264 PHYSIOLOGICAL GENETICS 



evidence is available. In :t general way, a number of possibilities 

 are given. There is, first, the following alternative: Either the 



genie action, whatever it is, takes place within the resting nucleus, 

 or it is confined to the mitotic stage, when chromosomes and 

 cytoplasm are in direct contact. In favor of the latter possibility, 

 the facts may he mentioned regarding the relation of mitotic 

 divisions to determinative processes (see page 244). But these 

 facts may also be interpreted differently. In favor of the first 

 alternative, the behavior of egg cells of the determinative 

 type may be mentioned. In such cells, decisive developmental 

 processes, the chemodiffercntiation, occur in the resting nuclei. 1 

 Still a third possibility might connect the two alternatives, viz., 

 that the products of genie action are formed within the nucleus 

 but set free only when the nuclear membrane disappears. It is 

 known that at least in some eggs determinative processes are 

 started with the bursting of the germinal vesicle. 



Goldschmidt (1927c) and Koltzoff (1935a) have suggested a 

 connection between this phenomenon and the liberation of gene- 

 controlled substances formed during the growth period of the 

 nucleus. In a way, such views go back even to the discussions 

 upon the meaning of the nuclear and chromosomal behavior 

 in the auxocyte, centering around the terms idioehromatin and 

 trophochromatin (see Rueckert, 1899; Goldschmidt, 1904). In 

 a general way, it may then be assumed that the interaction of 

 genes and cytoplasm occurs through the nuclear membrane, 

 though other possibilities cannot be denied. This might mean 

 either of two things: (1) The direct products of genie action 

 diffuse through the nuclear membrane. As these products are 

 probably in the nature of catalyzers, either only low-molecular 

 catalyzers are involved, or the nuclear membrane must be 

 permeable for large molecules. (2) Substances from the cyto- 

 plasm enter the nucleus, and only the products of catalysis 

 return into the cytoplasm. There are only very few facts 

 available on which to base inferences. Most suggestive are the 

 strange and complicated intranuclear processes which occur in 

 the growing ovocytes of Selaehia and Amphibia and which 

 demonstrate an immense activity of the chromosomes, connected 



1 Quite recently Stern (Nature, Oct. 30, 1937) has drawn attention to the 

 fact that genie actions are known which occur within single cells during the 

 resting stage of the nucleus. 



