYSICAL 27 



follows. A plant that varied favourably lias been 

 chosen, and a vast number of plants have been reared 

 from slips cut from it, the process being repeated 

 through any number of pseudo-generations. In this 

 way a single plant with a favourable variation is 

 multiplied into many similar plants, and the variation 

 is preserved for an indefinite time. Seeds reared from 

 such plants generally develop into inferior plants, but 

 exceptionally a superior plant develops, and is then 

 propagated as before by means of slips. The parent 

 variety is then ignored for breeding purposes and is 

 used only for stock on which to engraft the newer 

 variety. The more improved variety thus takes the 

 place of the variety which is less improved. This 

 process, the repetition of which has resulted in such 

 extreme examples of rapid evolution as the peach and 

 garden rose, is therefore a tremendously stringent 

 process of selection. Practically speaking the most 

 favourable individual of a species has been chosen and 

 multiplied by means of slips, the rest of the species 

 being eliminated ; and in each new seminal generation 

 the same process has been followed. It is as though, in 

 an endeavour to increase the height of men, we chose 

 the tallest man in the world, eliminated the rest of his 

 species, multiplied him — not by seminal generation, but 

 by some process analogous to the multiplication of 

 plants by slips — into thousands of men and women as 

 tall as himself, chose the tallest individual among the 

 cliildren of these, and repeated the process, and con- 

 tinued to do so through several seminal generations. 

 The process of selection under which the cultivated rose 

 and the peach have been evolved has tlierefore been, as 

 I say, tremendously severe — a thousand times more 

 severe than it is possible to make it among annual 

 plants and among the higher animals ; and their 

 evolution has therefore been extremely rapid — even 



