GERMINAL MEMBRANE. 45 
germ-vesicle. Before the spot can be considered to be the nu- 
cleus, it is necessary that it should, in the first instance at 
least, be connected with the wall of the vesicle. If, however, 
the germinal vesicle be the nucleus of the yelk-cell, it is 
essential, in the first place, that it should, in all probability, be 
present before the yelk-cell; at all events, that in proportion 
as the ovum is younger, should the vesicle be larger in relation 
to the cell; 2dly, it must, at first, he upon the vitelline- 
membrane, and be more or less intimately connected with it ; 
ddly, the germinal-vesicle, when regarded as a nucleus, either 
has no nucleoli, or Wagner’s spots are to be considered to re- 
present them; in the first case they form the contents of the 
nucleus. In the enumeration of these poimts, no regard is 
had to the relations of the germ-vesicle subsequent to impreg- 
nation, because it is desirable to determine its ultimate destiny, 
to a certain extent a priori, from its signification, and thus to 
be enabled at the least to afford a guide to the much moré 
difficult observation of the fecundated ovum. If the researches 
were complete, the distinctions above cited would be sufficient 
for the correct determination of the question at issue, the 
decision of the first pomt imdeed would of itseif be ample 
evidence. 
When we take into consideration the first point raised on 
either side, we should be compelled to decide in favour of the 
latter view, and regard the germ-vesicle as a nucleus, if it were 
proved to be first present, and also that the yelk-cell is formed 
around it as a simple cell, narrowly encompassing it in the 
first instance, and becoming gradually expanded. In the next 
place, it is certain that at an early period the germ-vesicle 
is much larger in proportion to the yelk-cell, and that it 
at first grows part passu with the yelk-cell, but that subse- 
quently the latter mcreases in size in a much greater ratio, 
whilst the vesicle remains stationary; and these are precisely 
the relations in which the vesicle should stand in order to be 
regarded as a nucleus. But these facts are not entirely irre- 
concilable with the first view. A young cell, the germ-vesicle, 
might be imagined to form within the yelk-cell at a very early 
period of its growth, which young cell might at first increase 
in size more rapidly than the original one, but cease to do so 
earlier, whilst the parent-cell might continue to be developed 
