56 MENDELISM CHAP. 



greater or less extent, but as its inheritance in this 

 set of experiments is complicated and has not yet 

 been worked out, we may for the present neglect it 

 and confine our attention to the coloured types and 

 to the Himalayans. The proportion in which the 

 four coloured types appeared in F 2 was very nearly 

 9 agoutis, 3 blacks, 3 yellows, and i tortoiseshell. 

 Evidently we are here dealing with two factors: (i) 

 the grey factor (G\ which modifies black into agouti, 

 or tortoiseshell into yellow ; and (2) an intensifying 

 factor (/), which intensifies yellow into agouti and 



Yellow X Himalayan 



Agouti X Agouti 



r~ ~r~ 



Agouti Yellow Black Tortoise Himalayan 



Shell 

 (27) (9) (9) (3) (16) 



tortoiseshell into black. It may be mentioned here 

 that other experiments confirmed the view that the 

 yellow rabbit is a dilute agouti, and the tortoiseshell 

 a dilute black. The Himalayan pattern behaves as 

 a recessive to self-colour. It is a self-coloured black 

 rabbit lacking a factor that allows the colour to 

 develop except in the points. That factor we may 

 denote by X, and as far as it is concerned the 

 Himalayan is constitutionally xx. The Himalayan 

 contains the intensifying factor, for such pigment 

 as it possesses in the points is full coloured. At 

 the same time it is black, i.e. lacking in the factor G. 

 With regard to these three factors, therefore, the con- 

 stitution of the Himalayan hggllxx. The last char- 



