Vol. IX. October, igo-;. No. 5 



BIOLOGICAL BULLETIN 



STUDIES IN THE INHERITANCE OF COLOR 



PERCHERON HORSES. 



E. II. HARPER. 



I. THE INFLUENCE OF SELECTION AND INBREEDING UPON 



PREPOTENCY. 



The materials for this paper have been drawn from the records 

 of the American and French Percheron Horse Breeding Associ- 

 ations. The data obtainable from breeders' books have been 

 used extensively within recent years in the investigation of prob- 

 lems of heredity. The "Law of Ancestral Heredity" formu- 

 lated by Galton and revised by Karl Pearson is the foremost of 

 the deductions claimed as a result of the study of such data. 



The information furnished by the Percheron register is in 

 respect to color, sex and age, and the questions proposed in this 

 paper involve the three sorts of data available. Three questions 

 have been made the subject of investigation : (i) To what extent a 

 color which has been predominant in the breed in the past shows 

 any prepotency over a color which has been increased by 

 breeders' selection. The case with the Percherons is that gray 

 has been the predominant color, but black is on the increase. 

 (2) A second question has been raised as to normal inheritance 

 from parents of different ages, whether parents of greater age 

 influence the offspring to a greater extent, and whether there is 

 an optimum age of prepotency. (3) Whether either sex is pre- 

 potent over the other. 



At the outset of this investigation the writer started to test the 

 " Law of Ancestral Heredity " of Galton. To this end was col- 

 lected the complete ancestry of 179 individuals up to the third 

 ancestral generation, showing the colors of parents, grandparents 



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