376 B. F. KINGSBURY 



The development of the cat's ovary, according to my interpre- 

 tation, affords no support for the view that the ovary proper is 

 superimposed as a distinct growth on a vestigial testis represented 

 by the rete ovarii and the medullary cords. The latter, while 

 they present a superficial resemblance, histologically, particularly 

 to the tubules of a cryptorchid testis, are nevertheless obvious- 

 ly ovarian. Their apparent testicular character is due to their 

 form of growth. They contain ova and form follicles, while their 

 cells clearly agree with the follicle cells in structure, and this is 

 also clearly due to the processes occurring within them, which are 

 themselves in part a function of their relations. There remains 

 the fact of the existence of a rete ovarii, the undoubted homolog 

 of the rete testis, particularlj^ well developed in some animals, 

 such as the cat, and connected with some of the so-called medul- 

 lary cords which thus would appear clearly homologous with the 

 tubuli contorti of the testis. The apparent dual structure of the 

 ovary is but a part of the larger problem of the double develop- 

 ment of the internal organs of reproduction in typical vertebrates, 

 referred to at the beginning of the paper. The development of 

 a rete and its connection with the parenchyma of the gonad in 

 the female is but part of the tendency to develop the duct system 

 of the male. The conclusions to which one is almost inevitable 

 compelled is that of a deep-seated hermaphroditic tendency in 

 the development of vertebrates, which finds expression in thfe 

 double character of certain definite organs and structures. This but 

 describes the morphogenetic pattern with a suggestion of its phy- 

 logenetic origin. Upon the analytical side, it might be affirmed 

 that processes determining both male and female duct systems 

 were present in development of each sex. If it were believed to 

 put the problem on a better basis, it might be said that each sex 

 is .heterozygous in this respect, the factors determining the devel- 

 opment of the male duct system becoming dominant in the course 

 of development of the male and vice versa. The development 

 of the ovary indicates strongly that the development and double 

 character of the reproductive system must be clearly differen- 

 tiated from that of sex itself. The development of the reproduc- 

 tive system is double — has two aspects: the establishment of the 



