298 Action of the Genetic Material 



sion, that is, opening of the nucleus, as opposed to the non-genie 

 function in polyteny without opening of the nucleus. A major diffi- 

 culty for such speculations would be the protozoan nucleus with intra- 

 nuclear mitosis. (See also the discussion in III 4 B.) 



In order to gain further insight, we may compare the structure 

 of what we just called supermicellar chromosomes, that is, the salivary 

 t)'pe of so-called polyteny with the structure of a large chromosome 

 which is active both genically and metabolically, namely, the lamp- 

 brush chromosome in the growing oocyte of Amphibia, which we have 

 discussed repeatedly (see I 2 A). According to Callan (1952), the 

 stretched lampbrush chromosome is actually of the diameter of a 

 single chain molecule. Guyenot and Danon (1953) find a diameter of 

 only 100-150 A°. It seems to me that we must conclude from such a 

 comparison that the genie action of the chromosome requires (in 

 agreement with Pauling's theory) a fully exposed surface of the pro- 

 teinic part of the nucleoprotein combination; while the non-genic 

 function of the chromosome (the mass production of a single protein) 

 requires a maximum number of identical templates which must be 

 sought in the DNA moiety of the chromonema. Such a view, which I 

 think is unavoidable in face of the facts, simultaneously disposes of 

 DNA as the genetic material. If Herskowitz (1950) is right that a 

 salivary chromosome is 1,000-stranded with corresponding increase in 

 amount of DNA (to 2^°), this alone would suffice to rule out DNA 

 as genie substance. Why should DNA increase immensely in cells with 

 a specialized secretory function, or growing without division, that is, 

 producing more cytoplasm? 



I have mentioned the possibility of heterochromatin being in- 

 volved in an erbungleiche division, though I pointed out that this 

 would not be exactly the same as development through intranuclear 

 genie diversification. Schultz (1952) has proposed a rather different 

 type of theory involving heterochromatin and resulting in an argument 

 in favor of intranuclear genie differentiation. This author starts his 

 deductions with the previously mentioned work of Painter and Rein- 

 dorp on the polyteny of nurse cells in the ovary of Drosophila. Here it 

 was observed that at a stage when the nurse cell nucleus is 512-ploid, 

 the heterochromatic Y-chromosome has divided only four times, and 

 other heterochromatic regions the same. Schultz thinks that "thus in 

 at least one case there is a differential multiplication of the various 

 chromosome regions, and the possibility is apparent that concomitant 

 with endomitosis a genetic differentiation of nuclei does take place." 

 This conclusion is, however, refuted ( apart from the foregoing analy- 



