252 



T. H. MORGAN. 



two days the birds almost died. They lay on the floor of the 

 cage with their muscles convulsively contracted. They were im- 

 mediately fed on milk by means of a pipette and later on bread 

 and milk. In the course of a week they had completely recov- 

 ered. At the time of the operation, a few weeks later, they were 

 active and very healthy-looking birds. 



The testes of the Sebright were tied off on Sept. 29, 1919. A 

 few feathers from typical regions were pulled out and are shown 



FIG. 7. Original feathers, ad of Fig. 6 ; and later feathers, a 1 d l , November 



15, and a l d 2 , March 15, 1920. 



in Fig. 2, a, b } c, e. By Oct. 24 the new feathers had begun to 

 come in. They were typical cock-feathers. When the last photo- 

 graph was taken, Fig. I, April 8, 1920, the bird had changed over 

 almost completely to cock-feathering. The comb was small; not 

 more than a third its original size. The extent to which the 

 change had taken place is best shown in the feather-chart, Fig. 

 2, a 1 -? 1 , where one of each of the original kinds of feathers is 

 placed side by side with the new feather from the same region. 



The second bird operated upon, called " Lamey," Fig. 3, was a 

 yellow, back-cross, hen-feathered cockerel, one year old. Its 

 testes were ligated in May, 1919. It went over towards cock- 

 feathering during the summer (July, 7), as shown by the feather- 

 chart, Fig. 4, a 1 , b 1 , c 1 , rf 1 . Both the old and the new feather's 

 were present at this time and one of each from typical regions 



