Genie Control of Development 305 



ferentiation having taken place in the cytoplasm, as derived above 

 with the model of the lepidopteran scale. 



b. Biochemical attack 



In a former chapter the biochemical theories of primary genie 

 actions as well as those of intranuclear behavior of the nuclear con- 

 stituents were discussed. At that time we pointed out that we would 

 return to those aspects of the problem which involve the removal of 

 nuclear products into the cytoplasm. Whether the primary products 

 of the genie material are formed at the chromosomal site or not, and 

 whether within the nucleus other than primary genie products appear, 

 the genie control of development requires that such products enter 

 the cytoplasm and in some way control the orderly series of deter- 

 mination processes of which typical development consists, which 

 includes also the possibility that cytoplasmic conditions initiated by 

 the genie material in the nucleus become subsequently self-perpetu- 

 ating. We have already seen that according to Caspersson at least one 

 derivative of chromosomal material is involved in nucleoplasmic 

 exchange, ribonucleic acid which was derived from DNA and first 

 stored in the nucleolus and finally appears at the nuclear surface. We 

 paralleled these facts with the old ideas of idio- and trophochromatin 

 and discussed the requirements for a genetic meaning of these sub- 

 stances. If RNA released into the cytoplasm is the actual genie product 

 in control of differentiation, there should be as many RNA types as 

 there are different genie materials, and differentiation would consist 

 mainly in their being sorted out. 



The role of biochemically characterized substances in the cyto- 

 plasm supposed to be in control of its determinative processes has 

 been much studied in the last decades by the experimental em- 

 bryologists and most prominently by J. Brachet and his school 

 (summaries of Brachet's views in 1949, 1950a,fe). We are not in- 

 terested here in the processes of growth and development per se, but 

 only in the question whether or not the chemistry and behavior of 

 genie products reaching the cytoplasm or primary cytoplasmic sub- 

 stances explain the riddle of how the genie material controls orderly 

 differentiation. The geneticist would wish for a solution of such 

 questions as: Are substances known which enter the cytoplasm as 

 genie products? Are they as diversified as must be assumed, if they 

 are in control of all the different processes of embryonic differenti- 

 ation? In this case does a mechanism for their proper sorting out exist? 



