SEX-INTERGRADES IN FOETAL PIGS. 127 



region corresponding to that in Fig. 9, indicates the difference in 

 size of the two Wolffian ducts. The left duct is approximately as 

 small as its accompanying Miillerian duct, and even that on the 

 right does not approach the normal size. The Miillerian ducts 

 could be traced throughout their whole length, and the left was 

 especially large. Degeneration does not occur in the region 

 indicated in diagram until a later date, hence no irregularities in 



size are evident here. 



DISCUSSION. 



A considerable number of sex-intergrades in adult swine have 

 been described during the last few years. The free-martin 

 condition as a possible explanation has been discussed and 

 abandoned partly on the grounds that chorionic fusions with 

 their complications have not been described in the pig. There 

 is no doubt that the first three cases described in this paper would 

 have developed into typical sterile free-martins such as occur in 

 cattle. Their gonads might be structural testes, or, in con- 

 sideration of the fact that a certain amount of secondary sex- 

 cord proliferation takes place, they might possibly be ovo-testes. 

 The temporary appearance of the Pfliiger cords and their conse- 

 quent degeneration, as described in the first two cases, is coinci- 

 dent with the development of the interstitial cells in the female 

 gonad. It has been pointed out by Allen ('03), that these cells 

 first appear in scanty quantities in the ovary, at the same time 

 as they appear in the testis in large numbers, but that they 

 subsequently disappear in the ovary not to reappear until a 

 much later period of development. With their disappearance 

 the male hormone is able to exert its influence without any 

 counteraction on the part of the female, and degeneration of 

 the few female sex-cords results. 



Case No. 4 presents a different proposition. Similar ab- 

 normalities in adult swine have been explained by Crew ('23) 

 on the hypothesis of quantitative sex-differentiating stimulus. 

 A minimum amount of stimulus is required at certain critical 

 moments during development for complete organization of one 

 sex and suppression of the other. A retardation in the production 

 of such stimulus, or an insufficiency in quantity thereof, results in 

 incomplete organization of the one sex and suppression of the 

 other. In the case under discussion, insufficiency of the required 





