10 THE GENETIC AND THE OPERATIVE EVIDENCE 



In 1916 I operated on a Sebright male that lived for some months, 

 but died in the summer of 1917. At the time of his death he had 

 assumed a partial cock-feathering, as shown by the feathers in plate 9, 

 figure 3, 3a. Dissection showed that some of the testes had been left, 

 and as is then to be expected, the change was incomplete. 



A MALE SEBRIGHT THAT DID NOT BECOME COCK-FEATHERED 

 AFTER CASTRATION. 



One of the males that had been castrated with the others did not 

 become cock-feathered even after a year. Taking for granted that 

 the castration had been incomplete, the bird was opened, but as no 

 pieces of the testes were to be found in the normal position he was 

 killed and carefully dissected. There were no pieces of testes found 

 in the normal situs. A small whitish patch of material from this region 

 was cut into sections, but no testicular material was found in it. Then 

 a large piece of the back from the region of the attachment of the 

 testes was prepared, but as yet this piece has not been sectioned. Even 

 were a small piece of tissue to be found, it would seem unlikely that it 

 would suffice to hold back all indications of the cock-feathering, for 

 after incomplete removal of the testis there are nearly always at first 

 some indications of the lack of material. The most plausible view here 

 is either that some other gland may have assumed, provisionally, the 

 function of the missing testes, or else a detached piece has not yet 

 been found. Glandular cells like the luteal cells of the ovary have 

 in fact been described by some observers in other organs of the body. 

 As yet I have not found time to make a thorough histological study 

 of the tissues of this bird. 



TRANSITIONAL FEATHERS. 



In several birds new feathers had begun to develop at the time of 

 the operation under the influence of the testicular secretion. After 

 the removal of the testes, these feathers continued to grow and in the 

 absence of the original conditions changed over to the other type. 

 The outer end of these feathers shows the original or normal shape and 

 color, while the inner end shows the new characteristics. Such feathers 

 have been seen in nearly all of my castrated birds; a few from the 

 Sebright will suffice by way of illustration. In plate 10, figure 2a, 

 four such transitional feathers are shown. In a and b two feathers 

 from the hackle are photographed. The first (a) had begun as a normal 

 Sebright hackle feather, as seen in the condition of its tip; the rest of 

 the feather is the same as the feather of the castrated bird. For com- 

 parison with this feather, two (26) from the same bird are shown that 

 began to develop after the testes were removed, i. e., at the same time 

 as the change occurred in the former feather. At the time the latter 



