author's abstract of this paper issued 

 by the nibliographic service, july 24 



FURTHER STUDIES OF COLOR MUTATIONS IN :\IICE 

 OF THE GENUS PEROMYSCUS 



F. B. SUMNER AND H. H. COLLINS 



TWO PLATES (nine FIGURES) 



INTRODUCTION 



The several sports or mutations to be considered in the present 

 paper have already been mentioned or discussed in previous 

 papers bj^ the senior author (Sumner, '17, '18, '20, '22), and two 

 of them — the 'yellow' and 'pallid' races — have been rather fully 

 described. We shall here report the results of later observa- 

 tions and breeding experiments upon these mice. Crosses 

 have been made between the chief mutant races, and their 'gen- 

 etic behavior' tested according to customary mendelian methods. 

 More accurate color determinations have been rendered possible 

 through the purchase by the Scripps Institution of an efficient 

 colorimeter. 1 In addition to this, we have thought it desirable 

 to publish for the first time colored illustrations of several of 

 the mutant strains. 



^ Reference is made to the Hess-Ives tint-photometer. The use of this instru- 

 ment for determining the color values of mammalian pelages has already been 

 briefly discussed by Sumner ('21). In using this apparatus, light reflected from 

 the object to be examined is viewed in juxtaposition to light from a pure white 

 block of magnesium carbonate, the two being seen through the same color screen. 

 Three of these color screens are employed in succession, these being of such wave 

 lengths as would give pure white light (or neutral gray) if the transmitted rays 

 were combined. In making the reading with each of these screens, the light 

 reflected from the 'magnesia' block is cut down by a diaphragm to a point at 

 which its intensity is exactly equal to that of the object to be examined. At 

 this point the two halves of the visual field are of equal illumination, and likewise 

 (owing to the color screen) are of the same color. The illumination of the entire 

 field is rendered homogeneous by a special series of rapidly rotating lenses, in 

 consequence of which the area of pelage under examination appears of an ab- 

 solutely uniform tint. Specially prepared flat skins are used, these being first 

 thoroughly cleaned in benzine to remove grease. 



289 



THE JOCRXAL OF EXPERIMENTAL ZOOLOGT, VOL. 36, NO. 3 



