DISCONTINUOUS VARIATION 277 



imagining an asymmetrical nuclear division taking 

 place immediately before the formation of the germ- 

 cells, and this would lead us to expect a mutating 

 species to give rise to more than one new kind of 

 offspring at the same time. Such was actually the case 

 with the (Enothera Lamarckiana studied by de Vries ; 

 and this observation stands as the most complete piece 

 of evidence of a mutating species so far known to us. 

 We may be assured, then, that the complete potential 

 nature of new types as well as of old ones is already 

 laid down in the germ-cells previous to fertilization. 

 As Bateson puts it : ' For the first time in the history of 

 evolutionary thought Mendel's discovery enables us to 

 form some picture of the process which results in 

 genetic variation. It is simply the segregation of a 

 new kind of gamete, bearing one or more characters 

 distinct from those of the type. We can answer one 

 of the oldest questions in philosophy. In terms of 

 the ancient riddle, we may reply that the owl's egg 

 existed before the owl ; or, if we hesitate about the 

 owl, we may be sure about the bantam.'* 



Let us consider a little more closely the evidence of 

 mutation afforded by de Vries' studies of (Enothera 

 Lamarckiana. Semi-wild specimens of this species, 

 when transplanted and carefully observed, were found 

 to yield nearly 3 per cent, of seedlings which differed 

 definitely from their parent, and among these mutants 

 some fifteen distinct new sorts were described. Some 

 of the new species equalled or even surpassed the parent 



* British Association, Cambridge, 1904. Address to the 

 Zoological Section, p. 14. 



