124 WINIFRED HUGHES. 



lucida drawings through the widest parts of gonads of the female 

 twin, a normal female, and the male twin. The reduced size 

 of the free--martin ovary is at once apparent, such inhibition of 

 growth being, as in bovine forms, the initial stage of modifications 

 brought about by the action of the male hormone. In addition 

 to reduction in size, there is also inhibition of characteristic 

 ovarian differentiation. In the male, the germinal epithelium is 

 reduced to a single layer of cells, and is separated from the 

 primary sex cords by a well-differentiated layer of fibrous 

 connective tissue. The rete occupies a central position, and 

 radiating from it are the primary sex cords. In the normal 

 female, the germinal epithelium has undergone extensive pro- 

 liferation, and now forms a thick cortical zone of secondary 

 cords. The primary albuginea lying between the medullary and 

 the secondary cords is embryonic in type, and lacks the character 

 of the male structure. The medullary portion of the ovary is 

 occupied by the rete, and a few remaining medullary cords. 

 In the free-martin gonad the cortical zone of secondary cords is 

 practically absent. These cords commence their proliferation 

 from the germinal epithelium in 25 mm. embryos (Allen, '03). 

 Consequently their absence in a 65 mm. individual indicates 

 decided inhibition of female differentiation. The rete is con- 

 spicuously large, but most of the medullary cords have under- 

 gone degeneration, and are present as an unorganized mass of 

 cells. The cortical region consists largely of connective tissue, 

 not so well differentiated as in the male, but forming, nevertheless, 

 a definite layer beneath the epithelium. The germinal epithelium 

 has for the most part been reduced to a single layer of cells, but 

 in a few places there is what I take to be the initial stages of 

 sex cord formation. A few clumps of cells appear to have been 

 cut off from the epithelium, and are wandering in the albuginea 

 where they are apparently undergoing degeneration and ab- 

 sorption. 



Differentiation of the genital ducts has barely commenced in 

 embryos of this age, therefore irregularities have not occurred to 

 any great extent. The narrowing of the Wolffian duct which 

 takes place in normal females of this age, had not occurred in 

 the free-martin. 



