A MICROSCOPIC STUDY OF THE REPRODUCTIVE 

 SYSTEM OF FOETAL FREE-MARTINS 



CATHARINE LINES CHAPIN 



Hull Zoological Laboratory, University of Chicago 



SIXTEEN FIGURES 



The following study of one phase of the free-martin problem 

 was suggested to me by Prof. F. R. Lillie and has been pursued 

 under his direction. To him my thanks are due for his kindly 

 advice and constructive, criticism. 



The foetal free-martins used in this investigation are those 

 described by Professor Lillie in the preceding paper (this Jour- 

 nal, p. 371 to 452). Some of these specimens w^ere preserved 

 in toto in 5 per cent formalin. Other specimens were dissected 

 as soon as possible after being brought to the laboratory and 

 parts to be used for histological study were preserved in Zenker's 

 fluid or in strong Flemming solution. The gonads and related 

 organs, including in most cases the Wolffian body and the Wolf- 

 fian and Miillerian ducts, of the foetal free-martins were sec- 

 tioned. These organs were studied also in normal males and 

 females of approximately the same size as the free-martins. 



Two series of records of specimens were kept ; one, of the series 

 of twins described in the preceding paper and one, of the series 

 of normal embryos collected to study in comparison with the 

 free-martins found in the twin series. Individuals of the twin 

 series, which includes twins of both the one sexed and the tw^o 

 sexed types are designated by the letter T and their serial num- 

 ber; individuals of the normal series are designated by N and 

 their serial number. Histological preparations were made from 

 some of the normal males and females for comparison with the 

 free-martin. There is no indication in the early stages studied 

 that, at a given degree of development, there is any marked dif- 

 ference in size between a single embryo and a twin. Thus a 



453 



THE JOUnXAL OF EXPERIMENTAL ZOOLOGY, VOL. 23, NO. 2 



