SUPPLEMENTARY NOTES ON TWINS IN CATTLE. 



63 



abled me to distinguish the sexes with certainty as early as 3 cm. 

 greatest length. They were then readily diagnosed as male and 

 female, respectively, in their external characters. They were care- 

 fully studied and compared with normals, with the result that the 

 reproductive system of the female was found to be already defi- 

 nitely modified in the characteristics about to be described. 



Fig. 6 shows the external organs of the free-martin. The short 



Fig. 6. Free-martin 3.75 cm. greatest length; Case No. 62. X 6. 1. Um- 

 bilical cord; 2. Teats; 3. Phallus. 4. Homologue of scrotal sac of male, 

 formed in all females; 5. Urinogenital aperture; 6. Anus. 



length of the perineum and the development of the urinogenital 

 aperture are distinctive female characteristics. In the male the 

 perineum is several times longer and marked by a ridge; there is 

 no urinogenital aperture in the male, and the phallus is placed more 

 anteriorly with reference to the scrotal sacs, which are entirely 

 similar in the two sexes. 



Figs. 7, 8, and 9 show the internal urinogenital organs of the 

 free-martin (Fig. 7), of its male twin (Fig. 8), and of a normal 

 female 3.6 cm. greatest length (Fig. 9). These figures are drawn 



