ON A CASE OF UNILATERAL DEVELOPMENT 

 OF SECONDARY MALE CHARACTERS IN A 

 PHEASANT, WITH REMARKS ON THE IN- 

 FLUENCE OF HORMONES IN THE PRODUC- 

 TION OF SECONDARY SEX CHARACTERS. 



By C. J. BOND, F.R.C.S., Leicester. 



Description. 



The skin now described is that of the white ringed Formosan 

 variety {Phasianus Tm^quatm) of the Chinese pheasant. 



On the left side (cf. PL X, figs. 1 — 4), it shows the plumage and 

 spur of the male bird. The red portion of skin round the eye is much 

 larger on the left than on the right side. The head and neck feathers 

 are blue green, iridescent on both sides but more so on the left. There 

 is a semilunar patch of the white collar feathers strictly limited to the 

 left side of the neck. The wing primaries and coverts are of the female 

 type though a few male plumage feathers appear in the left wing 

 coverts. The tail coverts show marked male characters, more especially 

 on the left side. The breast feathers, which are rufous in colour, 

 especially on the left side exhibit the black tipping seen in the male 

 bird. The left leg shows a well developed spur, pointed, and of the size 

 found in the cock of the second year (cf PL XI, fig. 5). On the right 

 leg there is no spur but only the usual rudiment or scaur found in the 

 hen pheasant (PI. XI, fig. 6). 



The bones of the left tarsus and phalanges are longer and thicker 

 than the corresponding bones in the right leg. 



The tail feathers (rectrices) are especially interesting. While the 

 assumption of male plumage is more or less confined to the left side 

 in the head and neck and trunk and limbs, it is not so limited in the 



Journ. of Gen. iii 14 



