128 MENDELISM chap. 



the two true breeding forms in the ratio 2 : i : i. We 

 took the view that the blue is the heterozygous form ; 

 that the presence or absence of a single Mendellan 

 factor only is concerned in this instance. Nor in 

 the light of such facts as we possess is there any- 

 thing to contradict this view. Nevertheless, in the 

 light of what has been learned from the sweet-pea, 

 we may do well to remember that the case of the 

 Andalusians may not really be so simple as it 

 appears at first sight. It is not inconceivable that 

 two factors are concerned, and that the blue is 

 heterozygous for both of them. Were this so, and 

 were the two factors to exhibit repulsion of a high 

 intensity, perhaps even higher than that found 

 for the factors B and E in the sweet -pea, it 

 would accord with the general results obtained in 

 Andalusian breeding. The criterion between this 

 view of the case and the one taken earlier would be 

 the rare appearance of a fourth form, comparable to 

 the red hood in the sweet-pea. So far we have no 

 evidence that such a form exists, and until it is 

 found we may leave the blue Andalusian fowl 

 undisturbed in its claim to simple heterozygosity. 



We may now go on to consider a further 

 complication connected with this phenomenon of 

 coupling and repulsion. This relation exists between 

 the factors for blue {E) and for long pollen (JS) in 

 the sweet-pea. But, as we have seen, it exists also 

 between the factors for blue {R) and for the erect 

 standard (£"). Since L and E both bear a similar 

 relation to (5) the question naturally occurs — What 

 relation do they bear to one another ? Experi- 

 mental data for answering this question have been 



