vi] DEPOSITION OF YOLK 77 



peculiar behaviour in the growing oocyte can only be 

 ascribed to its activities in this connection. In some eggs 

 it may be seen that the first deposit of yolk takes place in 

 the immediate neighbourhood of the nucleus. It must 

 probably be supposed that in the early stages of gameto- 

 genesis, which correspond in the two sexes, the chromo- 

 somes are prepared for the "reducing" division which is 

 to follow, and to which the spermatocytes proceed directly, 

 while in the egg the framework, so to speak, persists, al- 

 though the chromatin particles are then distributed through 

 the nucleus in accordance with their function of control- 

 ling the growth of the egg-cell and the deposition of yolk. 

 Sometimes staining granules appear at this stage in the 

 neighbourhood of the nucleus (cf. PI. VIII, r), which 

 have been interpreted by some observers as chromatin 

 discharged from the nucleus into the cytoplasm in con- 

 nection with the deposition of yolk. Other investigators, 

 however, maintain that these granules are not chromatin, 

 but are true cytoplasmic structures, probably either mito- 

 chondrial in nature or belonging to the Golgi apparatus 

 to which reference has been made in an earlier chapter. 

 POPOFF (1907) -in the paper from which PI. VIII is taken, 

 points out that the granules, which superficially resemble 

 chromatin, stain in the manner characteristic of the Golgi 

 apparatus. 



In some animals, such as Mammals, although very little 

 yolk is deposited in the egg, there may be an extremely 

 long waiting period between the preliminary stages of the 

 maturation of the oocyte and the nuclear divisions which 

 complete them. In Mammals the oocytes develop as far as 

 the strepsitene stage before or shortly after birth, and the 

 actual maturation divisions do not occur till the egg is 

 ready for discharge from the ovary, so that in the longer- 



