THE MORPHOGENESIS OF THE MAMMALIAN OVARY: 

 FELIS DOMESTICA 



B. F. KINGSBURY 



Department of Histology and Embryology, Cornell University 



THIRTY-TWO FIGURES 



It is a striking peculiarity in the development of the reproduc- 

 tive system in man and mammals (not to consider other forms of 

 the Vertebrata) that the duct system (modified in the female) is 

 laid down double, the duct system of the male disappearing in the 

 female or persisting as vestigial structures and vice versa, the 

 organs of the female duct system and the mammary gland being 

 vestigial in the male. The embryo in the course of development 

 thus passes through an indifferent period during which the sex can- 

 not be ascertained, followed by the period of sexual differentiation. 

 In the double appearance of the reproductive fundaments devel- 

 opment is protandrous — that is, the 'male' system appears earlier 

 than the female — this rule applying also to the differential devel- 

 opment of the ovary and the testis as well as the duct system. 

 No fully satisfactory explanation has been given for this double 

 development in the internal reproductive system. Three or 

 four general explanations have been offered for this fundamental 

 law. (1) The primitive vertebrate was hermaphroditic and that 

 even in the higher forms the hermaphroditic tendency persists 

 showing itself in the development of a double system, male and 

 female, even causing the development in the male of a rudimentary 

 mammary gland, in the female of a rudimentary prostate gland — 

 organs which did not extend back in the line of vertebrate de- 

 scent anywhere near the hypothetical hermaphroditic ancestral 

 form. The occurrence of hermaphroditism among the ascidians 

 and lower vertebrates (that is, Myxine) and the sporadic appear- 

 ance of a true or false, complete or incomplete, hermaphroditism 



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