Genie Control of Development 289 



material within the nucleus itself diversifies. Further, the qualitative 

 part of nuclear control of cytoplasmic processes, that is, the bio- 

 chemical meaning of the words "nuclear control," should be estab- 

 hshed. Finally, independent or at least self-perpetuating cytoplasmic 

 processes have to be considered. 



A. THE QUALITATIVE ASPECT 



a. Nuclear versus cytoplasmic diversification 



It is well known that Weismann conceived of development, as far 

 as genetic control is concerned, as a sorting out of genetic material 

 by erbungleiche Teilung. With the rise of genetics and cytogenetics, 

 this idea was abandoned. It became clear that the phenomena of 

 embryonic restitution and of regeneration as well as the presence of 

 the same chromosomes in all cells did not agree with such an assump- 

 tion. In the case of the salivary gland chromosomes of Drosophila, 

 located in cells at the extreme end of development, there is no doubt 

 that in a purely material ( not functional ) sense the entire genie mate- 

 rial is present in its normal architecture. Numerous facts point in the 

 same direction: the most instructive are the existence of cell lethals 

 (Demerec, 1943) and the local effects of somatic crossing over in 

 peripheral cells ( Stern, 1936 ) . However, recently some geneticists and 

 biochemists have taken up again the apparently long-settled problem 

 and asked themselves whether there is not also a nuclear diversifica- 

 tion in development after all (e.g., Spiegelman, Schultz). 



Let us first consider what the question in itself means. Certainly, 

 no independent action of the nucleus is imaginable, since the nucleus 

 always collaborates somehow with the cytoplasm. Even apparently 

 purely cytoplasmic features are known to be genically controlled, as 

 I have stated repeatedly before. I mentioned previously the maternally 

 inherited and simple Mendelian control of the bending of the spindle 

 and spiral arrangement of cytoplasmic particles in the mollusk egg, and 

 the diverse cases of cytoplasmic conditioning. The abnormalities in 

 the formation of sperm tails in Drosophila crosses (Dobzhansky, 1933) 

 constitute another example. After all, genie control of meiotic be- 

 havior of the chromosomes ( see Beadle's sticky and asynaptic chromo- 

 somes) also belongs here. Thus, visible cytoplasmic differences re- 

 sulting in unequal divisions, in regard to both potency and visible 

 differentiation, do not necessarily mean that the genie material is not 

 involved. 



But this is not our present problem. What we want to know is 



