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 al 

 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, lie upon the vitellinc- 

 membrane, and be more or less intimatelv connected with it : 

 3dly, 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 points, 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 t>> 

 be enabled at the least to afford a guide to the much more 

 difficult observation of the fecundated ovum. If the researches 

 were complete, the distinctions above cited would be sufficienl 

 for the correct determination of the question at issue, the 

 decision of the first point indeed would of itself 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 pari passu with the yelk-cell, but that subse- 

 quently the latter increases in size in a much greater ratio, 

 whilst the vesicle remains stationary; and these are preciselv 

 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 



