48 THE OVUM AND 
the internal surface of it. Three is the largest number of 
nucleoli which I have observed in other nuclei, and Schleiden 
has in some very rare instances seen four in plants. If, how- 
ever, they are only the contents of the nucleus, and not 
nucleoli, it must be allowed that they differ very much from 
the contents of almost all other nuclei, which are generally 
yellowish, and made up of extremely minute granules. The 
only exception which I have met with was that already men- 
tioned respecting the nucleus of the adipose cells in the cranial 
cavity of a young carp. This last point seems therefore 
rather in favour of the germ-vesicle beg regarded as a 
young cell.! 
When the whole of the above detailed evidence is reflected 
upon in connexion, it will be seen that it is as yet impossible 
to decide the question as to whether the germinal vesicle be 
cell or nucleus, The opinion that the vesicle is to be regarded 
as a cell-nucleus, seems for the present to have the ascendancy, 
inasmuch as the observations upon the first and most important 
point, viz. the prior existence of the germ-vesicle to that of 
the yelk-cell appear to be in favour of that view.” The sub- 
1 Since in vegetable cells the nucleolus is the primary formation, and the nucleus 
a secondary one around it, and as the same has been shown to be most probably the 
case in animal cells, (see page 20, on the production of the nucleus of cartilage- 
cells,) so also in this case the signification to be assigned to Wagner’s spot depends 
upon the history of the development of the germ-vesicle. The observations of 
Wagner, quoted in the Supplement, show, however, that the single germinal spot of 
the ova of insects is first formed, and the germinal vesicle afterwards around it. 
The former must then be considered as nucleolus to the vesicle, which corresponds 
to the nucleus. When several of Wagner’s spots occur, their signification is totally 
different from that of the first one, and they are to be regarded only as secondary 
formations in the interior of the germ-vesicle. In fact, the younger the ova of fishes 
and frogs, the fewer spots are observed in them. 
2 The following is the probable course of formation of the ovum, according to the 
researches now before us; the ovisac (Eisach, ovisac of Barry, internal mem- 
brane of the Graafian vesicle) is first developed. In this (according to analogy 
with Wagner’s observations on the ova of insects) a germinal spot is generated, as 
nucleolus to the ovum. Around that spot the germinal vesicle is formed as nucleus 
to the ovum; and round this again the oyum-cell (Eizelle.) Martin Barry, in- 
deed, (I. c. p. 308,) conjectures that the germ-vesicle is formed previously to the 
ovisac; but my respected friend expresses himself with great caution on the ques- 
tion; and it would in fact be difficult to determine whether a given vcsicle were a 
germinal vesicle, around which no ovisac had as yet formed, or an ovisac within 
which no germ-vesicle had as yet formed. The occurrence also in the lower ani- 
