CHAP. VI REVERSION 55 



other cases the nature of the reversion may be more 

 complicated owing to a larger number of factors 

 being concerned, though the general principle remains 

 the same. Careful breeding from the reversions will 

 enable us in each case to determine the number and 

 nature of the factors concerned, and in illustration 

 of this we may take another example from rabbits. 

 The Himalayan rabbit is a well-known breed. In 

 appearance it is a white rabbit with pink eyes, but 

 the ears, paws, and nose are black (PI. I., 2). The 

 Dutch rabbit is another well-known breed. Generally 

 speaking, the anterior portion of the body is white, 

 and the posterior part coloured. Anteriorly, how- 

 ever, the eyes are surrounded by coloured patches 

 extending up to the ears, which are entirely coloured. 

 At the same time the hind paws are white (cf. 

 PI. I., i). Dutch rabbits exist in many varieties of 

 colour, though in each one of these the distribution 

 of colour and white shows the same relations. In 

 the experiments about to be described a yellow 

 Dutch rabbit was crossed with a Himalaya. The 

 result was a reversion to the wild agouti colour 

 (PI. I., 3). Some of the F^ individuals showed 

 white patches, while others were self-coloured. On 

 breeding from the F^ animals a series of coloured 

 forms resulted in F.^. These were agoutis, blacks, 

 yellows, and sooty yellows, the so-called tortoise- 

 shells of the fancy (PI. I., 4-7). In addition to these 

 appeared Himalayans with either black points or 

 with lighter brownish ones, and the proportions in 

 which they came showed the Himalayan character 

 to be a simple recessive. A certain number of the 

 coloured forms exhibited the Dutch marking to a 



