THE FACTOR HYPOTHESIS AS APPLIED TO ANIM.\LS 389 



The factorial make-up of the various mice in Miss Durham's 

 experiments would, then, be represented as follows: 

 ^JCP = black 



BiCP =blue (dilute black) 

 6/CP= chocolate (absence of black) 

 biCP = silver fawn (dilute chocolate) 



The following experiments indicate the mode of heredity on the 

 factorial basis: 



1. P Black (3/CP)XSUver-fawn (biCP) 

 F, 100 per cent Black (BlCP-biCP) 



F, Black {BICP) Blue (BiCP) Chocolate (blCP) Silver-fawn 



(biCP) 

 9331 



2. P Blue (5CP)X Chocolate (bICP) 



F, 100 per cent Black (BiCP-blCP) 



Fa Black {BICP) Blue (BiCP) Chocolate (bICP) Silver-fawn 



(biCP) 

 9331 



3. P Blue (^iCP)X Silver-fawn (biCP) 

 Fx 100 per cent Blue (BiCP-biCP) 

 F, Blue (BiCP) Silver-fawn (hiCP) 



3 I 



DIFFERENT KINDS OF ALBINOS 



Any one of the color types mentioned, if lackin^: in the factor C. 

 *rill be an albino, though carrying the other factors for color. For 

 example, there may be a Black-albino (BIcP), a Blue-albino (BicP), 

 a Chocolate-albino (bIcP), or a Silver-fawn-albino (bicP). 



That color factors are present in albinos may be shown by the 

 following experiment. An albino had appeared in a Black stock and 

 was crossed with a Silver-fawn, thus: 



4. P Silver-fawn (^)/CP)X Albino extracted from Black (BIcP) 

 F, 100 per cent Black (biCP-BIcP) 



Black Blue Chocolate Albino-Black Silver-fawn 

 (BICP) (BiCP) (bICP) (BIcP) (biCP) 



27 9 9 9 3 



Albino-Blue Albino-Chocolate Albino-Silver-fawn 



(BicP) (bIcP) (bicP) 



