44 THE OVUM AND 



• 



nucleus of the yelk-cell ? If the former, it is in all probability 

 the most essential rudiment of the embryo ; but if it be the 

 nucleus of the yelk-cell its importance vanishes with the forma- 

 tion of the yelk-cell, and according to the analogy of most 

 cell-nuclei, it must either become absorbed altogether at a 

 subsequent period, or continue for a time simply rudimentary, 

 without forming any important new structure. The follow- 

 ing is the ordinary career of a simple cell : a nucleus is 

 present in the first instance ; around it a cell is formed j the 

 nucleus at first often increases in size as the cell grows, but 

 their growth is by no means proportionate, that of the cell 

 being much more rapid ; the cell-contents are at first transpa- 

 rent ; a firm precipitate or new formation next commences in 

 the cell, and this occurs immediately around the nucleus, 

 which is at first enclosed by it ; the nucleus then either 

 becomes entirely absorbed, or continues only rudimentary and 

 (with the following exception) I have never observed it to 

 give origin to any other essential formation. One or more 

 oil-globules once appeared to me to be formed during the ab- 

 sorption of the nucleus in the adipose cells within the cranial 

 cavity of a young carp. The importance of the decision of 

 this question in reference to the germinal vesicle thus becomes 

 very obvious. Unfortunately, however, neither the observa- 

 tions upon the subsequent relations of the germ-vesicle, nor 

 those on the origination of the ovum, are sufficiently extensive 

 or certain for the purpose. 



We shall next proceed to analyse both views of the question 

 more minutely, and afterwards compare them with the obser- 

 vations. If the germ-vesicle be a young cell, in the first place, 

 it is absolutely necessary that the yelk-cell should first exist, 

 and that the germ-vesicle should afterwards be developed within 

 it ; 2dly, the germ-vesicle must not be connected with the 

 vitelline-membrane, but must be developed free at some chosen 

 spot within the cavity of the yelk ; 3dly, the germ-vesicle 

 may be regarded either as a cell without a nucleus, and in 

 that case the spots of Wagner belong to the cell-contents, or 

 Wagner's spot, wdien it is single, is the nucleus; when there 

 arc several present, the others either differ essentially from one 

 particular spot, and pertain to the cell-contents, or they are 

 nuclei of young cells afterwards to be developed within the 



