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THE AMERICAN NATURALIST [Vol. XL VI 



has nothing to do with dominance . . . dominance is an 

 invariable attribute of particular characteristics. ' ,15 Plate 

 (1910), on the contrary, observes, "But a variety of facts 

 seem to indicate that a reversal of dominance may occur 

 under certain circumstances and a dominant character 

 may become recessive, and vice versa." 1 * Such reversal 

 of dominance would appear to be the case in a compari- 

 son of the mule (cross between ass J 1 and horse ?) and 

 the hinny (cross between the horse <$ and the ass ?). 



When antithetic characters or functions meet in hered- 

 ity, there is either "prepotency," or 1 1 dominance, ' ' or 

 "recession" (i. e., latency), or "inhibition," a something 

 which indirectly prevents the appearance of characters, 

 or "imperfect dominance," or "blending." In brief, 

 there are degrees of separableness and antithesis. 



Dominance, Conservative or Progressive. — It will be 

 seen at once that progressive evolution through discon- 

 tinuity would depend on the dominance of racially neiv 

 characters and types. The experimental evidence is con- 

 flicting, it does not show that new characters are neces- 

 sarily dominant. 



There are many instances of dominance of wild species 

 (older type) over domesticated species (newer type); 

 thus De Vries suggested (1902) that the dominant char- 

 acters are those which are racially older. One case among 

 the mammals is that the wild gray color in mice domi- 

 nates over grades below it, black, brown, and white 

 (Plate, 1910). 



Examples of dominance in single characters are that 

 more intense dominate over less intense colors (Plate, 

 1910, Davenport, 1907) ; in the eyes, brown over gray, 

 gray over blue; in the skin, brunettes over blondes (Dav- 

 enport, 1909), piebalds over pure albinos (Plate, 1910). 

 In the hair, wavy or spiral forms dominate over straight 

 (Davenport, 1908). This would have some bearing on the 

 discontinuous fading out of color in desert races like the 

 quagga, which lost all the stripes of its relative the zebra. 



"Darbishire, op. tit., p. 96. 

 14 Plate. 



