THE STRUCTURE OF FREE-MARTIN GONADS 65 



that primarily the gonad is female in structure and that second- 

 arily it is transformed into a male gonad by hormonic action. 



Since the embryological evidence is alone the key to the cor- 

 rect explanation, it is the purpose of the present account to 

 interpret the microscopic structure of the post-natal gonad on the 

 basis of its development. The facts presented in this paper were 

 gathered in a study of the gonads of seven foetal free-martins 

 (Miss Chapin's material) ranging in length from 7.5 cm. to 28 

 cm., and from nine post-natal free-martins ranging in age from 

 five days to three years. Data obtained from a study of the 

 gonads of normal males and females of approximately the same 

 sizes and ages are introduced for comparison. For complete 

 lists of the specimens and tabulated summaries of the micro- 

 scopical findings, tables 1, 2, and 3 may be consulted. A list 

 of the foetal free-martin gonads studied is given in Miss Chapin's 

 tabulated summary (Chapin, '17, p. 478). 



We are deeply indebted to Prof. Leon J. Cole, of the Univer- 

 sity of Wisconsin, for the reproductive glands from the following 

 post-natal free-martins: H-18, H-46, H-36, H-37, H-42, and H-40 

 of table 1, for the use of the manuscript, "The anatomy of the 

 urino-genital system of the free-martin," prepared by his stu- 

 dent, Mr. J. V. Seids, and for other data not contained in the 

 manuscript. Without these the present work would have been 

 impossible. The remaining specimens are from Professor Lillie's 

 collection. Different fixing agents were employed, the more 

 common ones being formahn, Zenker-acetic, strong Fleming's 

 solution, and Bouin's solution, Heidenhain's iron hematoxylin 

 and Mallory's triple stain were the stains most commonly 

 used. 



The study of this problem was undertaken at the suggestion 

 of Prof. Frank R. Lillie, and it gives me great pleasure to acknowl- 

 edge my deep indebtedness to him for instruction and for kindly 

 advice. 



