MADE AT THE PLYMOUTH LABORATORY. 259 
question whether the radius of the sphere which is determined by 
the presence of the vitelline body has any particular position in the 
subsequent history of the egg will be considered later. 
Tt will appear, then, that the body in question, judging from exa- 
mination of entire fresh ova treated with acetic acid, is not present 
in the youngest ova, but becomes visible when they have reached a 
Fira. 1.—Developing eggs from the ovary of a plaice 83 inches long, examined August 30th, 
1894; treated with dilute acetic acid. Seen with Zeiss E, oc. 3. 
certain definite size; that it makes its appearance in the form of a 
few granules close to the wall of the germinal vesicle, and as the 
egg becomes larger is gradually more and more separated on ae 
latter, at the same time increasing in size and opacity. This 
suggests that the body is formed from the germinal vesicle by the 
expulsion of granules ; but no direct evidence of this can be seen, 
and, moreover, it is not supported by the fact that the vitelline body 
increases in size after it is separated by a layer of protoplasm from 
the germinal vesicle. In eggs in which the yolk has begun to 
appear at the surface of the cell-plasma the vitelline body is seen 
beneath the layer of yolk granules, and it never actually reaches the 
surface of the egg. 
After the character of the vitelline body has been studied in ova 
treated with acetic acid, it is possible sometimes to make it out in 
living ova without the addition of any reagent. It is seen then as 
a group of faint granules whose opacity and refringent power are 
very slightly different from those of the surrounding cell-plasma. 
There is, therefore, a stage in the development of the ova in a 
flat-fish in which neither the vitelline nucleus nor the yolk have 
appeared or commenced to develop. It would be interesting to 
have a satisfactory account of the whole history of the ovum, and 
particularly of this early stage, but at present there are many pas- 
sages in the history not yet elucidated. In prepared sections of an 
