THE MUTATION THEORY 



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of every progeny. The germ plasm seems to be a system 

 capable of existing in several different states of equi- 

 librium. Some of these equilibria may be thought of as 

 stable, others as metastable, others as labile, to borrow 

 terms from the physicist. The germ plasm of different 

 species may undergo parallel transformations, resulting 

 in parallel variations. All who have dealt with the spe- 

 cies of large genera know that oftentimes the same series 

 of variations turns up in one collective species after 

 another. Many characters have arisen independently, at 

 so many points in different lines of descent, that they 

 have no phylogenetic significance whatever. 



It seems to the speaker that the Oenothera situation is 

 clearing up. More and more evidence is accumulating 

 which shows that although the phenomena are complex, 

 they are orderly. Probably no two of the workers on the 

 (Enothera problem look at it from the same point of view. 

 In this paper I have not hesitated to state freely my 

 present working hypotheses. Xext year they may have 

 changed, to fit new facts. Even now there are data at 

 hand which do not accord with the best hypotheses I have 

 been able to formulate, but neither do they accord with 

 any others. Under the circumstances, one should not 

 draw conclusions of too sweeping a nature. It may con- 

 fidently be stated, however, that the appearance of muta- 

 tions in (Enothera is not due to Mendelian segregation, 

 and that the Mendelian method of attack has been utterly 

 fruitless. It is freely admitted that the mutation proc- 

 esses themselves are hardly understood at all, and that 

 further work must decide whether or not mutation is 

 always or ever conditioned by previous hybridization. 



Bateson has recently described the genetical behavior 

 of the rogues which occur in certain varieties of peas. 

 Although he does not suggest that these strange forms 

 are mutations, his evidence would tend to convince a mu- 

 tationist that they are. Would it not be a strange turn of 

 fate if Bateson, the leader of the Mendelian school and 

 critic of de Yries, were destined to discover mutations of 

 a non-Mendelian type in the very genus which provided 

 Mendel with the material for his classical researches? 



