I I -I- H. H. NEWMAN. 



other mammals the name "zona radiata." The cell is now 

 over four times as great in diameter as the nucleus and there is 

 little further alteration in their relative masses until after the 

 rupture of the membrane of the germinal vesicle when the first 

 maturation spindle is established. 



During the stages of follicular development numbered 8, 9 

 and 10 there occurs a gradual reorganization of the cytoplasmic 

 materials of the ovocyte. A zone of denser homogeneous proto- 

 plasm comes to occupy a peripheral position, forming an in- 

 creasingly more and more sharply defined cortex, somewhat 

 thickened at the point where the nucleus is flattened against 

 the cell membrane. In the center of the ovocyte the protoplasm 

 has assumed the character of a very coarse alveolar mass in the 

 meshes of w r hich are rather large irregular solid bodies which 

 stain with Sudan III. The alveolar structure, which is seen in 

 sections of material fixed in neutral formalin, assumes in paraffin 

 sections the appearance of a fluid core in which are suspended 

 scattered strands of deeply staining fibrous material and a central 

 irregular mass of large solid pieces of irregular size and form. 

 Such a condition finds its exact counterpart in Dasyurus (see 

 Hill, '10, Fig. i), and is characteristic of the same stages of 

 follicular development. The condition at the time when the 

 clearest definition is established between the two cytoplasmic 

 zones is shown in Fig. 17. Here the "formative zone" (/.2.) 

 is shown as a somewhat thicker cortical layer than is usually 

 found, an*d the deutoplasmic mass (d.z.} is represented as coarsely 

 alveolar, a structure which it appears to have when seen in 

 formalin preparations. It will be noted that the nucleus occupies 

 a position in the middle of the thickest part of the formative 

 cortex, a position which probably represents the animal pole of 

 the ovocyte. The diameter of the cell at this stage is on the 

 average about .12 mm., while that of the nucleus has not changed 

 since the stage represented in Fig. 15. The ovocyte is now full 

 grown and ready for the changes incidental to the maturation 

 processes. 



During maturation a very radical change in the cytoplasmic 

 structure of the ovocyte takes place. The comparatively 

 homogeneous formative zone of the full-grown ovocyte has 



