40 J. BKONTE GATENBY 



13. The pcripheml granules of both types later disappear 

 or become hidden by the formation of clouds of nucleolar 

 deutoplasm. 



Oogenesis. 



14. By staining, fixing, and by centrifuge experiments it 

 can be shown that the full-grown oocyte of Saccocirrus con- 

 tains four distinct kinds of formed ' yolk '-granules, i.e. Golgi 

 elements, mitochondria, true yolk, nucleolar extrusions or 

 nucleolar deutoplasm. (See their fixing and staining reactions 

 in a table on p. 18.) 



15. The most numerous and chemically most resistant granules 

 are neither mitochondria nor Golgi elements, but are derived from 

 nucleolar extrusions. At a very early stage the oocyte nucleolus 

 buds off pieces which pass through the nuclear membrane, 

 but at first remain stuck on its outer surface (stages in PI. 3, 

 figs. 23, 24, and 25, nl). At one stage these nucleolar deriva- 

 tives form an extraordinary picture, being stuck all over the 

 nucleus in the form of pyramidal bodies, whose base adheres 

 to the nuclear membrane (PI. 3, fig. 23). The nucleolar deriva- 

 tives stain intensely in haematoxylin or fuchsin (fig. 23), but 

 only go yellowish in osmic acid (fig. 21). 



16. Later on these pyramidal granules lose their connexions 

 with the nuclear membrane, but, remaining quite near, become 

 the centres of numbers of large vacuoles which appear (PI. 4, 

 fig. 29). Inside these vacuoles the nucleolar granules partially 

 break up, and subsequently, after the absorption of the 

 vacuoles, the granules move out further from the nuclear 

 membrane and form clouds of granules in the egg cytoplasm 

 (PL 4, figs. 30 and 34). The marked vacuolar stage in the 

 history of the egg seems to occur with suddenness, and is not 

 discoverable at this period in all eggs of this size (PI. 4, fig. 29). 

 It is just about this stage that great activity is noticeable 

 around the periphery of the nucleus, as shown in PI. 4, fig. 35, 

 by formol-silver nitrate technique. The nucleolar deutoplasm 

 forms dense clouds of heavy granules throughout the entire 

 egg cytoplasm. 



17. If the ovary of Saccocirrus be prepared by a silver 



