§ 2 HISTOGENESIS OF CORPORA LUTEA 87 



cytosis of the egg contents by the granulosa cells, accompanied 

 by marked increase in the size of the cells. 



b. The f^-stage. This stage is characterized by the con- 

 version of the substances within the cells, and its absorption 

 by the blood. When the cell in question has taken up a certain 

 amount of ovular substance, the basally-situated cell shifts 

 towards the apex, in such a way that the nucleus (much like 

 the piston of a pump) rises along the cell- wall, thus dividing 

 the high cylindrical cell into two separate parts (Fig. 66a), 

 which differ from each other in structure. The apical cell- 

 space still contains the phagocytosed ovular substances in the 

 form of granules, and also some yolk. In the basal cell-space, 

 on the contrary, a small vacuole may at first be observed, 

 filled with a homogeneously coloured, often finely- 

 granulated substance, whose chemical and physical behaviour 

 differs from that of the apical ovular material. The quantities 

 of material respectively taken up apically and accumulated 

 basally are inversely proportional ; the larger the basal vacuole, 

 the smaller the amount of apically admitted material we shall 

 find, and the higher the nucleus will be, until at last the 

 latter is able to reach the apex. Often the granulosa cell is 

 completely filled by a large basal vacuole, for which reason 

 we have provisionally called it a "vacuole cell (Fig. 66a). 



Simultaneously with this conversion of substances within 

 the vacuole cells a rapid cellular division takes place among 

 the granulosa cells. Only rarely are mitoses found; amitotic 

 division of nuclei, on the other hand, occurs very frequently. 

 After the division of the nucleus, part of the cytoplasm may 

 be seen to split off, with one of the nuclear parts, from the 

 mother-cell. This causes the granulosa layer to increase rapidly 

 in thickness (Fig. 66). 



Further, these daughter-cells often become free and invade 

 the follicular space (Fig. 66). Both in the mother-cell and in 

 the daughter-cells the incorporation of yolk continues. 

 Further division occurs in those daughter-cells which have 

 invaded the follicular space; they are often found joined to 

 form long strands, or they may form small syncytia with 

 several nuclei (Fig. 66). 



