60 MENDELISM CHAP. 



two parents. But in other cases the nature of the rever- 

 sion may be more complicated owing to a larger number 

 of factors being concerned, though the general princi- 

 ple remains the same. Careful breeding from the rever- 

 sions 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 (PL I., 2). The Dutch rabbit is another 

 well-known breed. Generally speaking, the anterior por- 

 tion of the body is white, and the posterior part coloured. 

 Anteriorly, however, the eyes are surrounded by coloured 

 patches extending up to the ears, which are entirely col- 

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

 PL 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 ex- 

 periments about to be described a yellow Diitch rabbit 

 was crossed with a Himalaya. The resuk was a reversion 

 to the wild agouti colour (PL I., 3). Some of the F] in- 

 dividuals showed white patches, while others were self- 

 coloured. On breeding from the FI animals a series of 

 coloured forms resulted in F 2 . These were agoutis, blacks, 

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

 the fancy (PL L, 4-7). In addition to these appeared 

 Himalayans with either black points or with lighter brown- 



