EFFECTS OF GONAD GRAFTS IN CHICKS 



11 



c. Comparison of growth of testis grafts and ovary grafts. It 

 was generally found that testis tissue grew faster and more 

 readily than ovary tissue. Although the ovary grafts as a whole 

 exhibited considerable growth, the amount of new growth, that 

 is of folhcular ovarian tissue, was rather small as a rule. In 

 the case of testis grafts, on the contrary, a well-marked new 

 growth of testis tissue was often found, in spite of the smaller 

 size of the grafts as a whole. In other words, ovary tissue shows 

 a greater tendency toward necrosis and less tendency toward 

 growth and differentiation than testis tissue. We cannot at 



TABLE 3 

 Showing age of the embryos at the time of grafting and number of embryos of each 

 age which were affected by the presence of the graft 



present give any explanation for this difference. It may be 

 suggested, however, that under the same physiological conditions 

 ovary tissue requires a more rapid or more abundant nutritive 

 supply than testis tissue, or that ovary tissue is less resistant to 

 a foreign environment than testis tissue, or that both factors are 

 are responsible. 



d. Age of the embryo most suitable for grafting. The organs 

 which were grafted were taken from birds of various ages, from 

 nine-day-old embryos up to adult fowls. The ages of the 

 embryos upon which the grafts were implanted are given in 

 table 3. 



