BLENDED INHERITANCE 179 



pure-bred parents of one kind only would have to enter into 

 the cross, and then in time it is conceivable that the other 

 character might be apparently eliminated, just as the colour 

 of a portion of the mixture of equal parts of water and claret 

 would be lost by taking half of the mixture and adding to it 

 an equal quantity of water, then taking this mixture and 

 doing the same thing, and so on for an indefinite number of 

 times. 



Before Mendel's interesting discovery became generally 

 known the different modes of inheritance were described as 

 blended, exclusive, and participate. 1 



In blended inheritance of a particular character, the off- 

 spring exhibits an intimate mingling of the characters of 

 both parents. The character, in fact, is intermediate between 

 the corresponding characters appearing in the two parents. 

 Thus the child of a white man and a black woman is 

 generally brown. If a narrow-leafed willow be crossed 

 with a broad-leafed willow, the shape of the leaf in the 

 offspring is intermediate between the two. In several plants 

 the hybrids show an accurate mean in many characters 

 between those of the two parents. 2 It may be, however, 

 that though the character of both parents are recognisable, 

 the one preponderates over the other. Thus mules are 

 sometimes more like donkeys than like ponies, but at other 

 times this resemblance may be reversed. The characters 

 which preponderate are called " prepotent." 



1 Galton, Natural Inheritance, p. 7. 



2 Macfarlane, J. M., "A Comparison of the Minute Structure of Plant 

 Hybrids with that of their Parents," &c., Trans. Roy. Soc. Edinburgh, xxxvii., 

 1891. 



In 1902 I investigated a cross between the bream-flat (Abramis blicca) and 

 the rudd (Leuciscus erythrothalmus). The characters of the cross appeared to be 

 a definite mixture between the two parent forms. The shape, body measure- 

 ments, and head measurements were intermediate between the two parent forms, 

 as were apparently all the other characters. For instance, in the anal fin of the 

 bream-flat there are from 22 to 27 rays ; in the rudd there are from 13 to 15. In 

 the cross the number of anal fin rays was 17, and the number was apparently 

 much more constant in the cross than in either of the parent forms, for in the 

 numerous specimens examined the same number of anal fin rays was always 

 found. Other cases of blending are given on pp. 117-9. 



