SEX-INTERGRADES IN FCETAL PIGS. 



(PRELIMINARY REPORT.) 



WINIFRED HUGHES, 



UNIVERSITY OF ALBERTA, EDMONTON, CANADA. 

 (Reported from the Department of Zoology, University of Chicago.) 



The hormone theory as an explanation of the type of sex- 

 intergrade known as the free-martin has hitherto been limited 

 in its application to conditions in cattle. The theory permits 

 however, general applicability, and all species that are able to 

 duplicate the conditions which in bovine species invariably 

 produce the free-martin, would be expected to give rise to similar 

 anomalous forms (Lillie, '17). 



The conditions essential for the production of the free-martin 

 are the establishment of a common circulation between a hetero- 

 sexual pair of individuals at an early stage in their embryonic 

 development. Thus certain sex-hormones liberated into the 

 embryonic blood stream are common to both individuals, and 

 succeed in modifying the normal course of sexual growth. The 

 fact that it is invariably the female structures which are affected, 

 and that they are modified in the male direction, leads to the 

 further assumption that the male hormones are more precocious 

 in their development than those of the female, and consequently 

 are able to exert their influence without any counteraction on 

 the part of the female. This assumption receives considerable 

 support from histological evidence in that it has been observed 

 that the interstitial cells, the supposed seat of sex-hormones, 

 develop earlier in the testis than in the ovary. In cattle, such 

 cells first occur in testes of 3 cm. embryos, and in ovaries of 

 82 cm. females (Bascom, '23). A similar precocity of male 

 interstitial cells has been stated to occur in the pig (Allen, '03). 



Species which are typically uniparous and in which the placenta 

 is of the diffuse type, offer the most favorable opportunities for 

 the production of chorionic fusions and resulting complications. 



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