Xo. 625] PIXK-EYED SELF WHITE GEIXEA-PIGS 121 



diately started with this in view, but since there were 

 only three animals to work with at the start progress 

 was necessarily slow at first. 



In the meantime Detlefsen (1916) had described some 

 pink-eyed white mice carrying the color factor. He be- 

 lieved they were due to the combination of the dominant 

 self white condition and the pink-eyed, but in his paper 

 this was not fully demonstrated. 



Castle (1916) refers to two pink-eyed white guinea- 

 pigs, presumably albinos, which Avere born to pigmented 

 parents. The male parent was tested with true albinos, 

 but all of the eleven offspring obtained were pigmented. 

 Castle therefore supposes that the two pink-eyed white 

 offs]-)ring Avere not true allnnos, but " pink-and-red-eyed" 

 animals lacking the factor for the extension of black or 

 chocolate ])igiiK'iit. Tliis is undoubtedly the correct ex- 

 planation, as the ('vi(U'nce presented in this paper will 

 demonstrate, ('astlc, howt-vcr. must liavi- diseardi'd his 

 pink-eyed whites before h" realized iheir iniiortauce 

 since he makes no mention of testinu' them u-enet ieally. 



Before -oin- into farther detail it inav he well to do- 

 scrihe briefly the various faetors dir.rtly eoneerne.l in 

 the produetion of the pink-eyed self whites. S.mu." of 

 those indirectly coiicei-ned are also described in order to 

 give the proper orientation. 



Desciuption of Factors 



B, the factor for black ])ignu'ntation. When unmodi- 

 fied bv other factors hlack i.i-ment is found only 

 in thi' evelids. nianunae. external genitals and the 

 skin of the ears and feet. 



h, the factor f<.r choeoh'ite (<.r brown) ].iginentation. 



E, the faetor for extension of black or ehoc.late 

 thr.,u-hout the pigmented paH of the coat. The 

 nn])ii;numte,l parts are r,f (MUirs.' white. 



c", the partial ext.msion faetoi-. This faetor causes 

 hlack or chocolate to he only partially extended 

 and therefore to appear in l)lotclies, the remainder 



