MORPHOGENESIS OF THE MAMMALIAN OVARY 359 



fatty ('lipoid') nature were found in the medullary cords of the 

 95 mm. and 112 mm. fetus, three to four-day kitten, and still 

 demonstrable in the six-day kitten. They may have been pres- 

 ent in the earlier stages examined, but the technique was not of 

 a nature to demonstrate their presence easily, von Winiwarter 

 and Sainmont found the fat globules appearing about forty-five 

 days p.c. (i.e., 70 mm. length, Sainmont), and no longer present 

 three days p.p. They reject the interpretation of Allen ('04) in 

 the pig, that the presence of fat is indicative of degeneration of 

 the medullary cords. They emphasize on the contrary the pres- 

 ence of fat as evidence of profound metabolic change taking place 

 in the medullary cords at this time. This, perhaps, could hardly 

 be questioned. It might be added, however, that one can hardly 

 speak of a "disappearance of lipoid from the medullary cords," since 

 the application of what I may term a 'mitochondrial technique' 

 adduces evidence of the presence of fat in abundance in masked 

 form in all the epithelial cells within the ovary — so-called medul- 

 lary cords, follicle cells and ova — at all stages of their later 

 growth, at least, appearing as free hpoid globules in the last, in the 

 process of their vitellogenesis. Hence the question resolves itself 

 into the reason for the existence of droplets of free lipoid in the 

 epithelial cells (medullary cords) in the deeper portions of the 

 ovaries. Inasmuch as I find evidence of dwindling and disap- 

 pearance of these cell cords in the deeper portions of the ovary 

 at about this time (after birth) I incline to the interpretation 

 offered by Allen. 



The 'large cells' present in the medullary cords and the surface 

 epithelium have not been specially studied by me. The}'- were 

 encountered in the two youngest embryos and in the surface 

 epithelium, particularly in the zone bordering the hilum, well 

 along in postpartum stages. I have seen no reason for drawing 

 a sharp line between these cells and obvious 'germ cells,' as I 

 believe that all intergradations between them and the latter may 

 be found. On the other hand, most of them, at least in the ante- 

 partum ovary, do not give rise to the definitive germ cells of 

 the adult ovary, and hence are not primordial germ cells in the 

 original sense ('Ureier,' of Waldeyer). It is unnecessary to 



