THE OVUM OF THE XIXE-BAXDED ARMADILLO. 



disappearance of the yolk spherules (which earlier constituted 

 such a marked feature of the cytoplasm) culminating in the con- 

 dition shown in Fig. 16, in which the protoplasm of the ovocyte has 

 acquired a secondary homogeneous structure, with a coarsely 

 alveolar appearance. There are present scarcely any discrete 

 fatty particles, but the whole cytoplasmic mass assumes a 



FIG. 13. A primordial ovocyte (X4io). 



FIG. 14. An ovocyte at the time when an epithelial follicle has just been estab- 

 lished. Note the presence of yolk granules (X4io). 



FIG. 15. A half-grown ovocyte, showing a characteristic elongated shape and 

 the presence of numerous yolk granules (X4io). 



FIG. 16. An ovocyte practically full grown, in the so-called "pseudoalveolar" 

 stage. Note that the yolk granules have almost entirely disappeared (X4io). 



pinkish tint when subjected to Sudan III, a circumstance that 

 would seem to indicate the presence of fatty materials in solution. 

 Such a stage is evidently equivalent to that seen in Dasyurns and 

 designated by Hill as the "pseudo-alveolar" stage (compare Hill, 

 '10, Fig. 4); It will be noted that the nucleus is drawing closer 

 to the periphery and has reached its maximum size, with a 

 largest diameter of about .025 mm. and always somewhat 

 flattened in form. The diameter of ovocytes of this type averages 

 about .1 mm. The zona has attained its definitive thickness of 

 .003 mm. and is a dense membrane showing no radiations like 

 those which have given to the homologue of this structure in 



