T7 7 



INHERITANCE OF COLOR IN PERCHERON HORSES. -/ / 



In an appendix are added some further tabulations of the data 

 of Table I., testing those results by Galton's Law. 



The data given in Table I. were collected under the direction 

 of Prof. C. B. Davenport at Chicago, with a view to testing the 

 application of Galton's Law of Ancestral Heredity, but since the 

 manifest action of breeders' selection has vitiated the data for 

 deductions as to normal inheritance, for a series of generations, it 

 is not worth while to include here any consideration of Galton's 

 Law. 



I wish to thank Mr. S. D. Thompson, Secretary of the 

 Percheron Horse Breeders' Association, for access to unpub- 

 lished records. 



APPENDIX. THE DATA OF TABLE I. IN RELATION 

 TO GALTON'S LAW. 



It was stated at the outset of this paper that the results of 

 Table I. do not agree with Galton's Law of Ancestral Heredity, 

 showing an abnormal proportion of black offspring, a fact doubt- 

 less due to breeders' selection. The excess of blacks is clearly 

 seen by inspection without the use of Galton's method of calcu- 

 lation, since the per cent, of black offspring is greater than the 

 per cent, of black parents, and the latter are greatly in excess of 

 the number present in the two preceding generations. Galton's 

 method of calculation was applied to these data, but it is not 

 worth while to include those calculations here in view of the fact 

 that the manifest action of breeders' selection has vitiated the 

 data for deductions as to normal inheritance. The general result 

 of the calculations may be given, however. They were made 

 according to Galton's original method, not by Pearson's method 

 of correlation, by which he makes use of far more data than the 

 ancestry of 179 individuals would furnish. 



The results are briefly: Out of 179 offspring the number of 

 blacks calculated was 74, the actual number being 91. Of the 

 grays the number calculated was 77, the actual number was 64. 

 The bay-brown group exceeded calculations considerably, com- 

 prising the remaining 24 individuals. 



At the right in Tables XV.-XVI. are given the per cents, of 

 blacks and grays in the consecutive classes beginning with those 



