give the groups shown in Fig. 7. A comparison of these 

 groups shows that there is a relatively large number of 

 high-feathered tails amongst the whites, while among the 



blues, the 12-feathered tails are relatively more frequent. 

 A not improbable interpretation of this relation is that 

 the principal factor for white is linked to one or more of 

 the factors for increased number of feathers. 



