BANCROFT: OVOGENESIS IN DISTAPLIA OCCIDENTALIS. 103 



and for some time later, they are the only structures in the nucleus that 

 take a decided chromatic stain. 



After further increase in size, haematoxylin stains the cortex deeper 

 and deeper, until it is barely possible to see the medulla and the 

 refractive bodies (Plate 6, Fig. 56). Later this deep staining is 

 still more pronounced, so that both medulla and refractive bodies are 

 entirely obscured and only a faint lighter central area perceived (Plate 

 6, Fig. 48). During the earlier stages also iron haematoxylin usually 

 stains the nucleolus so strongly that no structure can be detected within 

 it; and only exceptionally are the conditions illustrated in Figures 51 

 to 56 (Plate 6) to be made out. In such instances, however, they 

 may be brought out most distinctly. But with methyl green and acid 

 fuchsin, medulla and cortex are usually differentiated, though not so 

 clearly as with a favorable haematoxylin stain. 



For the further history of the nucleolus I have depended almost 

 entirely upon the methyl green and acid fuchsin combination. All of 

 the structures increase in volume, the refractive bodies probably most 

 rapidly, until at the time when the yolk bodies are being formed some 

 are considerably over 1 fx in diameter. They still stain a bright green, 

 and are very refractive, but the largest are no longer homogeneous, ap- 

 pearing to be filled with many refractive granules (Plate 6, Fig. 58). 

 Though usually located in the medulla, some are occasionally found 

 within the cortex (Fig. 58). The cortex itself appears perfectly 

 homogeneous, while the medulla is finely granular, but both take the 

 same bluish tint. The medulla is no longer spherical, but flattened on 

 one side. 



From now on, while the germinative vesicle is shrinking, and after 

 the yolk is formed, both cortex and medulla take a fainter and fainter 

 stain, until finally they can no longer be distinguished with the use 

 of this stain. During this process they usually are of a diff'use green 

 color, and sometimes the vicinity of the refractive bodies, which remain 

 with unimpaired distinctness, has a faint suffusion of green, which is 

 probably an indication of the presence of what is left of the nucleolus, 

 though its outlines cannot be seen. After the central yolk clump 

 has broken up, this stain has never shown anything of the nucleolus 

 except the refractive bodies; but I think that the other portions are 

 still there, for in the occasional well-stained haematoxylin preparations 

 of this stage it is still seen (Plate 6, Fig. 50), though in this case 

 too it is fainter than in the stages immediately preceding. 



In addition to the stains already mentioned, I also tried List's 



