26 



THE AMEBIC AN NATURALIST 



[VOL.LII 



Other Charactebs m the Cross 

 Three other characters are conspicuously present in 

 the fantails besides the tail, viz., the white plumage, the 

 carriage of the bird, and the shaking of the head and 

 neck. The dominance— incomplete— of the white of the 

 fantail was noted, 8 but the mixtures that appeared both 

 in Fj and F 2 make it probable that the results are not 

 due to a single factor. The extraordinary position of the 

 fantail pigeon with its head thrown back until it touches 

 the tail feathers appears also to be due to at least as 

 many factors as is the number of feathers in the tail; 

 for it was not recovered in any of the F 2 birds, although 

 in the back cross there were birds that showed some ap- 

 proach to the fantail posture. The shaking of the head 

 disappeared in F x and indications of it were seen occa- 

 sionally in F 2 and especially in back crosses. The char- 

 acter is of such a kind that its study is difficult, and it may 

 well be an expression of some structural modification of 

 the body rather than any direct psychological factor. 



Castration of Male 

 The absence of marked secondary sexual characters in 

 the male, characters that are so conspicuous in many 

 other birds, suggested the possibility that here, as in the 

 Sebright male fowl, the suppression of the male plum- 

 age might be due to substances developing in the testes. 

 Unlikely as this seemed (because pigeons with diseased 

 testes would probably have occurred and any change re- 

 corded), nevertheless I tried the effect of castration on 

 one young F 2 male that was just weaned. Some feathers 

 were removed at the same time. The bird was kept 

 for about five months and did not show any change in 

 its plumage. It appears probable, then, that there are 

 no genetic factors in pigeons, like those in the Sebright, 

 which, acting through the testes, suppress the develop- 

 ment of the plumage in the male. 



