iv] A Dominant Piebald Type 87 



Hurst's experiments (160) showed that this pattern is 

 an ordinary dominant to self-colour a definite but most 

 unexpected result. 



More lately Miss Durham (116) has found a dominant, 

 and doubtless analogous, pied type in mice. So far no 

 criterion has been discovered which distinguishes this 

 dominant pied pattern externally from the recessive ones, 

 but in breeding the distinction is perfectly sharp. It is 

 likely that the factor for this new dominant was brought 

 into Miss Durham's strains by the introduction of the type 

 called "black-eyed white," but the evidence is not perfectly 

 clear on this point. As may be supposed, the combination 

 of the dominant pied with the recessive pied in the same 

 strain gave results which it was impossible to disentangle, 

 though when each of these types was isolated the course of 

 descent was perfectly clear. The case is interesting not 

 merely as exemplifying a new kind of factor, but as illus- 

 trating a type of complication that may very possibly have 

 to be reckoned with in other difficult and as yet incom- 

 prehensible sets of phenomena. 



Another example of a pied condition dominant to self- 

 colour has been seen in our poultry experiments (22); but 

 since in fowls some of the wholly white breeds are prac- 

 tically dominant in whiteness, it is only to be expected that 

 some of the partial whites should also show dominance. 



In plants, as in animals, no general rule can be laid 

 down as to the dominance of self-coloured or parti-coloured 

 flowers. In the Sweet Pea, for example, the old-fashioned 

 " Painted Lady" (see Plate V) has a red standard and 

 wings nearly white. It is thus a bi-colour type, but it is 

 dominant to the self-coloured reds and pinks. On the 

 other hand in Antirrhinum the self-coloured types are 

 always dominant to the " Delilah " forms which have the 

 lips coloured and the tube or throat white, as was first 

 shown by de Vries. Miss Wheldale who has since worked 

 on a large scale with Antirrhinum (303) found that for 

 each shade of flower which exists as a self-colour, a corre- 

 sponding Delilah or white-tubed type can be made which 

 behaves to the corresponding self-colour as a simple reces- 

 sive. 



