MENDELISM 231 



to the Mendelian law. External conditions do affect 

 individuals in a most marked manner, but there is no 

 evidence that these changes in the environment produce 

 any change in the gametes formed by such individuals. 

 Since the publication of De Vries's Mutations - Theorie 

 in 1901, it has been customary to describe variations due 

 to specific factors as " mutations," while those which are 

 due to environmental influences are termed " fluctua- 

 tions " ; the former are inherited, the latter not. 



If you will now recall our discussion of the theory 

 outlined by Darwin in the Origin of Species, you will see 

 how these new discoveries have altered our whole outlook 

 on the evolutionary hypothesis as set forth in that epoch- 

 making work. It is wortn remembering that Mendel's 

 work was published only five years after the Origin 

 left the printer's hands, and one is tempted to specu- 

 late what would have been the form and fate of that 

 famous book had Darwin been acquainted with Mendel's 

 Experiments on Plant-Hybridisation. Perhaps, as Bateson 

 says, " the history of the evolutionary philosophy would 

 have been very different from that which we have 

 witnessed." Strangely enough, on the other hand, 

 Mendel, in his paper published in 1865, makes no refer- 

 ence to Darwin, although he does speak of " the spirit of 

 the Darwinian teaching," in his brief note on " Hieracium 

 hybrids " published in 1870. 



It will be useful to recapitulate at this point the 

 "natural selection" theory, so that the alteration in 

 point of view may be clear to you. 



The offspring of an organism inherits the fundamental 

 characteristics of its parents and yet no offspring resembles 

 its parent in every particular ; it occasionally shows 

 features that recall characters of its grandparents or 

 even of some farther back ancestor, and it also presents 

 individual idiosyncrasies of its own. Some of these 

 variations may be of such a kind as to lessen its chances 

 of success in the struggle for existence before it ; some, 



