OF PLANOCERA ELLIPTICA. 
15 
YI. 
THE GERM1NATIVE VESICLE AND GERMINATIVE SPOT. 
The process of the division of the yolk is no sooner started, than the germinative 
vesicle and the germinative spot disappear as vesicles ; their contents, then, mix with 
the yolk. But whether this mixture has any influence upon the process of the divi- 
sion, is difficult to determine. For a long time embryologists thought that the division 
of the yolk was dependent upon the previous bursting of these vesicles, butone instance 
is known now, in which the germinative vesicle is still present, when the yolk is already 
divided into several spheres. I cannot help thinking that the germinative vesicle 
and the germinative spot or spots (for there are sometimes several germinative spots 
in other types), have no initial power towards the future stage of development, and 
that their existence during the first period of the egg’s history, only reminds us of 
the origin of the eggs in the common laboratory of organic substances. 
The contained matter of the germinative vesicle is transparent; its structure w r as 
beyond the reach of the microscopic powers at my command. 
VII. 
THE CLEAR SPACE IN THE SPHERES OF DIVISION. 
Another phenomenon connected with the division of the yolk, be the division regular 
or irregular, takes place during this period of the egg’s history. 
The vitelline sphere is no sooner divided into two parts, than in the centre of each 
of these parts a clear space appears, and as the number of the spheres of division in- 
creases up to the mulberry shape, in the manner above stated, each of the spheres of 
division exhibits that clear space, however small those spheres may be. 
In its general appearance, this clear space reminds us of the germinative vesicle, 
from which it differs, however, in not being circumscribed by a defined membrane, 
whence its vague outline, and also in being proportionally larger. That it has nothing 
in common with the germinative vesicle, is satisfactorily shown in the case where the 
latter still exists when the yolk presents several spheres of division, each of which 
being provided with its own clear space, 
1 he clear space of the spheres of division, therefore, is a phenomenon which indicates 
in the egg something else than matter, a vital activity every where present in the 
yolk, endowed with the same power common to all organized beings, to act from the 
centre towards the periphery, to expend the matter, to work it for its own purpose, 
and model it according to its ow r n wants and its own design. 
