THE 



AMERICAN NATURALIST 



Vol. LII. January, 1918 No. 613 



INHERITANCE OF NUMBER OF FEATHERS OF 

 THE FAN TAIL PIGEON 



PROFESSOR T. H. MORGAN 

 Columbia University 



Sevebal years ago I began to study the inheritance of 

 the number of the tail feathers in fantail pigeons, partly 

 because of a challenge that I would not recover the fantail 

 in the F 2 generation, the implication being that the in- 

 heritance was not Mendelian. The race of fantails is a 

 very old one and the pigeons have been very intensively 

 selected by fanciers for many years. It was therefore to 

 be expected that several modifications had in time been 

 accumulated in the direction of selection. Nevertheless, 

 it was to be expected that if a sufficient number of indi- 

 viduals were bred, the original type would reappear. If 

 two factors in homozygous condition are essential for the 

 reappearance in F 2 of the original fantail, then such an 

 individual is expected once in sixteen cases ; if three fac- 

 tors, once in sixty-four cases ; if four, once in two hundred 

 and fifty-six; if five, only once in 1,048 cases, etc. This 

 relation holds if the fantail factors are all recessive, but 

 fewer factors are called for if one or more of them is 

 dominant, and the question will be still more complicated 

 if the highest reaches of the variation are due to modify- 

 ing factors acting only in the presence of other factors. 



It seemed unlikely, however, that the situation would 

 be found to be as simple as this; for, in the first place, 

 there is no fixed number of tail feathers characteristic of 



