THE 



AMERICAN NATURALIST 



Vol. XLVIII February, 1911 No. 566 



SOME NEW VARIETIES OF RATS AND GUINEA- 

 PIGS AND THEIR RELATION TO PROBLEMS 

 OF COLOR INHERITANCE 



PROFESSOR W. E. CASTLE 



The marvelous color variation of the domesticated ani- 

 mals has been recognized as a capital illustration of evo- 

 lution from the time of Darwin to the present, and much 

 study has been devoted to the question of how it has taken 

 place. Nevertheless we have very little positive informa- 

 tion as to how existing color varieties originated, and 

 theories differ concerning the matter. 



It becomes therefore important to record carefully any 

 contemporary events which may throw light on the sub- 

 ject. This is my excuse for calling the attention of scien- 

 tists to the recent appearance in England of two new and 

 striking color variations of the common or Norway rat. 

 I say "appearance" advisedly for it is impossible to say 

 how long these variations may have been in existence 

 within the race, cropping out perhaps from time to time 

 sporadically. Certain it is, however, that they have only 

 quite recently come to the attention of "fanciers," who 

 have taken them up with great enthusiasm. 



The new varieties are known to the fancy as (1) pinJ:- 

 eyed yellow, fawn, or cream; and (2) black-eyed^ yellow, 



that each of the two variations has originated in the wild 

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