112 H. H. NEWMAN. 



VI. DEVELOPMENT OF THE OVOCYTE WITH ESPECIAL REFERENCE 



TO VlTELLOGENESIS AND THE COMPARATIVE RATE OF 



GROWTH OF NUCLEUS AND CYTOPLASM. 



The ovocytes in primordial follicles (stage i) are comparatively 

 small cells with homogeneous cytoplasm and large nuclei, the 

 average diameter of ten typical cells being .033 mm. and that of 

 their nuclei .015 mm. At the beginning of the growth period 

 then the cell diameter is only about twice that of the nucleus. 



Soon after the formation of the primordial follicle, before any 

 marked growth of the cell has occurred, distinct spherules of 

 fatty material are distinctly visible in preparations fixed in 10 

 per cent, formalin and stained in Sudan III. Evidently yolk 

 metabolism has begun at this stage. These spherules are so 

 brightly stained with the Sudan that no other interpretation of 

 their character is admissible. They appear excentrically, being 

 confined to one side of the nucleus, thus indicating an early cell 

 polarity. The average diameter of such ovocytes is about .35 

 mm. and that of their nuclei about .17 mm. The proportionate 

 size of cell and nucleus, therefore, has not been materially altered. 

 Such a cell is shown in Fig. 14, which was drawn from an ovocyte 

 somewhat below the average in size, occupying a follicle in a 

 condition between stages I and 2. 



The changes in the ovocyte as found during follicular stages 2, 

 3 and 4 culminate in a condition shown in Fig. 15, where the cell 

 is frequently elongated, showing polarity and bilaterality. The 

 yolk spherules are very distinct and abundant and are confined 

 to the pole opposite to that occupied by the nucleus. The 

 average largest diameter of such cells is about .08 mm. and that 

 of their nuclei about .025 mm. It will be noted that the cyto- 

 plasmic mass has increased relatively much more rapidly than 

 has that of the nucleus, although the latter has doubled its 

 diameter and increased its mass several times. The zona 

 pelucida is present as a comparatively thin but dense layer, which 

 shows evidences of having been laid down as a mesh-work of 

 fibrous material secreted by the basal portions of the follicle cells. 



During follicular stages 5, 6 and 7 a curious change occurs in 

 connection with the process of vitellogenesis. There is a gradual 



