276 Action of the Genetic Material 



discussion of nurse cells, I 2 B b dd.) Thus it is quite possible that 

 the immensely swollen germinal vesicle with its multifarious contents 

 does dismiss substances into the cytoplasm as well as keep some of 

 them until the nuclear membrane disappears. 



Actually, it is the oocyte nucleus (in addition to that of gland 

 cells) for which most morphological descriptions of extrusion of 

 materials have been described. Most of these are based upon the 

 study of stained material. This is true for the many instances studied 

 by my own school between 1904 and 1910 and in part for later work, 

 especially that of Schreiner (1916). But there are also reports of 

 observations of extrusion of "nucleoli" through the nuclear membrane 

 in vivo. For the discussion of the genetical problem the decisive point 

 is, of course, whether genie products, which must be assumed to be of 

 macromolecular size, can pass through the nuclear membrane and do 

 so. Today there can be no doubt that this is true. For the nuclear 

 membrane of the germinal vesicle Callan (see 1952) and Mazia (see 

 1952) showed with the electron microscope that rather large pores 

 are visible which permit the passage of particles of the size of 

 nucleoprotein molecules. N. G. Anderson (1953) assumes a rather 

 complicated structure, but with the same conclusions. Thus there can 

 be no doubt that the oocyte membrane is permeable in both directions 

 to molecules of the size needed for primary genie products. This is in 

 agreement with direct biochemical work on isolated tissue nuclei 

 which proves by direct analysis (including work with tagged mole- 

 cules) that an exchange in both directions through the nuclear 

 membrane can take place for large molecules (for details see Ander- 

 son's review, 1953). 



If we take it as proved that macromolecular genie products can 

 pass through the nuclear membrane, our problem still remains. Do the 

 primary genie products remain and interact with each other at the 

 chromosomal site until mitosis, when the contracting chromosomes 

 get rid of them and permit them to enter the cytoplasm? Or are these 

 products, when formed at the chromosomal surface, immediately 

 removed into the nuclear sap and do they enter the cytoplasm through 

 the nuclear membrane, or only at mitosis, or in both ways? Is it 

 possible that different types exist, that the genuine genie products, 

 meaning those responsible for hereditary determinations, are released 

 only at mitosis after interactions at the chromosomal site, while the 

 materials of secretion, the trophic materials, also formed under chro- 

 mosomal influence, are pushed immediately through the membrane? 



There are some facts available to answer such questions. All the 



