278 Action of the Genetic Material 



proteins which comprise a major part of genie action. If this were so, 

 nothing in the detailed genie organization of the chromosome would 

 make sense. Obviously, the nucleolar apparatus responsible for the 

 production and transport of RNA is a generalized metabolic function, 

 which we called trophic, while the genie function, though dependent 

 upon DNA structure, is a strictly patterned, specialized process. If we 

 take together all the facts mentioned here and before, such con- 

 clusions seem unavoidable. 



It is not surprising, then, that masses of RNA may be followed 

 in the nucleus by Caspersson's subtle methods and, similarly, the 

 quantity of DNA as a whole by these and more recent methods, as 

 discussed before. Thus far, however, no way has been found to check 

 biochemically upon the primary genie products with which genetic 

 theory deals (though this may be possible one day for non-nucleated 

 microorganisms). The analyses of nuclear sap made by Callan (see 

 1952) reveal only different colloidal proteins, no nucleinic acids. In 

 view of the most recent work on the structure of the DNA molecule, 

 the question may be posed whether RNA, which in the end must be 

 derived from DNA, or, expressed more cautiously, may be made from 

 DNA, is not produced primarily in the chromosome and transferred 

 to the nucleolus, say for storage. An interesting finding by Stich and 

 Hammerling (1953) agrees better with Caspersson's view. They 

 isolated the huge nucleolus of Acetahularia and found that it takes up 

 avidly P^^ and synthesizes RNA. 



It is remarkable that all these recently elaborated facts tend to 

 return mutatis mutandis to apparently long-discarded views which I 

 developed half a century ago ( Goldschmidt, 1904 ) . Using R. Hertwig's 

 term "chromidia" for what was originally described as extranuclear 

 chromatin in Protozoa, I came to the conclusion that all intensively 

 active nuclei extrude "chromatin" from the nucleus in the form of 

 chromidia, which appear in many different forms in the cytoplasm 

 and are basic for its activities. It was further concluded that within 

 the nucleus two types of chromatin exist: idiochromatin and tropho- 

 chromatin; the former is the hereditary chromatin in the chromo- 

 somes; the latter, the trophic chromatin expelled from the nucleus as 

 chromidia. The two types were assumed to be a primary, always 

 present condition of the nucleus. In spite of errors in detail, the theory 

 is in a general way not much different from present-day ideas, if 

 idiochromatin is identical with DNA plus protein and trophochromatin 

 with RNA. 



At this point Rrachet's work on the biochemistry of differentiation 



