24 INHERITANCE OF COAT-PIGMENTS AND COAT-PATTERNS 



decrease of head spots, but they are on the whole less common in this series 

 than in Series D (81.1 and 87 per cent, respectively). 



However, shoulder, side, and rump spots become steadily less common in 

 the series, as a glance at table 25 will show. It is doubtful, however, whether 

 this is to be regarded as an effect of selection for elimination of specific areas. 

 It indicates, rather, a decrease in the average amount of pigmentation pos- 

 sessed by animals of this series, unwittingly brought about by the attempt 

 to eliminate most of the spots typically pigmented (compare table 27). It 

 is significant that head spots, though desired present and chosen equally 

 in Series D and in Series H, occur more commonly in the former than in the 

 latter. Animals of Series D are more extensively pigmented than those of 

 Series H (compare tables 26 and 27); the additional pigmentation may occur 

 in any of the typically pigmented areas, regardless of the areas which happen 

 to have been pigmented in the selected ancestors. 



Nevertheless, we find a more rapid falling off in the pigmentation of some 

 areas than in that of others. In Series H, shoulder spots fall off 16.9 per 

 cent; side spots, 7.3 per cent; and rump spots, 6.4 per cent; while head 

 spots, as already noted, show little change. Now, selection, it will be remem- 

 bered, was exercised for elimination of shoulder, side, and rump spots alike, 

 but for the retention of head spots. Accordingly we do not get changes 

 uniformly consistent with selection. Regardless of selection for specific 

 spots, we get, when the total amount of the pigmentation is decreasing, a 

 decrease most rapidly in shoulder spots, less rapidly in side spots, less rapidly 

 still in rump spots, while the head 1 spots are least affected. Conversely, in 

 a series in which the amount of pigmentation is increasing, the increase is 

 less marked in head than in rump spots, and less in side than in shoulder 

 spots. Thus, in Series D, head spots increase 3.6 per cent, rump spots, 

 II. 7 per cent; the change in side spots (entire absence) is 6.2 per cent, of 

 shoulder spots, 16.5 per cent. 



In further support of this same idea — that with increasing or decreasing 

 pigmentation changes occur more rapidly in some areas than in others, 

 irrespective of the particular spots borne by the ancestors — we may com- 

 pare the averages for Series D and H (tables 13 and 23). The dififerences 

 between the two series are, in frequencies of head spots, 5.9 per cent; of 

 side spots (absent), 20 per cent; of shoulder spots (absent), 25.4 per cent. 

 As regards rump spots, no comparable entries occur in either the first or 

 the last columns of tables 13 and 23, but an examination of the middle column 

 (2) in both tables indicates that the difference in rump spots in the two 

 series is about as great as in head spots. 



These facts are in harmony with an observation made in advance of the 

 statistical investigation, that the most persistent of all the pigmented areas 

 are the head spots, and next in order of persistency are the rump spots. 



