22 



INHERITANCE OF COAT-PIGMENTS AND COAT-PATTERNS 



To obtain averages for the entire series, with which the values for the 

 several groups might be compared, tables 5, 7, 9, and 1 1 have been combined 

 to form table 13, which accordingly shows the average degree of inheritance, 

 in the entire series, of head spots, shoulder spots, side spots, and rump 

 spots, respectively. Similarly, tables 6, 8, 10, and 12 have here been combined 

 in table 14, which accordingly shows in general to what extent paired spots 

 are inherited in the Dutch -marked series. 



A comparison of the inheritance coefficients (per cents) in corresponding 

 places of tables 5, 7, 9, and n shows remarkably little change from one 

 generation to another. Paired head spots are inherited in the four groups 

 in 85.7, 82.1, 86. 5, and 89.3 per cent of the cases, respectively, or in the series 

 as a whole, in 87 per cent of all cases (table 13, upper left-hand square). 

 Similarly, paired rump spots are inherited in the four groups in 7 1 .4, 80, 

 80.9, and 83.1 per cent of the cases, respectively, or in the series as a whole 

 (table 13) in 80.7 per cent of all cases. In both head and rump spots the 

 inheritance coefficients increase slightly with the progress of selection. 



Shoulder and side spots are so frequently lacking in the Dutch-marked 

 series that comparison of the per cents for presence of these pairs would 

 have little value; it is better to examine rather the per cents for absence 

 of these spots. Both shoulder spots are absent in the four groups in 58.5, 

 59, 41, and 42 per cent of the cases, respectively (a decreasing series) ; average 

 for the four groups, 46.3 per cent. Similarly, side spots are entirely wanting 

 in the several groups in 50, 34.7, 47-2, and 44.8 per cent, respectively (again, 

 on the whole, a decrease), the average for the four groups being 46 per cent. 



It is scarcely necessary to examine in detail other parts of the several 

 tables. They show conditions for the most part intermediate between those 

 seen in these extreme instances. 



Selection for presence of spots (head and rump) and for absence of spots 

 (shoulder) seems, in the same series of observations, to give contrary results. 

 These seemingly inconsistent facts are really not inconsistent. Spots 

 desired present and selected for have become slightly oftener present ; spots 

 desired absent and selected against have likewise become slightly oftener 

 present. Selection for particular spots has had nothing to do with bringing 

 about the result observed. The pigmentation has become somewhat more 

 extensive in the race, without our having consciously aimed to make it so. 

 Spots occur somewhat more numerously in the later than in the earlier gen- 

 erations of the series (see table 26). The increase, however, takes place no 

 oftener in regions where increase is desired (head and rump) than where it is 

 not desired (shoulder), or where its occurrence is a matter of indifference (side). 



This result shows the entire inefficiency of selection in guinea-pigs to fix 

 a coat-pattern which is dependent upon the distribution of pigment in par- 

 ticular spots upon the body. 



