The Cytoplasm as Specific Substrate 203 



preserved for some time just as if by inheritance. But they remain 

 reversible in the same way, as the cellular constitution has not 

 changed. In classic genetic language this would mean, I think, a genie 

 alternative reaction norm with stability over some cell divisions, that 

 is, one of the general features of genie action and nothing of cyto- 

 plasmic nature. (The physical term "steady states," which has been 

 used to describe this situation, seems to be unnecessary as far as the 

 genetic facts are considered. The term "alternative norm of reaction" 

 covers the facts; I have used this concept repeatedly in these discus- 

 sions.) Thus no genuine cytoplasmic heredity is involved, and the 

 recourse to "plasmagenes," originally favored by Sonneborn, is ruled 

 out, Sonneborn (1955) formulates the lesult as follows: "The impor- 

 tant point is that alternative steady states based on mutual inhibitions 

 can give cytoplasmic inheritance without resort to self-dupHcating 

 cytoplasmic particles." I should prefer to say "can be erroneously 

 taken for cytoplasmic inheritance." 



Sonneborn thinks that the facts of antigenic inheritance generally 

 parallel those of Dauermodifikation. This would mean that the traits 

 showing Dauermodifikation are also gene-controlled traits (though 

 there are no facts available to prove this) with an alternative norm 

 of reaction which remains more or less self -perpetuating until internal 

 or external conditions switch it over. I wonder whether Jollos' original 

 data, especially the arsenic experiments, could be explained this way; 

 I doubt it. 



Some apparently unrelated facts may help this discussion. I am 

 thinking of the remarkable features of vernalization in cereals. The 

 traits involved, winter or summer wheat, are undoubtedly genically 

 controlled. But by appropriate treatment (e.g., with cold) at the 

 proper time the physiological alternative can be induced; for example, 

 winter wheat can be made to behave like summer wheat. This may be 

 described as an induced self-perpetuating cytoplasmic change. Self- 

 perpetuating may mean, as in the former cases, the presence of 

 changed self-perpetuating bodies like mitochondria, but it may also 

 mean a strictly alternative chemical property of the cytoplasm (a 

 "steady state"), which remains until forced again into its original 

 condition. The details (see Melchers' excellent discussion, 1952) are 

 as interesting for our present discussion as for plant genetics and 

 physiology generally, and may be described in the same terms as the 

 antigenic properties in Paramecium, involving an alternative norm of 

 reaction of the cytoplasm but not cytoplasmic inheritance. 



The materials presented in the last chapter and our analysis of 



