Genetic and Non-Genetic Variation 285 



between these three phenomena in bacteria with imperfect — 

 or imperfectly understood — sexual mechanisms? Not being 

 a bacterial geneticist I would rather ask the question and hope 

 that the discussion will bring the answer. However, I am 

 prepared to accept as information events all such phenotypic 

 changes — spontaneous or induced — which can be passed on 

 to other cells through either transformation, transduction or 

 recombination. As regards "translation events", in higher 

 organisms cytoplasmic inheritance (maternal inheritance) is 

 identified by means of reciprocal crossing experiments. Is 

 there, in bacteria, the equivalent of a reciprocal cross in 

 (a) transformation experiments, (b) transduction experiments, 

 and (c) recombination experiments? 



Receptor events would be phenotypic changes which in 

 experiments involving reciprocal crosses cannot be passed on 

 to the other cells through transformation, transduction or 

 recombination. This should decide whether a bacterial 

 character should be considered heritable (genetic) or non- 

 heritable. However, what weight can be placed upon nega- 

 tive evidence in transformation, transduction or recombina- 

 tion experiments in bacteria? Two of these mechanisms 

 transmit only a fraction of the genetical information from 

 one cell to another. How much can we therefore conclude if 

 a character cannot be passed on through transformation, 

 transduction, etc.? 



Anticipating that bacterial geneticists may be unable to 

 give full assurance on this point, I propose to consider other 

 possibilities for approaching the problem, by studying the 

 reaction of the cells to various chemical treatments. Naturally 

 this evidence can never be more than circumstantial. 



The last 10-15 years have provided a good deal of informa- 

 tion (Table I) about the response of the receptor system, as 

 well as the translation and information system, to chemical 

 treatment. Table I shows that radiation, temperature and 

 alkylating agents have such a non-specific and general effect 

 on the biological systems that they cannot discriminate 

 between different specific events. However, phenocopies in 



