xxxiv MUTATION, MENDELISM, ETC. 



are the words in which Bateson at the outset of his 

 work 1 truly states the problem to be solved. Hardly 

 any assistance in this solution is afforded by the 

 Mendelian discovery. In the case of heterostyled plants, 

 Darwin had already proved that both forms exist in 

 Nature, and that in fact the offspring do arrange 

 themselves in two groups of approximately equal 

 numbers. The gametic explanation of this, although 

 intensely interesting, carries us no step further on the 

 road of Evolution. Furthermore, Darwin showed what 

 is the meaning of the heterostyled condition in the life 

 of the plant, and thus explained how it was that the 

 character has been selected, and incorporated into the 

 structure of the species. To look on this record and 

 on that, and maintain that Darwin failed to solve the 

 problem which the Mendelian has now solved, is, to 

 put it as mildly as possible, unreasonable and absurd. 



It is probable that the part played by Mendel's prin- 

 ciple in evolution is limited to the prevention, in certain 

 cases, of the supposed ' swamping effect of intercrossing '. 

 Interbreeding between a species and its variety could not 

 obliterate or weaken the latter when the relationship of 

 the two forms is Mendelian. As explained on pp. xxix, 

 xxx, a Mendelian variety would never really fuse with 

 the parent form, but would sooner or later emerge pure 

 in some future generation. On the other hand, the 

 characters of the variety, unless favoured by selection, 

 are prevented by the same principle from penetrating the 

 mass of the species. The average numbers of adults in 

 successive generations remaining constant, the number of 

 adult descendants of a new variety (with fertility equal 

 to that of the parent species) would, unless subject to 

 discriminative selection, remain constant also. 



1 On Variation, p. i. 



