ON STERILE AND HYBRID PHEASANTS. 



By GEOFFREY SMITH, MA., 



Fellow of New College, Oxford; 



AND Mrs HAIG THOMAS, F.Z.S. 



The material for this study consists of four abnormal or " mule " 

 pheasants, which on dissection proved to be females with aborted 

 ovaries, and a series of hybrids between Reeve's pheasant and the 

 Japanese pheasant and Formosan variety of the Chinese pheasant bred 

 by Mi's Haig Thomas and handed over to me for histological examina- 

 tion. Mrs Haig Thomas has also put at my disposal some valuable 

 statistics derived from her extensive experiments in breeding hybrid 

 pheasants of various kinds, which throw an interesting light on the 

 disturbance of the sex-ratio through hybridisation. The examination 

 of the plumage of these birds was made by Mrs Haig Thomas, and 

 I have also had access to her records relating to their behaviour, change 

 of plumage, etc., which occurred while they were living in her aviaries. 

 This paper is, therefore, a joint production, in which Mrs Haig Thomas is 

 responsible for the breeding experiments and myself for the theoretical 

 interpretation. The facts brought out by the study of these various 

 sources throw light on three distinct problems which may be treated 

 separately, first, the cause of the sterility of the hybrids in so far as it 

 is elucidated by a histological examination of the reproductive tissues, 

 second, the assumption of partial male plumage by the sterile females 

 and the correlation of this abnormal plumage with atrophy of the 

 ovary, thirdly, the preponderance of males over females in hybrid 

 pheasants and the question as to how far this preponderance is due 

 to a selective death-rate, and at what period the incidence of this 

 selective death-rate occurs. 



