152 MUNSON. [Vol. XV. 



egg of the frog. He was unable to state whether this was 

 accompanied by a division of the nucleus. 



Balbiani ('93) found that the ovarian eggs of spiders also 

 degenerate ; and he figures follicles filled with cells. 



I am unable to make any positive statements in regard to 

 the immediate causes of metamorphosis. I believe, however, 

 that the following statement can be made : the cause of the 

 disturbance lies in the egg itself. In the present case there 

 is no true follicle epithelium surrounding the egg. The cells of 

 the stalk, which correspond to the follicle epithelium in other 

 eggs, and which appear to have a similar relation to the egg 

 so far as the function of nutrition is concerned, seem perfectly 

 normal. They often appear to be unusually active and evi- 

 dently enter the egg at the proximal pole (PI. XIV, Fig. 31). 



The conditions which make this possible, as it seems to me, 

 lie in the egg itself, and not in an abnormal condition of the 

 follicle cells, as has been supposed by Flemming ('95) in the 

 case of other eggs. 



The Germinal Vesicle. 



A network can be distinguished quite early in the germinal 

 vesicle, and the stainable substance, losing more and more its 

 definite form, becomes distributed in irregular granules over 

 this network, and also between the meshes, being especially 

 abundant at the nodes. The stainable substance tends to 

 become massed at the periphery, and especially at one point, 

 where the nucleolus early makes its appearance. As the 

 nucleolus increases in size, the remainder of the germinal ves- 

 icle loses more and more its power of staining deeply in car- 

 mine and haemato.xylin, and is no longer capable of being 

 differentiated, as ordinary nuclei are, by means of the green of 

 the Biondi-Ehrlich triple stain. 



During the first stage of the egg the germinal vesicle is 

 spherical and occupies a slightly excentric position when 

 viewed in the plane passing through the centrosome and 

 sphere. In a plane at right angles to this, its position is about 

 central (PI. XIV, Figs. 34, 38-41). 



