THE EMBRYONIC DEVELOPMENT OF THE OVARY 

 AND TESTIS OF THE MAMMALIA. (PRELIM- 

 INARY ACCOUNT.) 



BENNET M. ALLEN. 



The following is a preliminary account of work begun in the 

 spring of 1900, upon the subject of the development of the ovary 

 and testis of the mammalia. The rabbit and pig have served as 

 the subjects for this work. The results will here be very briefly 

 set forth, a more detailed account being reserved for a later paper. 

 The material studied includes various stages in the development 

 of the ovary and testis of the rabbit, from the thirteen-day embryo 

 to and including adult stages. The pig material includes only 

 embryonic stages, but is more complete for the period covered 

 than is the rabbit material. 



The work was carried on with the aim of solving the following 

 problems: (i) the origin and development of the seminiferous 

 tubules and their homologues in the ovary ; (2) the origin, devel- 

 opment, and homologies of the rete tubules, also their relations to 

 the Malpighian corpuscles of the mesonephros on the one hand, 

 and to the seminiferous tubules of the testis and medullary cords 

 of the ovary on the other ; (3) the origin, development and 

 homologies of the connective tissue elements and interstitial cells 

 of the ovary and testis. 



Incidental to the solution of these problems, the work has in- 

 volved to a greater or less extent, a consideration of the follow- 

 ing allied problems: (i) the development of sex cells; (2) the 

 morphological phases of sex differentiation ; (3) cell degenera- 

 tion in the sex gland and rete region, (4) the degeneration of 

 the mesonephros, and the development of the Wolffian and Miil- 

 lerian ducts. 



The results of work in so large a field can be, only to a limited 

 extent, new. Certain of the following results are confirmatory of 

 the work of other authors, to whose results I shall refer in a 

 later paper. The very contradictory opinions met with in the 

 literature on the subject call for confirmatory evidence upon these 

 problems. 



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