294 KANSAS UNIVERSITY SCIENCE BULLETIN. 



disks which do not stain, but lie bright and shining, refracting 

 the light to a much greater degree than the surrounding struc- 

 tures. (Fig. 20, pi. XIV.) 



c. The Vitelline body. 



Up to the time when the oocyte has left the ovarian sac, there 

 is no trace of a vitelline-body ; but the earliest follicular eggs 

 contain what I take for the beginning of its formation. ( Fig. 1, 

 ^, pi. XII.) Close against the nuclear membrane, and atone side, 

 granules begin to collect, as if the cytoplasm were condensing at 

 this point. The mass is at first scanty and extends only par- 

 tially around the nucleus, forming a thin, crescent-shaped body ; 

 the granules are now very coarse and far apart. But as the 

 crescent widens or increases in size the granules aggregate more 

 closely, becoming quite dense at the point near the nuclear 

 membrane where they first collected. Before this zone of dark 

 granules has extended entirely around the nucleus, careful 

 focusing will show a small sphere at its densest point. ( Fig. 

 10, a, pi. XIII.) This appears to be a simple capsule ; at least 

 there are no concentric la)'^ers as seen later. I am not certain 

 of the internal structure of the body at this early age, but it 

 is probably even at this time more complex than it appears, as 

 I was able later, when the surrounding granules are less 

 dense, to make out definite granules within. The usual ap- 

 pearance, however, and especially in its early stages, is a clear 

 sphere, with a thin but well-defined surrounding membrane. 



The crescent increases in size until its horns often meet on the 

 opposite side of the nucleus (Fig. 11, pi. XIII.) This indicates 

 an increasing amount of the granular deposit, which is doubtless 

 a food material. As the mass thickens it forms into layers 

 around the central sphere, the layers varying in number, width, 

 and density. The number indicates to some extent the age of 

 the body, the larger and consequently the older eggs having a 

 greater number of rings than the smaller. ( Fig. 12, pi. XIII.) 



Fixations and stains have much to do with the appearance 

 of the vitelline body ; some obscure the concentric layers com- 

 pletely and cause the structure to Icok like a homogeneous 

 mass. (PI. XII, fig. 9.) Often, however, in the best-stained 

 material the body varies, and I am inclined to believe that 

 variations in appearance are not always due to stains and fixa- 



