Relation between Nucleolus and Chromosomes. 41 



rather poorly the cell-cytoplasm. Similar combinations of stains were used 

 with the eggs as with the ovaries and yielded similar results. 



EARLY OVARIAN STAGES SYN1ZESIS. 



Among masses of oogonia it is difficult to distinguish definite cell- 

 borders. The cells have comparatively large very chromatic nucleoli, cen- 

 trally situated and enmeshed in a very delicate achromatic (linin) nuclear 

 reticulum (fig. i). The diameter of the nucleus is approximately 2.5 

 microns and that of the nucleolus one-third as much. What cytoplasm 

 could be seen between the cells stained straw-color with orange G. I have 

 been unable to discover a single instance of mitosis among the oogonia 

 either in very young or mature individuals. A stage of slightly larger size 

 (figs. 2, 3) has a faintly chromatic nuclear network and a slightly more 

 definite cell-border. With iron hematoxylin and orange G the nucleolus 

 again stains deep black, while the granular cytoplasm stains blue. This is 

 a typical oocyte of the first order just entering upon its growth-period. 



Among these earliest reproductive cells are frequently seen dark-stain- 

 ing (black with iron hematoxylin and green with Auerbach's stain) bodies 

 of about the size of the nuclei of the smallest oocytes. They are prob- 

 ably degenerating oogonia, now performing the function of "nurse cells." 

 They lie scattered singly or in clumps among the oogonia. Occasionally 

 there is faintly visible around some of these bodies a slight cytoplasmic 

 rim. These chromatic bodies are probably similar to the " nutritive nuclei " 

 described by Griffin in Zirphcra. 



Very conspicuous among these youngest apparently resting oocytes are 

 such as are in more or less close synizesis (McClung) (figs. 6, 7, 8, 9). 

 Usually these stages appear in pairs or quartettes. Such pairs indicate that 

 they are the daughter-cells of primordial germ-cells undergoing synchronous 

 development. The oocytes in synizesis are slightly larger than the youngest 

 oocytes above described. The minute size of the cells makes it difficult to 

 determine with certainty upon definite transition stages leading to the con- 

 traction stage. It is clearly evident that the cells are gaining in volume and 

 I have accordingly adopted as my best criterion of development the size of 

 the nucleus. Proceeding on this basis, I have discovered the following char- 

 acteristics of the transition stages : The cytoplasm continues granular and 

 basic in staining reaction. The nucleolus remains intensely chromatic and 

 usually assumes an eccentric position. The nuclear network gains in chro- 

 matin and becomes progressively more conspicuous, both as to its chromatin 

 and linin elements. The chromatin is largely gathered in clumps along the 

 nuclear membrane (fig. 4). Presently the entire network becomes chromatic 

 and in a slightly later stage assumes the form of a spireme (fig. 5). The 

 threads (probably two in number) then shorten and thicken and contract in a 

 tangled knot about the nucleolus and gradually close up in complete synizesis 

 (fig. 10, size of nucleus 5.0 microns). 



