GERMINAL MEMBRANE. 49 
sequent relations of the vesicle seem also to afford evidence in 
its favour. The disc, for instance, is formed around it, and 
this perhaps corresponds to the granulous precipitate which 
mals of several ova in one ovicapsule is difficult of explanation by Barry’s view. 
In the further investigation of this subject, attention must continue to be fixed 
upon the possible, and even probable, existence of a nucleus to the ovicapsule. 
Wagner saw certain follicles in the mole, in which he could not detect a trace of 
any enclosed body. 
Wagner expresses himself in his new work (Lehrbuch der Physiologie, Leipzig, 
1839, p. 34) as being doubtful whether the vesicles met with in his observations 
on the preformation of the germinal vesicle in the ova of insects, were actually 
vesicles or not. The observations of Barry on the ova of mammalia and birds, 
are, however, in favour of the explanation of the ovum of the insect originally 
given by the first-named highly respected investigator, and therefore also of 
that which represents the germ-vesicle as nucleus of the ovum-cell. It is 
true it might be said, that, regarding the germ-vesicle as a cell, a second one, 
the ovum-cell was formed around it; but as opposed to that view, it must 
be remembered that no example of a second cell being formed around the first is 
afforded amongst all the other cells which exhibit a nucleus of the decidedly cha- 
racteristic form. The point in dispute, as to the interpretation to be placed upon 
the germ-vesicle, loses, however, somewhat of its importance if the theory which I 
shall propose (see the conclusion of the treatise) be received, inasmuch as [ shall 
there endeavour to prove the formation of the cell around the nucleus to be merely a 
repetition of the process by which the nucleus is formed around the nucleolus, and 
that the whole process of development of the cell may be reduced to a single or 
many times repeated formation of strata. The germinal-vesicle accordingly is the 
first stratum, or a cell of the first order; the yelk-cell the second stratum, or a cell 
of the second order. As above stated at page 47, a minute point was observed in 
the germinal spot by Wagner, and subsequently by myself also; and my respected 
colleague Vanbeneden lately found germinal spots in the ova of certain polypes 
(Genus Zoanthus), and also in ova of Anodonta, which had not as yet left the ovary, 
that appeared granulous, but at the same time seemed to be hollow, and some of 
which distinetly contained a very small round corpuscle. This observation accords 
most completely with the theory which regards the cells as produced by a stratified 
formation. This small corpuscle, which may be called a secondary nucleolus, would 
here be the primordial formation; the germinal spot would be the first stratum 
around it, that having in this instance become developed into a vesicle, in a manner 
likewise to be explained hereafter by the Cell-Theory; the germinal vesicle would 
be the second, and the yelk-cell the third stratum. The formation of even a fourth 
stratum, the albumen membrane, around the yelk-cell, would involve nothing con- 
tradictory to the theory ; but in such case we certainly could not avoid regarding it 
as a second cell, which had become formed around a previously existing one: for 
the yelk-cell cannot well be considered to be a nucleus. The mode of formation of 
this albumen membrane must, however, in the first instance, be ascertained by in- 
vestigation. 
4 
