120 MENDELISM CHAP. 



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 

 transmitted according to the Mendelian rule. But, 

 as this case from poultry shows clearly, neither 

 the existence of such a continuous series of inter- 

 mediates, 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 

 objection to the Mendelian view is the case of the 

 first cross between two definite varieties thence- 

 forward 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 information that is general and often vague. It 

 may be that the inheritance of skin pigmentation 

 in this instance is a genuine exception to the normal 

 rule, but at the same time it must not be forgotten 

 that it may be one in which several interacting 

 factors are concerned, and that the pure white and 

 the pure black are the result of combinations which 

 from their rarity are apt to be overlooked. But 

 until we are in possession of accurate information it 

 is impossible to pronounce definitely upon the nature 

 of the inheritance in this case. 



On the other hand, from the cross between the 



