614 



THE AMERICAN NATURALIST [Vol. XLII 



In a letter to the writer he states that in a solution of potash 

 the yellow pigment disappears very quickly, the brown some- 

 what slowly, while the black disappears only after a much longer 

 interval. My interpretation of Noorduijn 's results is that yellow 

 and cinnamon color characters in canaries are probably simple 

 Mendelian characters (unit characters), while black is due to the 

 meeting of two Mendelian factors one of which is correlated with 

 cinnamon and the other with yellow. The case is probably more 

 complex than here indicated, for some of the results indicate the 

 presence of factors in addition to those here assumd. The prin- 

 cipal results can now be explained by assuming that C (cin- 

 namon or brown) and Y (yellow) are independent of each other, 

 and that the female sex element (F) is paired with Y. Noor- 

 duijn 's four cases are: 



I. Cc? X G (green or green variegated) females gives GJ 1 

 and C$. This cross sometimes gives G$'s but never C<$. 



II. X C$ gives both sexes G. 



III. Cc?XY? gives GJ and C$. Also sometimes G$ but 



never CJ. 



IV. YJ 1 X C? gives both sexes G. 



In the above no account is taken of variegation, which Daven- 

 port has shown to be itself a Mendelian character. 7 The Mende- 

 lian formulas for Noorduijn 's four cases now become (remember- 

 ing that when C and Y occur in the same bird the color is green 

 or green variegated) . 



I. CCyy X CCFy = CCFy + CCYy. 



C? Ga- 

 ll. CCYY X CCFy = CCFY + CCYy. 



G$ GJ 1 



III. CCyy X ccFY = CcFy -f CcYy. 



C? G<? 



IV. ccYY X CCFy = CcFY + CcYy. 



G? Grf. 



This does not account for occasional green females from crosses 

 I and III, from which fact additional factors not here considered 

 are indicated; but the formula? indicate quite clearly that the 

 sex element is paired with yellow coat color, or possibly with one 

 faetor of this color. This assumption is confirmed by Noor- 

 duijn 's statement that yellow males tend to impress their color 



