256 



T. H. MORGAN. 



the right side there was an almost complete organ. The comb 

 was large, measuring half an inch in height and two inches in 

 length. Each wattle was one inch across. The condition of the 

 testes accounts for the failure of the bird to change over. 



These few experiments suffice at least to show that it is pos- 

 sible to cause the total degeneration of the testis if ligation is suc- 

 cessful ; and further that unless the testes are entirely removed 

 the complete change-over to cock-feathering does not take place. 



lit 



FIG. ii. Original feathers, a-d, July 10, and later feathers November 15, 



i, and March 15, 



They also show, however, that some change in the direction of 

 cock-feathering will take place if some of the testis is removed, 

 and the amount of the change is roughly proportional to the 

 amount of testis present. The comb is a sure index of the 

 amount of the testes left. It appears that a smaller amount 

 of the testis suffices to keep the comb at or near its normal size 

 than to keep the feathers true to type for hen-feathering. For 

 a complete change to cock- feathering it is essential that all of the 

 testis be removed. These results accord fully with the results 

 that I have obtained by castration. The chief significance of the 

 results is to show that adult birds can be successfullv used if 







ligating is employed instead of castration. 



