TWINNING IN DASYPUS NOVEMCINCTUS 33 



gv 



(immature eggs) develops its own separate follicle, and 



the development of both ovocyte and follicle is much 



like that of the mouse or the cat. In only a very few 



instances has a foUicle with two or more ovocytes been 



observed, and many ovaries totally lack double or 



multiple follicles. The full-grown ovocyte, which has 



a diameter of about 12 micra, is a little smaller than 



that of the cat and a Httle larger than that of man 



or those of rodents. 



Prior to maturation 



the definitive ovocyte 



of the first order lies 



in the discus pro- 



ligerus, a mass of 



follicular cells, which 



adheres to one side 



of the large follicular 



cavity. 



A cytological ex- 

 amination of the 

 full-grown ovocyte 

 (Fig. 5) shows that 

 there exists a pro- 

 nounced cellular 

 polarity. The germinal vesicle is flattened against the 

 zona pellucida presumably at the animal pole. A 

 comparatively homogeneous zone of darkly staining 

 protoplasm which is thicker at the pole occupied by 

 the germinal vesicle surrounds a sphere of coarsely 

 vacuolated material, which must be identilied as the 

 deutoplasmic zone or yolk mass, in which are scattered 

 bits of yolk material suspended in a fluid medium. 





Fig. 5. — Full-grown ovocyte (un- 

 maturated egg) of the armadillo, showing 

 the mass of thin yolk in the center {d s) 

 and the peripheral formative zone of 

 protoplasm (/s), the nucleus or germinal 

 vesicle {g v) at the animal pole, and the 

 zona pelucida or egg shell {z p). 



