Mathematical Contributions to the Theory of Evolution. 275 



first place with a view to the problem of heredity in the direct line, 

 and with no thought of their throwing any light on the problem of 

 telegony. That steady telegonic influence might be deduced from 

 such family data has only recently occurred to me, and I should now 

 hesitate to publish any conclusions on this subject, based on some- 

 what mixed and sparse returns, did I not consider that it may be a 

 long time before more extensive returns are available, and that the 

 publication of this method of dealing with telegony may induce others 

 to undertake the collection of a wider range of material. 



My own 800 family data cards did not provide a sufficiently large 

 number of either brother- brother or sister-sister couples to give a 

 strong hope of a difference between the correlation coefficients 

 sufficiently large as compared with its probable error to base any 

 legitimate conclusion upon. I, therefore, again borrowed from Mr. 

 Galton his 200 family data returns, and from these 1,000 families 

 was able to select 385 brother-brother pairs and 450 sister-sister 

 pairs. In these statistics each individual is only included in one 

 pair, and the difference in age between the elder and younger mem- 

 bers of each pair differs very widely from pair to pair. In some cases 

 there may be several years between the ages and several intervening 

 children ; in others the members of the pair may be successive 

 children following each other in successive years. In each case all 

 we can say is, that if there be a steady telegonic influence, the rela- 

 tion of the elder member to the parent will weigh down the same 

 scale, and in the final result we ought to find a distinctly greater or 

 less correlation, as the case may be. I think a more serious objection 

 to the data than the variation in the number of years between 

 fraternal pairs is the mixture I have made of data collected at 

 different periods and in somewhat different manners. My own data 

 are drawn, I think, from a wider class of the community than Mr. 

 Galton's. They are not exclusive of his class, but, I think, cover his 

 class, and go somewhat further down in the social scale. They suffice 

 to show that the means and variations change considerably from one 

 social stratum to another, and what is still more important that the 

 Galton-Functions or coefficients of correlation for heredity are far 

 from being constant even within the same race, as we pass from one 

 rank of life to a second. Thus, my means for stature in the case of 

 both fathers and mothers are upwards of ^ in. less than Mr. Galton's, 

 but my means agree fairly well with his results in the case of both 

 sons and daughters. There are also good agreements and somewhat 

 puzzling disagreements not only in the variations, but, above all, in 

 the coefficients of correlation for heredity. I reserve for the present 

 the full discussion of my heredity data, but I wish it to be quite 

 understood that my conclusions in this paper are based, not upon the 

 best possible data, e.g., measurements made on one class of the com- 



VOL. LX. Y 



