Guar, “I. ORIGIN OF THE EGG. 457 
so as to be completely hidden by the peduncle of the calyx. Originally this vesicle 
is a collection, in a globular form,— against the wall of the egg cell, (Pl. 8, fig. 1, 
j, 4) where it always remains,—of a less refractive, lighter, and more albuminous 
substance than the surrounding medium; yet, until the former has assumed a certain 
density, dissimilar from the latter, the refraction of the two is so nearly alike that we 
cannot perceive the difference, but soon there ensues a period when they are faintly 
distinguishable from each other, and at last every thing becomes clear and unmis- 
takable. 
becomes apparent, even after the germinal dots, or, viewing the egg as a cell, the 
It is not, however, till a much later period that a well defined wall 
nucleoli of the egg cell, have developed themselves to a certain degree (PI. 8, fig. 
8a); yet we have strong presumptive evidence that a layer of more coherent 
substance is present at the surface, just as in the case of the yolk parent cells, 
and also in the case of the dots of the germinal vesicle belonging to a much 
larger egg, which will be described when speaking of the growth of this vesicle 
in detail. Again, when water is brought in contact with the vesicle, it swells 
slightly, and then bursts, just as if a membrane had suddenly given way; whereas, 
If it 
is homogeneous from centre to superficies, why does it not spread and mix with 
were the mass homogeneous throughout, it would fall to pieces gradually. 
the yolk, as happens after the sudden bursting consequent upon pressure? We 
ean hardly want further evidence, except an actual view of the membrane, to 
feel satisfied that it is present, although in a less palpable form than it is usual 
to acknowledge as such. 
So far we have followed the growth of the egg, as a whole, up to that point 
where it has gained all its characteristics, and thus disclosed the mode of its 
origin, and proved that, what was once a mere granule-like cell, is developed into 
that which is called an egg, and yet still remains a cell The further progress of 
the ege contents, namely, the yolk, the germinal vesicle, and its dots, is so com- 
plicated, that each part must be treated separately, in order to avoid confusion, 
and also to lay particular stress on every one, since the several components have 
a feature peculiar to each, and entirely different from any other. 
1 Tt is contended, by some investigators, that the 
ege cannot be looked upon in the light of a cell, be- 
cause of its subsequent complication. True, it is not 
necessary to insist that it is identical, as a body, with 
the cells of animal tissues; it is nevertheless a cell, but 
a cell of peculiar derivation and destination, the sim- 
plicity of which, as well as its similarity to those among 
58 
which it originates, is very early lost in the highly 
organized nature of its succeeding developments. 
Again, these authors, Thompson (loc. cit., p. 135) at 
least, advocate that the germinal vesicle being, as 
they erroneously hold, the primitive basis of the 
ege, is more probably the true egg cell, and the 
whole ovum a complex cell. 
