EFFECTS OF GONAD GRAFTS IN CHICKS 21 



mlillerian duct is greatly enlarged and differentiated in the 

 direction of the adult oviduct; the terminal portion of the right 

 miillerian duct is generally still present (fig. 9, 10). Affected 

 embryos whose gonads and ducts are similar to this condition 

 are regarded as female-type embryos. It is to be understood 

 that the gonads and ducts of the affected embryos exhibited all 

 possible gradations between apparently normal embryos and 

 intersexual conditions, in which cases, the embryos could not be 

 definitely assigned to either sex. 



In table 6 the experimentally obtained embryos are classified 

 into three categories: markedly affected embryos, slightly 

 affected embryos, and those apparently non-affected. Since, 

 however, all gradations exist between these three classes, it is 

 to be understood that the assignment of some of the embryos 

 into such categories is largely arbitrary. 



In general it may be said that whenever the grafts exhibited 

 a good growth, the embryos were affected, but when the grafts 

 grew slightly or not at all the resulting embryos were nearl}^ 

 normal or apparently non-affected. 



I shall now describe in detail the anatomical characters of a 

 number of affected embryos, selecting those which showed 

 distinct alteration of their urinogenital systems toward an inter- 

 sexual condition. In these descriptions each embryo is desig- 

 nated by a double number, the first one referring to the number 

 of the experiment, the second to the number of the particular 

 embryo in that experiment. For instance, embryo 27-6 desig- 

 nates the sixth egg operated on in the twenty-seventh experiment. 



b. Description of embryos affected by testis grafts. 



1. Embryo no. 27-6 (fig. 11, 12). Operated May 7, 1918. 

 One-fifth of the left testis of a one-month old chick was grafted 

 on the membranes of an embryo nine days old. Testis 5 mm. 

 long; grafted piece about 1 mm. square. Examined May 17th; 

 embryo developing and graft with vascular connections, of small 

 size, however. Age of embryo, 19 days; duration of graft, 10 

 days. 



Result: Right gonad of affected embryo 4.1 x 1 mm.; left 

 gonad 4.1 x 0.8 mm.; peculiar black pigmentation over half of 



