240 FINE-STRUCTURE OF PROTOPLASM II 



cation of the chromonema threads during cell division; but then the 

 question arises as to why protein synthesis is only necessary in the 

 chromomeres and how the anucleal parts of the thread augment their 

 protein substance. According to this theory, nucleic acids would be 

 also temporarily necessary in endomitotic division (Geitler, 1940; 

 Berger, 1 941), though hitherto this has evaded observation. In what- 

 ever way the function of the nucleic acids as synthesizing protein 

 enzymes may be confirmed or modified in the future, it will not irre- 

 concilably contradict the propounded hypothesis of screening, as in 

 both cases nucleic acids must be assumed to accumulate in the genet- 

 ically active regions, as a result of which the chemical activity of the 

 genes is, for the time of multiplication, paralyzed. 



ScHULTZ (1941) goes one step further and calls the genes nucleo- 

 proteins, that is to say nucleic acid compounds. He declares that the 

 genes and nucleoproteins have in common the properties of speci- 

 ficity, auto-reproduction, similar distribution in the cell and intimate 

 relation to synthesis processes. There is this much to be advanced 

 against this opinion : that the activity of the genes only begins in the 

 reconstituted nucleus, whereas in that state the nucleoproteins dis- 

 appear very much into the background. Hence, after their duplication 

 and division, the genes must be independent, to a large extent, of the 

 nucleic acids, making their influence felt in the growing cell, without 

 having the character of nucleoproteins. 



Identical auto-reproduction of nucleoproteins (comparison with virus protein). 

 Whereas in this monograph the genes have been compared morphologically 

 and chemically with enzymes, the literature inclines rather to draw the 

 analogy with the rod-shaped virus particles, notwithstanding the fact that 

 important points of comparison have lost cogency since the invalidation of 

 the classical fibrillar hypothesis of the chromosome structure. Many of the 

 varieties of virus isolated so far are of similar chemical composition to 

 chromatin: they are «»r/i?o/)ro/f/«j-, i.e., proteins of polypeptides and nucleic 

 acids. They do, it is true, still contain lipids and, under some circumstances, 

 also small amounts of polysaccharides. Minute amounts of lipid have also 

 been detected in chromosomes (Hirschler, 1942), though as a rule those 

 components are disregarded in discussions on the structure of chromatin. 

 It is the virus of tabacco mosaic disease which has been subjected to the most 

 exact analysis, as Stanley's method (1958a) provides a suitable means (by 

 precipitations) of obtaining it in a crystallized form. It contains 1.7 to 

 5 % of nucleic acid, according to its preceding treatment. If the nucleic 

 acid is separated off, the virus protein loses its pathogenic properties and 



