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THE AMERICAN NATURALIST [Vol. XLIV 



blonds. Some of the latter are doubtless without blonds 

 by chance, owing to the small number in the family, just 

 as there are 30 families in the entire 88 without brunet 

 offspring or 39 without intermediates. That all of the 

 families without blonds are not so by chance is probable 

 from the following considerations: (a) blonds are al- 

 most (11:12.8) as numerous as the other two classes 

 together yet the latter are both absent in the offspring 

 of only eleven families; {b) there are more large fam- 

 ilies that are blondless than that are without brunets 

 and intermediates, and when a large family is without 

 offspring of a particular class the result is less probably 

 due to chance. Finally, owing to the fact that the de- 

 velopment of potential pigment is frequently retarded, 

 some of the families with " blond" offspring would later 

 be without blonds. We may conclude, then, that some 

 of the blondless fraternities are so because all of their 

 members have the determiner for skin pigmentation and, 

 consequently, in the brunet X blond matings some of the 

 brunet parents are duplex in skin pigment. But the off- 

 spring of these duplex parents are not all alike ; half of 

 them are " intermediate" and the remainder "brunet." 

 This result suggests that brunets may carry the "inter- 

 mediate" grade of skin pigmentation as a hidden — 

 hypostatic — factor. 



In the families containing blond offspring, expectation, 

 on the hypothesis of segregation, is that half of the off- 

 spring shall be blond and half pigmented in full or 

 intermediate grade. Actually blonds are to non-blonds 

 as 193:149 or as 1.3:1. The excess of blonds suggests 

 that some of them are immature and potentially pig- 

 mented, the families really belonging to the right hand 

 side of the table. 



(c) Brunet X Brunet (Table III).— When both pa- 

 rents are brunets there may, on the segregation theory, 

 be two classes of families, namely, a class in which both 

 parents produce germ-cells without the pigment deter- 

 miner and a class in which at least one parent produces 

 no such germ-cells. In the former case only are blond 



