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THE AMERICAN NATURALIST [Vol. XLVIII 



race and as a mutation or unit-character variation, retro- 

 gressive in nature {i. e., due to loss of some normal con- 

 stituent from the germplasm) . Each is a simple Mende- 

 lian recessive character in crosses with wild race, and 

 with certain at least of the tame varieties. The two varia- 

 tions have not as yet been combined by intercrossing, but 

 this will be attempted soon and, I doubt not, with entire 



My first information about the new variations was 

 obtained from Fur and Feather, the official organ of the 

 English fanciers, in which appeared advertisements of 

 "the new variety" of black-eyed yellow rat. Now as 

 long ago as 1903 Bateson had commented on the singular 

 absence of a "yellow" variety among rats, noteworthy 

 because nearly all mammals kept in captivity have such 

 varieties ; and I have since been bold enough to publish 

 some speculations as to why this variation had not made 

 its appearance. Consequently I was much excited to 

 learn that it actually had appeared. Miss M. Douglas, 

 one of the editors of Fur and Feather, and secretary of 

 the National Mouse and Rat Club (of England) very 

 kindly answered my inquiries about the new varieties and 

 put me in communication with the ''originators," who 

 have uiven so clear and full accounts of their procedure 

 in establishing the new varieties that even the genetic be- 

 havior of the variations is fairly certain, though I pur- 

 pose to confirm this fully with experiments which are 

 already in progress. 



The pink-eyed variation made its* appearance first, so 

 far as known, about 1910 or 1911, but it had probably 

 been in existence for some time and become rather widely 

 diffused throughout the central part of England, for at 

 about the same time pink-eyed wild rats were caught at 

 or near Preston and at Chesterfield, cities some 65 miles 

 apart. I am informed that Mr. T. Robinson at Preston 

 and Mr. W. E. Marriott at Chesterfield independently 

 established the '-pink-eyed fawn" variety, or what would 

 better be called the pink-eyed agouti variety, since appar- 



