368 



Fig. 2. Transverse Section of the end of the ovary of No. 7 (x: about 40). 

 Near the middle, a very early stage of the forming corpus luteum appears. It 

 shows quite clearly the coagulum and also the irruptions of the theca folliculi which 

 tend to divide the corpus luteum into lobules but have not yet completely grown 

 through the membrana granulosa. On either side of this and adjacent to it are 

 2 nearly ripe biovular follicles. One of these clearly indicates that the 2 ova, one 

 of which contains a nucleus, are practically equally developed and both of them have 

 the zonae of the two ova in contact for a considerable part of their circumference. 



Fig. 3. Transverse Section of a corpus luteum at the end of the period of 

 formation from No. 9 (X about 60). The enormously hypertrophied cells of the 

 membrana granulosa are seen forming the characteristic lutein cells among which 

 the thecal ingrowths are forming an anatomosing network. The centre of the corpus 

 luteum is filled by a plug of the thecal cells. In older corpora lutea the size of 

 tliis central plug is reduced. 



Fig. 4. Transverse Section of part of the two adjacent corpora lutea from 

 No. 9 (X about 175). This shows one of the thecal irruptions in the base of which 

 are three small blood vessels. To the left of the ingrowth the membrana propria 

 is still pfesent, but no trace of it is to be seen abround the ingrowth itself. 



Fig. 5. Transverse Section of a follicle in one of the ovaries of No. 15 

 (X about 42). The ovum with a peripherally situated nucleus is seen surrounded 

 by the zona peUucida. The cells of the membrana granulosa have increased and 

 almost filled the cavity of the follicle and although they are partially transformed 

 into luteal cells there is no indication of any thecal ii'ruptions. 



Plate XL 



Fig. 6. Two transverse Sections of two contiguous primordial ova in one 

 follicle from A (X about .390). Each ovum shows the nucleus with its nucleolus 

 and nuclear membrane. The zona peUucida has not yet formed so that the two 

 ova are actually in contact along the middle line. They are surrounded by epithelial 

 cells, the forerunners of the membrana granulosa, but have no conjunctive theca. 



Fig. 7. Transverse Section of two ordinary primordial ova fiom A (X about 

 390). These are similar in structure to those in fig. 6, but they are clearly separated 

 one from the other by the primitive membrana granulosa cells. 



Fig. 8. Transverse Section of two contiguous primordial ova in one follicle 

 from A (x about 390). They are slightly older than those in fig, 6. The zona 

 peUucida has commenced to form and is seen separating the two ova, but there is 

 no indication that the cells of the membrana granulosa have penetrated between 

 them. The epithelial cells form a definite unicellular layer and the membrana pro- 

 pria is just forming. 



Fig. 9. Transverse Section of a nearly ripe biovular follicle from A (X about 

 45). The follicle has a large cavity containing liquor folliculi. The membrana 

 granulosa is reduced to a fairly thin layer and the discus proligerus is attached to 

 it by the letinacula. The two ova, one of which is slightly crumpled up, are each 

 surrounded by a well marked zona and are closely apposed to one another. 



Fig. 10. Transverse Section of a polyovular follicle containing three ova 

 from B (X about 100). The nuclei of two of the ova are shown, that of the remaining 

 ovum occurs in another section. The ova are in a much more advanced condition 

 than in figs. 6—8 and are closely apposed. 



Figs. 11 and 12. Two consecutive Transverse Sections of polyovular follicles 

 containing 4 and 5 ova from B (X about 78). These are still more advanced than 

 those in fig. 10. The follicle on the right shows the nuclei of four out of its five 

 ova, that on the left however only shows a nucleus in one of its four ova, the other 

 nuclei occurring in different sections. The eggs are practically developed and it 

 will be noticed that in some of them quite a large part of the zona is apposed to 

 that of the other ova and so removed from membrana granulosa. 



