TABLES. 121 



rough we find a primary unit difference, a modifying factor, imperfect 

 dominance in the effects of the latter, effects of residual heredity, and 

 probably some non-heritable variation. In the series from red through 

 yellow and cream to white we find multiple allelomorphs, imperfect 

 dominance, and small effects due to residual heredity. In the series 

 black through sepia to white, we find independent factors, multiple 

 allelomorphs which show imperfect dominance, and rather prominent 

 effects due to residual heredity and to age. This last series is interesting 

 as at least a close parallel in appearance to the series of variations in 

 human hair — black, brown, tow-color, to white. Thus in each case a 

 complex of the most varied causes underlies an apparently simple 

 continuous series of variations. 



EXPERIMENTAL DATA. 



EXPLANATION OF TABLES 62 TO 137. 



Crosses 1 to 15 include all matings recorded by the writer which 

 involve the inheritance of agouti and in which at least one of the parents 

 had Cavia rufescens ancestry. A large part of the remaining crosses are 

 non-agouti by non-agouti, producing only non-agouti young. All the 

 young in which the agouti factor should produce a recognizable effect, 

 if present, are classified under the heads Lb, Tb, and Non, which mean 

 light-bellied agouti, ticked-bellied agouti, and non-agouti, respectively. 

 Most of these are the typical (black-red) light-bellied or ticked-bellied 

 agouti or black. Those which are not typical, e. g., brown-red agouti 

 light-belly, red-eyed sepia, etc., are described further under the column 

 "Remarks." Those young in which the agouti factor can produce no 

 visible effect, even though present (albinos, reds, yellows, and creams), 

 are described under the column "Unclassified." Thus the exact color 

 of every one of the young from each mating can be found from the 

 tables, with the exception that white and red spotting are not noted. 

 The matings in each cross are numbered in the first column. The 

 number, description, and descent of the mother and father are given in 

 the second and third columns, respectively. As in the case of the 

 young, black-red agouti light-belly or ticked-belly or black, depending 

 on the heading of the column, are understood where no description is 

 given. The descent is indicated in most cases by a reference to the 

 mating from which the animal was derived. Thus 36-4 means mating 

 4 of cross 36. In other cases the stock is indicated as BB or BW. The 

 symbol ArF 2 means F 2 from crosses of Arequipa cf 1002 with guinea- 

 pigs. In some cases merely the amount of Cavia rufescens blood is 

 given. Thus M49, in the first cross given, was an ordinary ticked- 

 bellied agouti from mating 9 of cross la. Referring to this mating, 

 we see that his parents were female 84, a black of BB stock, and male 

 All 21, a ticked-bellied agouti with T W Cavia rufescens blood. 



