94 Life and Letters of Francis Galton 



breeding, that shall aflbrd a secondary focus of regression, and become the dominant one, if the 

 ancestral qualities that interfere with it be eliminated by sustained isolation and selection. 

 Then a new variety would, as I conceive, arise ; but into this disputable topic there is no need 

 to enter now." [See, however, my footnote, p. 79.] 



We now know that on the theory of multiple regression, this indefinite 

 regression has no existence; there is a slight regression in the first genera- 

 tion of breeding from the selected stock, but it ceases with this generation. 

 We have again in the cited passage evidence that Galton was obliged to 

 appeal to "sports" to account for evolutionary progress, because he had mis- 

 interpreted the theory of regression. If iv be the regression of the offspring 

 of the first generation of selected midparentage, the regression of the 

 offspring of parents of the first generation, who have also selected midgrand- 

 parents, is not to be taken w again. Thus the formulae, the numerical table 

 and the conclusions drawn from it in this paper are I think in error. But 

 the idea at the back of it that the more intense the selection, the more rapid 

 is the relative progress, is true ; as also the idea that there may in each case 

 be a limiting value. Probably no such continued selection is really feasible; 

 too many characters in the organism are highly correlated, so that if it were 

 possible to carry under conditions of viability an individual character to a 

 height much above the population mean, some one or other of the correlated 

 characters would be almost certain to be incompatible with the continued 

 efficiency of the organism in relation to its environment or its functions*. 



I have not recalculated Galton's table, because with the data at present 

 available, I am inclined to believe that selection for two or three generations 

 and then inbreeding would be followed, at any rate in some characters, by 

 a progression rather than a regression. In other words the strength of 

 inheritance is such that with a very brief period of selection followed by 

 isolation a continuous differentiation will proceed — so far as it is not checked 

 by a counter natural selection. This suggests that we may have to seek in 

 heredity itself for the basis of progressive evolution ; a variation maintained 

 for a couple of generations, followed by an isolation of the offspring, will 

 continue to progress. If this be true we surmount the difficulty of why 

 variations to which the environment is not hostile, or indeed may be 

 favourable when they are sufficiently developed, can reach the stage of 

 development at which they become important as a new factor of efficiency 

 in the individual. We see that it is not natural selection, but the mere 

 force of heredity, which leads in isolated groups to the genesis of variations 

 of sufficient importance to have survival value to the individual. We may 

 term this theory of the genesis of remunerative variations the "Heredity 

 Theory of Progressive Evolution." It seems at first sight in flat contradic- 

 tion to Galton's views on continuous regression when selection ceases, 

 unless the selection has led to the creation of a sport. Yet it really flows 



* Nor is this confined only to the functions of the individual, but may concern the functions 

 of other members of its race. Thus breeders of bull-dogs have gone on continuously selecting 

 the size of the head until the mortality of puppies and bitches at littering has become so serious 

 as to threaten even the survival of the breed. 



