SUPPLEMENT 
(REFERRED TO AT P. 46) 
ON THE SIGNIFICATION OF THE GERMINAL VESICLE. 
Wuen treating of the different parts of the ovum, in the 
foregoing work, it was found impossible to give a positive 
solution to the question as to whether the germ-vesicle was a 
young cell or the nucleus of the yelk-cell. Most of the facts 
before us were in favour of the latter view ; but if this were the 
correct one, the yelk-cell ought to be developed around the 
previously existing vesicle in such manner, that it in the 
first instance closely encompassed the latter, and afterwards 
became gradually expanded. This decisive observation was 
wanting, and the researches communicated by R. Wagner, in 
his ‘ Prodromus,’ rather tended to show that, in the formation 
of the ovum around the germinal vesicle, the membrane was 
not formed immediately around the vesicle, but that it inclosed 
at the same time a quantity of the granular mass in which the 
germ-vesicle lies. I was not at that time acquainted with a 
work of Wagner’s, which contained the facts necessary to a 
solution of the question, viz. his ‘ Beitrage zur Geschichte 
der Zeugung und Entwickelung., Erster Beitrag :’ from the 
‘ Mathematisch-physikalischen Klasse der K6nigl. Baierschen 
Acad. der Wissenschaften in Munchen.’ Speaking of the 
ovaries of insects, Wagner says, at page 45 :—* At the spot 
where the oviduct widens, the granular mass, which resembles 
the vitellme mass, becomes more plentiful; the separate germ- 
‘vesicles seem to be imbedded in it. I have so represented it 
in the ‘ Prodromus,’ fig. 18. Lately, however, it has appeared 
to me, as though the germ-vesicles with their germinal spots 
were actually already surrounded by a chorion and a perfectly 
pellucid yelk.” The accompanying illustration from Agrion 
virgo exhibits clearly how that which Wagner calls chorion, 
