210 THE AMERICAN NATURALIST [Vol. XLIII 



or (because of the masking qualities of black pigment) 

 with red hair. 



What is the relation of this principle to the law of 

 alternative inheritance? The latter is only a special 

 case of it. When characters A and B are crossed the 

 more intense character appears in the offspring— the less 

 intense character is recessive— the "heterozygous" chil- 

 dren do not exceed the more intense parent. If, now, two 

 such heterozygous persons be mated, one fourth of their 

 offspring show the recessive condition, which by hypoth- 

 esis is of a lower grade than that possessed by the par- 

 ents ; the remainder of the offspring may attain the grade 

 of their parents; but they will not exceed that grade. 

 This principle of the non-transgressibility of the upper 

 alternative inheritance only, but also for blending in- 

 heritance—indeed, it seems to be of universal appli- 

 cability. 



An exception to this rule is exhibited by some heter- 

 ozygous forms. The cross of a high-combed fowl and 

 a low-combed is a fowl with one intermediate grade 

 of comb. Two heterozygous combs in the parentage 

 throw, inter alia, high combs. Not all cases of heter- 

 ozygous forms constitute exceptions to this law of the 

 non-transgressibility of the upper limit, and human hair 

 color seems, even in the heterozygous condition, to follow 

 the law. The workings of the principle are veiled in 

 some cases of cryptomeric characters, i. e., built up of 

 hidden factors. 



Certain important consequences flow from this prin- 

 ciple. These one of us has pointed out in a brief com- 

 munication to Science? If the progeny stands on the 

 average in respect to a character at a lower grade than 

 the parents then, if inbreeding is practised, the two 

 parents of the next generation will probably have this 

 character at a lower level than their parents and will pro- 

 duce children having the character less well developed 

 than they have it themselves. If inbreeding be practised 

 for several generations it is clear that in some, at least. 



8 Vol. XXVIII. pp. 454-455, October 2, 1908. 



