4, 
DEVELOPMENT OF THE GENERATIVE ORGANS. 709 
In the case, however, of the Merdistic egg, where a number 
of cells unite to form the yelk, such an explanation of the 
nucleus is inadmissible. Most observers have solved the 
difficulty, however, by regarding one of the cells as a germ- 
cell and the remaining cells as yelk-cells. 
If such were the case, it is evident that some difference 
would be expected to exist between these cells, even from their 
earliest origin. 
Claus [840] thought he recognised a difference in the nuclei 
of cells of the young Merdistic ova; he says: ‘ The questions, 
the answers to which are of the highest importance, are—- 
whence is the germinal vesicle derived? and what are its rela- 
tions to the great yelk-cells ?? He answers these questions as 
follows: ‘I believe my own observations enable me to prove 
that the epithelial cells, the yelk-forming cells, and the germ- 
cells are modifications of identical elements.’ Which merely 
means that he found all the cells contained’in the youngest 
parts of the ovarian tubes precisely alike—a conclusion already 
arrived at by numerous observers. Yet Claus believes that 
in partially formed ova he could distinguish the egg-cell from 
the rest ‘by the smaller size and clearer contents of the 
nucleus.’ 
Mayer [812] thought that each egg contains several germinal 
vesicles, each making an attempt as it were to form an egg, 
the lowest only succeeding, and all the others perishing. 
I have examined hundreds of young insect ova to see if 
there is any difference in the nuclei, and I have entirely failed 
to find any. Sometimes one, sometimes several, are a little 
clearer than the rest, but there is no constant difference 
whatever. 
The terminal chamber of the egg-tubes is usually regarded 
as a germogen, in which germ ova are developed. Stein [819] 
appears to have been the first who distinguished the germinal 
chamber from the rest of the egg-tube and termed it the 
germ chamber (Keimfach). He regarded the cells in it as free 
from yelk; but no one has explained the origin of the yelk- 
cells, nor the manner in which the germ-cells of the terminal 
