VARIATION AND HEREDITY 125 



uletely absent between these units as they 

 are betaken "the^olecules of "riiechegijsf." 



"The adoption of this principle influences 

 Our a.t.t.it.ijHe t.owfljfjfi thp! frhpory of flpsppnf*. 

 q ]] tlii] t t. japppipja. foft.vp a.rfg.pn 



from one another hv a. discontinuous, as 

 nppog-fifl f Q ^nin'-nnr^^ p-pftofigg Each new 

 unit, forming a fresh step in this process, 

 sharply and completely separates the new 

 form as an independent species from that 

 from which it sprang. 



it. 



t.ion 1 a.nd 



The ^itg.tion theory is opposed to that 



nf tL^ tillfftfy 



According to the latter view 

 the material for the origin of new species is 

 nffnrded by ordinary ^ r g ^~^^lled individnnJ 



C **C^ - * ^t/^ v 



According to the mutation theory 



iadjyiHiia.1 vnrintinTi ha.s nothi'ng to do with 

 Ik** primn r>f gp^m'^g This form of variation 

 . . . cannot even by the most rigid and sus- 

 tained selection lead to a genuine overstep- 

 ping of the limits of the species and still less 

 to the origin of new and constant characters." 

 "Of course ever eculirt of an oranism 



not, 



however, bvprdinary variation, but by a 



