226 _ TRANSACTIONS OF THE [may 13, 
membrane that the latter seems broken at this point. In many 
cases the granules lie partly without (fig. 2). In slightly older 
eggs the mass of granules—the yolk nucleus—is much enlarged 
but still lies close to the nucleus. At this stage many fibrous 
but granular processes can be seen extending out into the cyto- 
plasm (figs. 2 and 3), while aggregates of the granules begin 
to break off from the main mass (fig. 3). This marks the disin- 
tegration of the yolk-nucleus. In older eggs the yolk-nucleus 
moves away from the nucleus, the disintegration continues, and 
the egg then contains a great number of smaller granular masses 
each with several fibre-like prolongations. At this stage the 
nucleus begins to enlarge and to change into the germinal vesi- 
cle. Next the disintegrated masses lose their granular structure 
and become large and homogeneous, forming the yolk plates of 
the egg (fig. 5). In all of these latter stages the nucleolus lies 
intact within the germinal vesicle (figs. 4 and 5). 
The position of the yolk-nucleus on and near the nuclear 
membrane favors the view that it is of nuclear rather than of 
cytoplasmic origin; and the lack of a membrane at this portion 
of the nucleus adds strong evidence in favor of such an origin. 
A critical examination of the chromatin network inside of the 
nucleus leaves no doubt that such is the case. The yolk nucleus 
is in direct connection with the chromatin, not at one point only, 
as Van Bambeke pictures for Scorpena, but at many points 
(fig. 2). In some cases one half or more of the yolk-nucleus lies 
inside of the nuclear membrane, while great strands of chroma- 
tin stretch from it to the opposite side of the nucleus. In 
other cases only two such strands will be seen, but in all cases 
there is direct connection between the granular mass outside 
and the chromatin mass inside. 
As the yolk nucleus moves away from the nucleus all connec- 
tions are broken between it and the chromatin. It appears as 
an independent body, while the nucleus regains its intact 
membrane and then begins its metamorphosis into the germinal 
vesicle. The yolk-nucleus does not again come in contact with 
the nucleus. 
It appears, therefore, that in Lumbricus the yolk-nucleus ts not 
only of nuclear origin, but is derived from the chromatin, the nu- 
cleolus of the germinal vesicle taking no part in its formation. 
It does not appear thus far, however, whether the yolk 
nucleus is indirectly derived from the chromatin as a product of 
metabolic activity or whether it is directly derived by bodily 
disintegration of the chromatin. This question cannot be set- 
tled by examining the position of the yolk-nucleus. It is in 
direct communication with the chromatin network, it is true 
