ALLEN. — TlIK II KUEDITY OF COAT COLOR I\ MICK. 105 



present, a total of G88 young. By the Meiideliau principle of segre- 

 gation, yV of these, or 43, are expected to be albinos, and there are 

 actually 43 of this sort. That the observed and the theoretical results 

 should closely approximate was to be expected, but their exact agree- 

 ment to a unit is, of course, more or less fortuitous. 



Still other combinations of three alleloraorphic characters are possible. 

 Batesoii (: 03" ) has indicated one such with respect to comb character 

 among fowls. The characters " rose comb " (R) and " pea comb " (I*) 

 are each dominant with respect to the character "smooth coml) " (S). 

 A " pea comb" is defined as "a comb consisting of three fairly regular 

 longitudinal ridges, along each of which are several more or less lumpy 

 tubercles." "A rose comb consists of a great number of papilliform 

 elevations, standing in the same horizontal plane. It is wide in the 

 middle, and contracts to a point or ' pike ' behind." Two heterozygotes, 

 the one by parents having respectively pea comb and smooth or single 

 comb, the other by parents having respectively rose comb and smooth 

 comb, were bred together. The two heterozygotes thus had each a 

 different dominant comb character, though both had the same recessive 

 character. The result of their union was the production of four sorts of 

 young. The following scheme shows the nature of the unions : 



R 4- S = gametes of rose (smooth) fowl, 

 P + S = " pea (smooth) " , 



F 2 : RP -f- PS + RS + SS == possible unions. 



These four classes were found to be actually present in Fo, each well 

 characterized. The RP combination was peculiar, resembling the 

 " walnut" comb of some Malayan fowls. In generation F3, the results 

 of which are not fully published as yet, Bateson found evidence of imper- 

 fect segregation in some of the RP class. 



A series of somewhat similar experiments has been made by the 

 writer, using mice. The character common to both heterozygotes was 

 that of total pigmentation, derived from a cross with the wild gray house 

 mouse. The other two characters were in the one case complete albin- 

 ism, and in the other partial albinism, the latter from a black-white male 

 known to be pure with respect to that character. The following scheme 

 will serve to show the derivation of the two sorts of heterozygotes 

 used ; 



