750 



THE AMERICAN NATURALIST 



[Vol.XLIX 



character concerned is, in its grosser aspect, clearly mid- 

 way between the corresponding traits of its two parents, 

 although a closer inspection reveals a mosaic the elements 

 of which are the parental traits quite unchanged. The 

 difference between the Andalusian fowl and the short- 

 horn cattle cases seems to be as follows: In the Anda- 

 lusian each gene influences the entire plumage-color, and 

 appears to be struggling unsuccessfully, as it were, for 

 the supremacy in somatic expression, thus resulting in a 

 very fine and quite generally distributed blend or mosaic ; 

 while in short-horn cattle the controlling genes are double 

 the number, each pair being confined to specific coat 

 areas in somatic expression, and the resulting mosaic, 

 although quite variable in coarseness, is always relatively 

 coarse and is also quite definitely patterned. 



Thus, normally (for the exception see the note in Fig. 

 6) in Area 1 the gene "W" is clearly dominant over the 

 gene ' ' E. ' 1 In Area 2 the gene " R " is dominant over its 

 absence. There seems to be in Area 2 no competing or 

 allelomorphic gene whatever — it is simply "B" or its 

 absence, i. e., albinic white; whereas in Area 1 the "W," 

 which is epistatic to "R," will leave "R" by its absence. 

 The evidence for all this consists in the fact that a white 

 short-horn (which is evidently dominant white, always 

 duplex, in Area 1, and always recessive white in Area 2) 

 will, when crossed with a black Angus, which is dominant 

 black for its entire coat, give in the offspring a calf domi- 

 nant white, simplex, in Area 1, and black, simplex, in Area 

 2— the familiar 1 'blue roan" in cattle. That in short-horn 

 cattle the genes " W" and 1 'R" lie in the same chromo- 

 some is sufficiently proved by the fact that the color 

 pattern is never reversed, that is to say, in bi-colored indi- 

 viduals of whatever coarseness of mosaic, Area 1 is 



(Note:— men this paper on coat-color was written it was pointed out that 



modified interpretation, involving linkage and a variation in genie valence, 

 as explained in the text and Fig. 6 of the present article, accounts for prac- 

 tically all of the observed facts.) 



