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THE AMERICAN NATURALIST [Vol. XLVII 



same race, since all alike will lie characterized by irregularity in dis- 

 tribution of the same two factors A tricolor race on this hypothesis 



It will be observed that this hypothesis rests on the 

 fact that two characters are irregularly distributed, viz., 

 black and white, and on the assumption that yellow is al- 

 ways uniformly distributed. What is meant by irregu- 

 larity in the distribution of a character except as a state- 

 ment of a fact is not clear. The words suggest somatic 

 distribution of factors, at least the factors for black and 

 for white, that have come from the germ-cell. On the 

 other hand, it may be that the heritage of every cell is like 

 that of all the others ; and regional differences give rise to 

 difference in pigment development. But on the last view 

 the irregularity in distribution of the character is not 

 explained by referring it to regional differentiation, for 

 the question is left as uncertain as before. 



There may be involved, moreover, the question of the 

 inheritance of a pattern or patterns, for, if the spots are 

 localized, as Castle says in his earlier papers, or, at 

 least, if spot-areas are present, the distribution of black 

 and white may not be so simple a problem as indicated 

 by the hypothesis under consideration. Furthermore, if 

 spotting is due not to one or two, but to several factors, 

 a further complication is present. And finally, if a given 

 spot is black on one side of the body and its mate is yel- 

 low on the other side, even the assumption of many fac- 

 tors will have difficulty in explaining the results unless a 

 somatic segregation of the factors is assumed. Until 

 these questions have been cleared up the explanation of 

 the inheritance of spotting is likely to remain obscure. 



Hagedoorn has recently 2 pointed out that for the oc- 

 currence of spots in rabbits and in certain other animals 

 (cats, goats), Castle's explanation may not apply. He 

 concludes that the distribution of color in these tricolor 

 animals must depend upon the cooperation of many fac- 



2 Ameb. Nat., November, ]912. 



