92 EVOLUTION IN COLOR-PATTERN OP THE LADY-BEETLES. 



The hypothesis which seems to me to satisfy best the facts of heredity 

 here and to be consistent with those of variation and distribution in these 

 beetles is that of characteristic prepotency. Since the word ' ' prepotency ' ' 

 is used in speaking of an individual, I would propose the term "preponder- 

 ance " for the prepotency of characteristics. It is necessary to distinguish 

 this from dominance. In dominance without the aid of selection there is 

 no gain in numbers, since there is no germinal advantage with the domi- 

 nant characteristic. In preponderance there is a germinal advantage, so 

 that the characteristic gains in numbers without the aid of natural selec- 

 tion or even conceivably in opposition to it. In a character with blending 

 inheritance, preponderance shows itself by the progeny resembling in the 

 long run one of the two opposed characteristics more than the other. 



In segregate characteristics it may show itself in the guise of hyper- 

 dominance, that is, by the numbers of the dominant characteristic being 

 excessive, or in a differential tainting of the extracted homozygotes. Cases 

 that seem to be more easily explained by resorting to preponderance (or 

 subponderance) are the deficient proportions of most of the elementary 

 species of Oenothera where crossed with 0. lamarckiana (de Vries, 1901) , 

 the deficient proportions of abnormally veined Ampelophila when crossed 

 with the normal (Lutz, 1907), the deficiency of polydactylism when crossed 

 with the normal in man (Davenport, 1904), the excessive proportion of 

 booting in booted X bootless in poultry (Davenport, 1906), deficient pro- 

 portion of the all-black Lina scripta X normal (McCracken, 1907), exces- 

 sive proportion of spotted Lina scripta in L. scripta X black L. scripta, and 

 excessive proportion of black Gastroidea dissimilis in black X green 

 (McCracken, 1906). 



Many breeds of animals have what are called "faults," which are the 

 distress of their breeders. These faults are sometimes merely the normal 

 traits of the wild species or ancestral variety from which the variety is 

 obtained, and their persistence would not be a serious problem except that 

 the breeder is trying to handle so many characteristics. There is a greater 

 degree of persistence in some, however, that can not be thus explained. 

 Of recent years, these have been explained as the products of the meeting 

 of heterozygotes which reveal recessive characters which may not have 

 been seen for several generations, because the heterozygotous individuals 

 had not mated before. This is sometimes true without doubt, but in con- 

 sidering these cases from Leighton (1907, p. 321), and Simpson (1903, p. 

 117) , the hypothesis of preponderance may well be considered. Here the 

 preponderance shows by the difficulty with which the characteristic is 

 submerged. 



"Litters [of the white English terrier] frequently show the blemish of 

 a spot of brindle or russet. These spots usually appear behind the ears or 

 on the neck and are of course a disfigurement on a dog whose coat to be 

 perfect should be white." This breed was quite popular at least 40 years 

 ago, and any color or marking disqualifies. 



