150 BLASTOGENIC VARIATIONS. 



30 foals annually, but a dam only one, hence the pro- 

 duction of respectively 7, 8, and 9 standard performers 

 by three mares is very remarkable. Professor Pear- 

 son,* however, does not accept the high degree of pre- 

 potency which these figures seem to indicate. He 

 points out that the fact of certain sires producing such a 

 preponderance of standard performers is largely due to 

 their exceptional pedigrees. It is also due to the 

 second-rate stallions being given far less chance of pro- 

 ducing performers, in that the mares sent them are 

 often inferior, or past their most intense fecundity, as 

 well as being fewer in number. 



In discussing the law of heredity in the last chapter, 

 it was tacitly assumed that the heritage from each 

 parent was the same, or that both parents were equi- 

 potent. This does not seem to be necessarily the case, 

 however, as Professor Pearson finds that in man the 

 father is slightly prepotent over the mother for the off- 

 spring of both sexes, f Thus a determination of the 

 coefficient of correlation in respect of stature and of 

 head index, gave the following figures: 



Coeff. of correlation 



Father and son (Middle class English) .396 (for stature) 



" daughter " " " .360 " 



Mother and son " " " .302 " 



" daughter " " " .284 " 



" " son (N. American Indians) .370 (for head index) 



" daughter " " .300 " " 



The average correlation between stature of father 

 and of offspring was thus .378, and between that of 

 mother and of offspring .293, or 22.5 per cent. less. The 



* Nature, vol. Iviii. p. 292. 



f " Grammar of Science," p. 458. 



