ii6 Yellow Rabbits [ch. 



When the hair of the wild house-mouse, for instance, is 

 examined microscopically three kinds of pigment-granules 

 can be distinguished, black, chocolate, and yellow. As 

 Miss Durham pointed out (lo, p. 72), in a solution of potash 

 the yellow granules dissolve at once ; the chocolate dissolve, 

 but more slowly ; the black not at all. The pigments may 

 co-exist in the same parts of a hair, but in the wild "grey" 

 or agouti colour there are bands in the individual hairs, 

 where only yellow pigment can be seen. 



The black mouse has black and also chocolate pigment, 

 but no yellow. The chocolate has chocolate alone. 



The yellow mouse may have exclusively yellow pig- 

 ment, but in some yellows heterozygous with black, granules 

 of the other pigments may be mixed with the more abundant 

 yellow ones. 



In the blue, the silver- fawn and the cream, the pigments 

 are as in the black, the chocolate, or the yellow, respec- 

 tively, but the number of granules is fewer, giving the well- 

 known appearance of dilution in colour. 



The colours of rats, rabbits, guinea-pigs and horses, 

 appear to be similarly made up of three presumably com- 

 parable sets of pigments. There are differences however 

 both in the number of distinct pigmented types which exist, 

 and in their genetic behaviour. 



Rats. 



In rats the only colours known are agouti, and black. 

 Both types contain chocolate pigment as well as black, and 

 agouti also contains yellow pigment ; but no distinct choco- 

 late or yellow varieties are known, and none of the dilute 

 forms (blue, &c.) have been recorded. 



Rabbits. 



Of the cases in rodents where yellow exists as a separable 

 variety that of the rabbit is the simplest. Numerous 

 colour-types of the rabbit are known, but in our present 

 inquiry we are immediately concerned with the following : 

 I. Agouti, or wild grey, 2. Black, 3. Yellow. The question 

 whether a chocolate rabbit can be formed is important. It 

 appears that no such type is known to fanciers but Mr 

 Punnett saw, in the possession of a French breeder, rabbits 



