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THE AMERICAN NATURALIST [Vol. XLV 



service in estimating the desirability of individual 

 parents. 



By individual prepotency 2 we understand for present 

 purposes the phenomenon of certain individuals, or pairs 

 of individuals in bi-parental inheritance, being excep- 

 tional in their capacity for producing offspring of any 

 given characteristic. 



As used here the term prepotency is most general. It 

 implies nothing concerning the somatic similarity 3 of 

 parent and offspring and is in no way dependent upon 

 any theory of heredity. It merely expresses a fact well 

 known to practical breeders for half a century. . 



By a coefficient of individual prepotency one under- 

 stands a statistical constant which measures the degree 

 of superiority (with respect to the capacity for the pro- 

 duction of offspring of any desired type) of any single 

 parent or pair of parents. 



The fundamental papers are: 



Pearson, K., "On some Properties of the Hypergeometrical Series, and 

 on the Fitting of such Series to Observation Polygons in the Theory of 

 Chance," Phil. Mag., February, 1899, p. 239. 



Pearson, K., "On the Curves which are most Suitable for Describing 



pp. 17-17.3, 1906. 



Pearson, K, "Note on the Significant or Non-significant Character of 

 a Sub-sample drawn from a Sample," Biometrika, Vol. V, pp. 181-183, 

 1906. 



Pearson, K., " On a Coefficient of Class Heterogeneity or Divergence," 

 Biometrika, Vol. V, pp. 198-203, 1906. 



Tocher, J. F., "The Anthropometric Characteristics of the Inmates of 

 Asylums in Scotland," Biometrika, Vol. V, pp. 315-318, 1907. 



Tocher, J. P., "Pigmentation Survey of School Children in Scotland," 

 Biometrika, Vol. VI, pp. 143-146, 162-164. 



a The disadvantages of using a word which lias been so variously em- 

 ployed as prepotency are offset by keeping the terminology as simple as 



unambiguous wherever used. 



of the parents and their offspring must be taken into account. Prepotency 

 parents as expressed in their respective arrays of offspring. 



