Silvering (Si) and Diminution (Dm) of Coat Color of the Guinea Pig, and Male Sterility of the White or near-White Combination of These.

HE present paper is based on studies of the residual variability in the intenT sity of the colors due to the recognized genes in a largely self contained colony of guinea pigs. I t is convenient to recognize seven major series of colors, each varying from a pale color, barely distinguishable from white to full intensity, primarily in accordance with the combination of c alleles, but secondarily because of the genes to be considered in this paper. Empirical grades have been based on standard hair samples, chosen SO that each grade is barely distinguishable from the preceding, One series of such standards has been used for the eumelanic colors (black, sepia, brown) and another for the phaeomelanic ones (yellow). Table 1 is taken from a previous paper to show the average grades and the standard deviations for the seven main series of colors (columns) and the various combinations of c alleles (WRIGHT 1949). The standard deviations in Table 1 give an indication of the amount of residual variability in intensity but not fully. In describing these data, it was noted (WRIGHT 1949) “no dark eyed sepias from matings in this series of experiments have been excluded because their grades deviated unexpectedly much from the genotype which had to be assigned them. Thus a number of extremely light sepias of genotypes cdca and c‘p (grades 7 to 9) segregated out and are included. Matings of such animals were, however, made in a different series of experiments designed to analyze extreme dilution and thus their progeny and descendants are not included here.” The same procedure was followed with unexpectedly light yellows, especially of genotypes 2 c T , cV, cdc‘, and cap (grade 3 or less instead of the usual 4 or 5 ) . There were also unexpectedly light pale sepias known to be EBCppF by ancestry and breeding tests, but as low in intensity as 2 instead of the usual 8 to 13. In this case, it seemed best to exclude bodily a cluster of eight closely related matings in establishing the norm.