384 FRANK R. LILLIE 



4- Discussion 



The preceding considerations constitute an a;-gument that the 

 free-martin is zygotically female, which may be summarized as 

 follows: 1) The only basis on which it could be logically inter- 

 preted as male is that it is co-zygotic with its male mate, because 

 it is impossible to suppose that the association of two males in 

 utero should cause the transformation of one of them into a 

 free-martin in a certain definite proportion of cases. But we 

 have seen that the free-martin and its male mate arise from sepa- 

 rate zygotes. From this point of view the free-martin must be 

 interpreted as zygotically female. 2) The somatic resemblances 

 between the free-martin and its mate are not of the order of 

 identical twins. 3) The assumption that the free-martin is 

 male leads to an absolutely incomprehensible sex-ratio, while 

 the interpretation that it is female comes nearer fulfilling the 

 expected sex-ratio. From this point of view also the free-martin 

 is female. 



The only argument that remains for its male nature rests on 

 the anatomy of the internal organs of reproduction, which un- 

 questionably are more or less of the male type. But, as the ex- 

 ternal genitals and the mammary gland are almost invariably 

 of the female type, the argument from anatomy may be made to 

 turn either way depending on what anatomical characters are 

 recognized as diagnostic of sex. In a later section we shall go 

 fully into the anatomical problems involved. Here it may 

 suffice to say that the anatomical argument is necessarily 

 inconclusive. 



In what follows, therefore, we shall treat the free-martin as 

 demonstrated to be zygotically female, and the question becomes 

 how the association of a male and female in utero may so trans- 

 form the female. 



