244 Cytoplasm as Seat of Genetic Properties 



gene. This idea, though always highly speculative, has lost any sense, 

 I think, since we know that viruses are highly complicated organisms. 

 There are, of course, very different kinds of viruses. The crystallizable 

 plant viruses, being RNA in nature, are a special group which at 

 present it is rather difficult to compare with animal viruses and bac- 

 teriophages. At the other end are the microscopically visible Rickettsia 

 (and kappa particles), which possibly have a still higher level of 

 organization. The best information (I mean for the geneticist) comes 

 thus far from bacteriophage and animal viruses like the influenza 

 virus. There is no doubt that these have a complicated structure 

 permitting mutation, genetic recombination, linkage, and even Hnkage 

 groups (most recent reviews in Cold Spring Harbor Sympos. 18, 

 1953 ) . Thus a comparison with a gene is ruled out. But it is true that 

 in the life cycle of a virus a vegetative, non-infectious phase occurs 

 in which the particle seems to be free of protein and consists mainly 

 of DNA. In this provirus condition in which the recombinations occur 

 the genie level may be represented. The amazing facts and theories 

 recently discovered at this level will certainly sooner or later lead to 

 information on the genie material as such, and also on unexpected 

 variants of its behavior on the organizational level of a virus or phage. 

 However, they exclude so completely the somewhat naive theory of 

 the identity of viruses, plasmagenes, and genes that a further discus- 

 sion is hardly needed. Much of the confusion stems, I think, from the 

 identification of self-reproducing particle with a gene, as we discussed 

 earlier. While refusing to accept what I consider to be unwarranted 

 identifications of viruses and genes and statements to the effect that 

 genes, plasmagenes, and viruses cannot be kept apart any longer, I am 

 certain that the special features of bacterial and virus genetics will 

 eventually help us to formulate exact ideas on the nature of the genie 

 material. But this is completely different from the more or less 

 gratuitous comparisons of the unknown gene, the more than dubious 

 plasmagene, and the collection of organizational levels called viruses. 



