SEXUAL CHARACTERS OF SOME DOMESTIC BIRDS. 39 



as long as those in which the removal of the ovary was complete, they 

 were otherwise similar. The spurs became attached to the shank 

 bone and had the same symmetry as those from completely castrated 

 hens. Apparently, the dependence of the spurs upon the internal 

 secretion is relatively slight, or, to look at the matter the other way, 

 the inhibition exerted in the female upon the development of the spurs 

 is so slight that once development starts the hormone is not always 

 able to check it. 



EFFECTS ON THE VOICE AND ASSOCIATED ORGANS. 



Castrated ducks of both sexes, with the exceptions noted above, have 

 undergone no change in voice. Each has retained the voice of the 

 normal bird and each exercises its voice in a manner and to a degree quite 

 the same as the uncastrated bird, except that some castrated females 

 occasionally give voice to a sound similar to the drake's. Nor has any 

 change been observed in the development of the syrinx in either sex. 



In fowls the effects are more marked. Castrated individuals of each 

 sex are disinclined to give voice to any sort of sound. Capons are 

 capable of giving voice to all the sounds of which the cock is capable, 

 but rarely do so, remaining (so far as ordinary experience goes) voice- 

 less for long periods of time. Of course, it may happen that they use 

 their voice more than noticed, but certainly to no such degree as that of 

 the cocks nearby. 



The castrated females have been equally quiet. I have never heard 

 one crow or attempt to crow. One has occasionally been heard to cluck, 

 making a sound that resembled the calling of the cock to the hens for a 

 tid-bit. Another was induced to " cr-r-r-r-k " like a hen on one occasion. 

 Aside from these instances, and a squawk when handled roughly, they 

 remain voiceless. 



EFFECT ON THE MOLT. 



As far as my observations go, castration with one exception has not 

 influenced the molt of the capon. A definite statement in regard to the 

 molt of the poullard can not be made at present. In some instances a 

 molt comparable to the summer molt of the ducks has occurred, with 

 corresponding changes in plumage, as described for No. 4471. A com- 

 parable change, noted for No. 3840 and No. 2058 in 1915, has been 

 described in detail elsewhere (Goodale, 1916). Other individuals, how- 

 ever, may not pass through such a molt, while the same individual may 

 not show the molt each year. Thus No. 4471 exhibited the molt in 1914, 

 but not in 1913 or 1915. No. 4290, though of the same age as No. 4471, 

 did not pass through this molt in either of her two adult summers. 



The castrated ducks, however, have behaved very differently. They 

 molt several times each year and often without any definite relation to 

 the normal molts of the adult. During the early period of their life, 

 while they are growing the juvenile and adult coats of feathers, they 

 molt at the same time that the normal birds do. The normal adult 



