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, thcv are onlv 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 being regarded as a 

 young cell. 1 



"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. 2 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 ovum-cell (Eizelle.) Martin Barry, in- 

 deed, (1. 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 vesicle were a 

 germinal vesicle, around which no ovisac had as yet formed, or an ovisac within 

 which no c;enn-vesicle bad as vet formed. The occurrence also in the lower ani- 



