1 98 MUNSON. [Vol. XV. 



structure, greatly obscuring the latter, and causing the whole 

 body to appear very conspicuous as a homogeneous solid body 

 (Fig. 40). On the other hand, it may spread out in a circle 

 surrounding the germinal vesicle (Fig. 48), and even become 

 extended towards the point of attachment of the egg (PL XIII, 

 Fig. 16). In that way it appears to form a channel by which 

 food material is conveyed into the egg. In the vicinity of the 

 germinal vesicle the food material is acted upon, or at least 

 comes in contact with a clear fluid, perhaps karyolymph or 

 nuclear sap, and becomes converted into conspicuous stainable 

 granules. The metaplasm then, instead of collecting around 

 the central structure, may move out into the cytoplasm, caus- 

 ing the fibers of the crescent to expand into the general cyto- 

 plasm ; and the food granules surrounding the germinal vesicle 

 may likewise be variously distributed, causing the inner zone 

 surrounding the germinal vesicle either to entirely disappear or 

 else to become hyaline and devoid of granules (PI. XIV, Figs. 

 19, 24). 



The variable disposition of these three elements — the cyto- 

 lymph, as it may be called, the food granules, and the meta- 

 plasm — appears to be responsible for many of the variations, 

 not only in the position, but also in the form of the vitelline- 

 body. The position of the metaplasm with reference to this 

 body appears to determine the direction of growth. If the 

 metaplasm surrounds the central structure uniformly, the 

 cytoplasm increases uniformly, and the body thus becomes 

 gradually removed from the germinal vesicle. On the other 

 hand, if the central structure lies close to the germinal vesicle, 

 and the metaplasm on the distal side, the cytoplasm appears to 

 increase in the direction of greatest amount of metaplasm ; 

 and if the metaplasm is wholly absent from the structure, as 

 often appears to be the case (Figs. 50, 51, 55), the structure 

 most frequently is found, even in later stages of the egg, to 

 occupy the position which it formerly had (PI. XVI, Fig. 104). 

 In the absence of the metaplasm from the vicinity of the cen- 

 tral structure, this latter does not appear as a conspicuous 

 massive body, but as a fibrous framework of radial fibers with 

 its refractive body in the center (PI. XIV, Fig. 54). 



