JENNINGS: CHANGES IN HEREDITARY CHARACTERS 283 



idea of the genotype (Johannsen) , as the permanent germinal 

 constitution of any given individual ; it supported powerfully the 

 conception of Mendelism as merely the working out of recombina- 

 tions of mosaic-like parts of these permanent genotypes. The 

 whole conception is in its essential nature static; alteration does 

 not fit into the scheme. 



This discovery seemed to explain fully all the observed effects 

 of selection within a species; but gave them a significance quite 

 the reverse of what they had been supposed to have. It seemed 

 to account for practically all the supposed variations that had 

 been observed; they were not variations at all, in the sense of 

 steps in evolution; they were mere instances of the static con- 

 dition of diversity that everywhere prevails. Jordan, the devout 

 original discoverer of this condition of affairs, maintained that 

 it showed that organisms do not really vary; that there is no 

 such process as evolution; and indeed this seems to be the direct 

 logical conclusion to be drawn. In these days of plots and spies, 

 the evolutionists might almost feel that the enemy had crept 

 into their citadel and was blowing it up from within. 



Now, this multiplicity of diverse stocks really represents 

 the actual condition of affairs, so far as it goes. Persons who 

 are interested in maintaining that evolution is occurring, that 

 selection is effective, and the like, make a very great mistake 

 in denying the existence of the condition of diversity portrayed 

 by the genotypists. What they must do is to accept that con- 

 dition as a foundation, then show that it is not final; that it does 

 not proceed to the end; that the diverse existing stocks, while 

 heritably different as the genotypists maintain, may also change 

 and differentiate, in ways not yet detected by their discoverers. 



But of course most of the adherents of the "orthodox genotype 

 theory" do not maintain, with their first representative Jordan, 

 that no changes occur; that all is genetically static in organisms. 

 Typically, they admit that mutations occur; that the genotype 

 may at rare intervals transform, as a given chemical compound 

 may transform into another and diverse compound. We all 

 know the typical instances: the transforming mutations of 

 Oenothera; the bud variations that show in a sudden change of 



