50 THE OVUM AND 
usually takes place around the nucleus in other cells; and again, 
the germ-vesicle disappears, precisely as the nucleus of other 
cells is generally absorbed. There is then no evidence that the 
fluid of the germinal vesicle exercises a fructifying imfluence ; 
but if it be the cell-nucleus, it disappears, because it has com- 
pleted its office,—the formation of the yelk-cell. The dise, 
which has formed around it, becomes developed into the 
germinal membrane, and it is uncertain whether the remains 
of the germ-vesicle also take part in that formation. 
We shall next proceed to the consideration of the other 
contents which the yelk-cell includes in addition to the germ- 
vesicle, making use of the bird’s egg for the purpose. Setting 
aside some points of distinction of slighter importance, the 
globules, well known as present in the yelk of the hen’s 
egg when laid, may be divided into two principal classes: a, the 
globules of the yelk-cavity ; and 0b, those of the true yelk-sub- 
stance. The former (a) are not only present in the yelk-cavity, 
but occur also in the canal leading from it to the germinal 
membrane, and in the little prominence, called by Pander the 
nucleus of the tread (Kern des Hahnentritts). When many 
of them lie close together, they exhibit a white colour, whilst 
the true yelk-globules in such circumstances appear yellow. 
They may also be distinguished from the latter globules under 
the microscope, (see pl. II, fig. 2.) They are perfectly round 
globules, with quite smooth edges, each enclosing a smaller one, 
which is also perfectly spherical, and looks like an oil-globule, 
being rendered very distinct by its sharp outline. 
The remaining space in the large globules is usually trans- 
parent, and not granulous. But some may be observed which 
have granulous contents, and they then completely resemble 
the true yelk-globules, except that the latter do not gene- 
rally contain any smaller ones with such dark outlmes. Some- 
times also, the globules of the yelk-cavity contain two or more 
such smaller ones. The common yelk-globules (4), that is, 
those of the true yelk-substance, may be distinguished from the 
above-described by the following characteristics : they are upon 
the whole larger, they have all granulous contents, and, for the 
most part, donot enclose any smaller globules. They are very sen- 
sitive to the action of water, which causes them to fall to pieces, 
and then the granules enclosed within them becoming free, give 
