526 THE AMEBIC AX NATURALIST [Vol. L 



Heribert-Nilsson refers to (I give a literal translation) 

 as " heterogamous combinations which are recessive only 

 in the female gametes, but in the male gametes continuously 

 heterozygous." As far as I can interpret this vague 

 statement at all, it involves a decidedly unique concep- 

 tion, namely, that the individual 2x mutation embodies 

 two different kinds of germ plasm, a homozygous female 

 germ-plasm which will give one kind of cells when the 

 reduction division takes place, and a heterozygous male 

 germ-plasm, which will give two kinds of cells. I think 

 that no one will be inclined to adopt this altogether revo- 

 lutionary and useless hypothesis. It is by no means cer- 

 tain, after all, that the mutations which show the type of 

 inheritance in question do not belong to the class with 

 irregular chromosome numbers. With one exception they 

 have not been examined cytologically. Oenothera lata, a 

 mutation which shows this type of inheritance, has 15 

 chromosomes. Consequently there is an opportunity for 

 the formation of two kinds of gametes, with 7 and 8 chro- 

 mosomes, respectively. The male gametes with 8 chro- 

 mosomes appear to be eliminated. As a result, zygotes are 

 formed with 7 + 7 = 14 and 8 + 7 = 15 chromosomes. The 

 former are (E. Lamarchiana, the latter are (E. lata. This 

 beautiful correlation of cytology with inheritance has 

 been worked out by Gates and Thomas. 



In either event, whether the mutations which throw the 

 specific type in every generation have a regular or an 

 irregular chromosome number, the mutation Irypothesis 

 provides a far more plausible explanation for their be- 

 havior than the Mendelian hypothesis. 



It must be clear by this time that the speaker finds 

 incredible the arguments that have been brought forward 

 in favor of the idea that mutation and Mendelian segre- 

 gation are the same. Doubtless it often happens that a 

 mutated germ cell fuses with a typical germ cell and pro- 

 duces an ordinary Mendelian heterozygote. If the mu- 

 tated character is recessive, and the dominance is com- 

 plete, the first hybrid generation will of course resemble 

 the parental type, and the second hybrid generation will 



