54 H. H. NEWMAN. 



The full grown ovocyte of the armadillo has the structure 

 shown in text-figure I. The cytoplasm shows two clearly defined 

 regions, a peripheral zone of deeply staining homogeneous proto- 

 plasm, the formative zone (f.z.~), and a central lightly staining, 

 spherical mass of coarsely reticular or alveolar material, the 

 deutoplasmic zone (d.z.), in which occur irregular masses of 

 coarse and deeply staining granules (d.g.), the supposed equiva- 

 lent of the yolk or deutoplasmic granules of the ova of marsupials. 

 The germinal vesicle (g.v.} is flattened against the dense zona 

 pelucida (z.p.} at the animal pole and in it the chromatin is seen 

 as tetrads or in other forms characteristic of the prophases of 

 maturation. Such an ovum has the appearance of being centro- 

 lecithal. Coincident with the formation of the first maturation 

 spindle a radical rearrangement of the two cytoplasmic zones 

 occurs. The deutoplasmic sphere pushes its way to the surface 

 at the animal pole and crowds the formative material to the 

 vegetative pole where it assumes the form of a cap, thick at the 

 pole and thinning out to a feather edge at the equator (see text- 

 figure 2). The polar spindle, in a stable metaphase (p.s.), 

 occupies a position as near the animal pole as possible without 

 leaving the formative material and has its axis tangential to the 

 periphery of the ovocyte though parallel with that of the main 

 axis of the cell. This spindle is evidently insulated from the 

 surrounding formative protoplasm by a capsule of non-staining 

 material, and has no astral rays. 



A very large number of ovocytes were found in exactly this 

 condition and it seems certain that the progressive changes 

 normally come to a standstill at this point. The next step in 

 normal development is ovulation, the stimulus of which initiates 

 the completion of the maturation process. Such resting ovo- 

 cytes occur in large follicles whose granulosa cells are intact and 

 whose follicular fluid is homogeneous, abundant, and stains deeply 

 with haematoxylin and allied stains. In any normal ovary during 

 the period of cestus there are many ovocytes of this sort, all in 

 practically the same condition and equally ready for ovulation. 

 Probably such mechanical factors as size of follicle or nearness 

 to the periphery determine which follicle shall rupture first. 

 Fertilization of this one egg seals the fate of all the remaining 



