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BENJAMIN H. WILLIER 



dium of the tunica vasculosa. This primordium shows a degree 

 of differentiation comparable to the condition of the tunica 

 vasculosa of a normal testis of a 4.8-cm. embryo. Blood-vessels 

 from this vascular zone pass to the stroma of the sex-cord 

 region, supplying it with blood. In case H-18 no tunica vascu- 

 losa is apparent, so that the blood-vessels enter the hilus and 

 are distributed in a centrifugal manner to the rete tubules and 

 the sex-cord region (fig. 5). 



Fig. 5 Transverse section through free-martin gonad, H-18. bv, blood-ves- 

 sels; r, rete (note its eccentric position); s, seminiferous tubule; st, tubuli recti 

 connecting rete tubules and seminiferous tubules; ta, tunica albuginea (note 

 absence of tunica vasculosa). X 14. 



These two ways for the distribution of the blood in the free- 

 martin gonads will be understood from the normal arrangement 

 of the blood-vessels in the ovary and in the testis, and in the 

 Hght of the fact that the free-martin gonad is primarily an ovary 

 which is being transformed into a testis. A comparative study 

 of the normal method of distribution in ovaries and testes shows 

 a marked difference. In the testis blood-vessels enter the 

 anterior end, ramify extensively throughout the tunica vas- 

 culosa, from which they send branches inwardly, in a centripetal 

 manner, to the seminiferous tubules and rete tubules (fig. 4). 

 In the ovary the blood-vessels are distributed in a centrifugal 



