THYROID FEEDING AND SEX CHARACTERS. 



This misconception led us to suspect that the effect of thyroid 

 feeding on the feathering of the male might be indirect, through 

 an augmentation of the so-called luteal tissue, to whose presence 

 in the testes of Campines and Sebright bantams has been imputed 

 the hen-feathered condition of the males of these breeds. No 

 support for this suspicion was obtained from histological prepa- 

 rations, however, and the observation of the thyroid effect in 

 capons completely disposed of the possibility of it. But that the 

 thyroid effect is not independent of the ovary in certain respects 

 is a fact that will be developed in another connection. 



The intensity of hen feathering in males of hen-feathered breeds 

 differs with the breed. For instance, the male silver Sebright 

 bantam is an absolute replica of the female, in plumage. The 

 male silver Campine, however, though resembling the female 

 closely, differs from it not only in the possession of sickle feathers 

 but in the structure of the hackles, which are laced in the typical 

 male fashion. 



Now the plumage of thyroid-fed Rhode Island Red males, up 

 to the age of 12 weeks, is indistinguishable from that of females. 

 Later on, the males in our experiments developed plumage that is 

 perhaps best described by saying that it was prevailingly male 

 with certain modifications characteristic of the female type. 



In place of typical male hackles (Fig. 6, a, b} with broad 

 marginal lacing of naked barbs, and with sharply pointed tips, 

 thyroid feeding produced hackles with broader and more rounded 

 or truncated tips, and narrower lacing, especially toward the tips, 

 but, more or less irregularly, elsewhere also (c, d). .Saddle 

 feathers (Fig. 7, a, c) were similarly affected, the ends being 

 broader and more rounded, and the laced margin furnished with 

 an irregular inner border owing to the development of barbules at 

 points where the barbs are normally naked (Fig. 7, b) or in 

 exceptional cases, to the absence of barbules in normal situations. 

 We shall have occasion to discuss these irregularities elsewhere. 



The characteristically broad distal lacing of shoulder feathers 

 in normal males (Fig. 8, a) was still more strikingly reduced in 

 thyroid-fed males (b), often, in fact, completely obliterated (c), 

 giving the feathers an undeniably female aspect, as can readily be 

 seen by comparing (c) with (d), the latter being a feather from the 



shoulder of a normal female. 

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