xii INTERMEDIATES 129 



or other or both of them in a homozygous or a hetero- 

 zygous state. Moreover, certain of these intermediates 

 will breed true to an intermediate condition of the pig- 

 mentation. A male of the constitution ffPPII when 

 bred with females of the constitution FfPPIi will produce 

 only males like itself and females like the maternal parent. 

 We have dealt with this case in some detail, because the 

 existence of families showing a series of intermediate stages 

 between two characters has sometimes been brought 

 forward in opposition to the view that the characters of 

 organisms depend upon specific factors which are trans- 

 mitted according to the Mendelian rule. But, as this 

 case from poultry shows clearly, neither the existence of 

 such a continuous series of intermediates, nor the fact 

 that some of them may breed true to the intermediate 

 condition, are incompatible with the Mendelian principle 

 of segregation. 



In connection with intermediates a more cogent ob- 

 jection to the Mendelian view is the case of the first cross 

 between two definite varieties thenceforward breeding 

 true. The case that will naturally occur to the reader is 

 that of the mulatto, which results from the cross between 

 the negro and the white. According to general opinion, 

 these mulattos, of intermediate pigmentation, continue to 

 produce mulattos. Unfortunately this interesting case has 

 never been critically investigated, and the statement that 

 the mulatto breeds true rests almost entirely upon in- 



