1 60 MUNSON. [Vol. XV. 



is extremely variable. As a rule, it is spherical ; but it may 

 be perforated with holes and cavities. The center is often 

 finely granular (PI. XIII, Fig. 7). These granules may con- 

 stitute the entire nucleolus, except a thin outer homogeneous 

 membrane (PI. XIII, Fig. 6). 



Then again the center may be occupied by a relatively small, 

 spherical, strongly refractive body, the outer zone being rela- 

 tively uniform in thickness. Occasionally, this outer zone, 

 surrounding the central body, is seen to be radially striated. 

 The striae appear to be continuous with the network of the 

 germinal vesicle. 



Instead of a central body, there may be a central cavity in 

 which nothing stainable appears to exist (PI. XIII, Fig. 5). 

 More frequently, however, the central cavity is filled with a net- 

 work resembling the network of the germinal vesicle, except- 

 ing that the meshes are finer (PI. XIII, Fig. i ; PI. XVI, 

 Fig. 107). As in the latter case, the fibers of the network are 

 more or less covered with stainable granules, and the meshes 

 between these fibers remain unstained. This caving in of the 

 interior, so to speak, appears at times to continue till the 

 nucleolus is nothing but a thin hollow shell (PL XIII, Fig. 6). 

 This shell may be so large as to occupy nearly one-half of the 

 germinal vesicle. Such cases, however, are not frequent. 

 The interior of such a nucleolus is occupied by a chromatin 

 network which in every way resembles the chromatin network 

 of the germinal vesicle. 



More frequently, in this stage of the egg, the nucleolus may 

 be seen to have preserved a solid constitution even to the time 

 when the germinal vesicle has reached the periphery. In most 

 cases it is comparatively large, and stains more intensely than 

 the rest of the germinal vesicle. Yet it is often completely 

 honeycombed with little vacuoles. It often appears as if these 

 vacuoles enlarge and flow together. The large nucleolus then 

 appears like a system of variously connected, stainable strands 

 of nucleolar substance, in appearance not unlike a coarse sponge. 



In rare cases such a large, degenerated nucleolus is accom- 

 panied by another very much smaller, which does not show the 

 signs of degeneration so conspicuously. 



