No. 561] THE NINE-BANDED ARMADILLO 521 



Ovogenesis and Fertilization 

 The early phases of ovogenesis are in no way peculiar 

 and in themselves offer no clue as to the physiology of 

 polyembryonic development. A detailed study of the 

 growth period of the ovocytes and of folliculogenesis 

 shows that in normal ovaries there is only one ovocyte 

 to the follicle and that in ovulation only one egg is given 

 off at a time. The details of maturation are like those of 

 other mammals, especially like those of the marsupial 

 Dasyurus as presented by Hill ( '10). The growth period 

 involves an accumulation of deutoplasmic material, 

 which in the full-grown ovocyte lies in the form of a 

 coarsely vacuolated central sphere containing deeply 

 staining granules. Surrounding the deutoplasmic sphere 

 is a fairly thick peripheral zone of homogeneous proto- 

 plasm, called the formative zone (Fig. 2), which is some- 

 what thicker at the animal pole where the germinal 

 vesicle is flattened against the zona pellucida. During 

 the maturation process a remarkable reorganization of 

 the cytoplasmic regions of the ovocyte occurs. The fluid 

 deutoplasmic sphere forces its way to the surface and 

 comes to lie in contact with the periphery of nearly the 

 whole animal hemisphere of the cell. This forces the 

 formative protoplasm to the vegetative pole where it 

 assumes the form of a cap thick at the pole and thin at 

 the equator, having a crescentic outline in meridional 

 section (Fig. 3). The maturation spindle, forced from its 

 normal position at the animal pole, lies as near the latter 

 as possible without leaving the formative protoplasm, 

 and assumes a position tangential to the nearest periph- 

 ery of the cell, but nearlv parallel to the primary axis of 

 the latter. 



The two maturation divisions occur without disturbing 

 this new arrangement and no other radical change seems 

 to take place until after fertilization, at least so one must 

 conclude from the fact that a tube egg in a late phase 

 of fertilization still shows the formative and deuto- 

 plasmic zones arranged as in Fig. 2. This one fertiliza- 



