THE GAMETES 



35 



those present in the nucleoH can be found in the cytoplasm, particularly in 

 the immediate neighbourhood of the nuclear membrane, and it has been 

 suggested that the nucleoli are important sites for the synthesis of basic 

 protein-nucleates, which pass through the nuclear membrane and later 

 control the synthesis of further cytoplasmic proteins (p. 382). The extru- 

 sion of quite large droplets of nucleolar material into the cytoplasm can 



Figure 2.4 



An early and a middle stage in the development of the germitaal vesicle in 

 the oocyte of the snail Helix aspersa. The nucleus contains a large nucleolus, 

 and by the later stage shovioi there are many small nucleoli in addition. The 

 dotted region in the cytoplasm is the 'yolk nucleus'. (From Serra and Lopes 



I945-) 



be clearly seen in some forms (Fig. 2.5, p. 38). It is probable, indeed, that 

 ribose-nucleic acid compounds are some of the most important consti- 

 tuents in the cytoplasm of the growing oocyte, since they seem to be 

 involved in the protein synthesis which must be taking place very actively 

 there. During the grov^h of the oocyte they increase in amount, but not 

 as fast as the total volume of the cell (Osawa and Hayashi 1953). Caspers- 

 son and Schultz (1938) claimed that in Drosophila the quantity of such 

 nucleotides in the oocyte was increased in eggs formed in mothers which 



