148 Gates, Tetraploicl Mutants and Chromosome Mechanisms. 



mutant types as Lamarcldana itself. 0. gigas is therefore, like 

 O. rubricalyx, a progressive mutant in the sense of de Vries. 



10. Hence although some of the characters in Oenothera are 

 Mendelian in their behaviour after they have arisen, yet Mendelian 

 combinations in the sense of Nilsson are wholly inadequate to 

 account for their first appearance. 



11. I am, however, in agreement with Nilsson that many at 

 least of the mutant differences are due to changes which are fun- 

 damentally quantitative. Many of the size-differences in the races 

 with higher chromosome numbers are also probably due to differ- 

 ences in the number of chromosomes in their cells. It is the duty 

 of the observer to analyze these differences as far as possible in 

 terms of chromosome-number and cell-size. Evidently, any explana- 

 tion of the mutation phenomena in Oenothera which neglects the 

 cytological facts, is on very unsafe ground. 



Literature Cited. 



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