MULTIPLE FACTORS 



233 



A race of pigeons called fantails differs from other 

 pigeons, and from birds in general, by the large num- 

 ber of feathers in the tail. The ordinary pigeons have 



p, 



1 



I I I L 



I 



p > ■ 

 -f'-J L 



zA. 



l_L 



iliii 



I I 



Back cross 



!_{_ 



J L 



Fig. n?. — Illustrating the results of a cross between pigeons with 12 

 tail feathers and a race of fantail pigeons with from 28 to ;iS tail feathers. 

 The number of feathers in Pi, Fi, Fo, and the off.spring of the backcross 

 (Fi by fan tail) is given. In each rase the numbers on the base line stand 

 for tail feathers. The vertical rows are the classes. 



twelve tail feathers; the fantails used in the cross 

 have from 28 to 38 tail feathers. The Fi hyln-ids 

 (41 birds) have from 12 to 20 tail feathers; the F2 

 have 12 to 25 in a count of 67 birds. When the Fi 



