CHAPTER X 

 SUMMARY AND RECAPITULATION 



For the purposes of this monograph an ovum is considered 

 as such from the moment of its functional differentiation in 

 the ovary until its implantation in the uterine endometrium. 

 An examination has been made of the experimental investi- 

 gations of the growth and development of the mammahan 

 ovum during the various stages of its life history in the 

 ovary and oviducts. 



The problem of the origin of the definitive ova has re- 

 ceived much attention, but it cannot be said to have been 

 completely resolved. If we are to judge by evidence from 

 non-mammalian forms the large amoeboid primordial germ 

 cells must enter the embryonic gonad if it is to differentiate 

 as a functional organ. A functional ovary develops only 

 from embryonic gonads in which the secondary sex cords 

 proliferate to form a true ovarian cortex associated with the 

 germinal epithelium. 



The ovaries of young mammals contain large numbers of 

 primitive oocytes. The conception that these oocytes are 

 the only precursors of the definitive ova is controverted by 

 a large body of recent evidence which indicates that new 

 ova are .proliferated from the germinal epithelium and that 

 the rate of this proliferation varies with the various stages 

 of the oestrus and pregnancy cycles. Ovogenesis in the adult 

 seems to be partially inhibited by certain secretions of the 

 anterior pituitary, the gonad-stimulating hormones affect- 

 ing follicle growth primarily. The exact relation of the 

 gonad-stimulating hormones to the ovogenetic processes is 

 not at all obvious. It seems certain that the prophase 

 stages of the oocyte nuclei occur independent of pituitary 

 hormone activity. 



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