Page:Proceedings of the Royal Society of London Vol 60.djvu/305

Rh selection, but why should this be expected to influence only the mother P The father of m any children remains equally influential, but the m other’s relation is weakened when we give w eight to the quantity not the relative ages of her children. This is not a steady telegonic influence, but a correlation between fertility and hereditary influence in m others, which if it could be verified by further observation, would undoubtedly be of high significance. I would accordingly suggest as a possible law of heredity, deserving careful investigation, that : Hereditary influence the fem ale varies inversely as fertility.

In my paper on “Reproductive Selection,” (‘Roy. Soc. Proc.,’ vol. 59, p. 301), I have pointed out the important evolutionary results which flow from a correlation between fertility and any inheritable characteristic. If a law of the above character should be established after further investigation, ic is conceivable that it may act as an autom atic check on the extreme effects of reproductive selection.

(iii) The above results give ns for practicable purposes a quite sufficiently close vfdue of the correlation between parents and sons, when the influence of reproductive selection is excluded. Judging from stature the correlation between sons and parents is very closely given by 0-41 ±0-03.

The adopted by Mr. Galton, may, I think, safely be increased by 25 per cent., and further, the assumption that collateral heredity is twice as strong as direct heredity must, I hold, be finally discarded, for no determ ination of the former has given such a high value as 0’82.

(5) Hitherto we have regarded only the coefficients of correlation, and considered them to measure the strength of the hereditary influence, but it must be remembered th at the means of elder and younger sons are not the same, and th a t there is another way of looking at the problem. W e may ask : Do younger or elder sons differ most from the stature of th eir father, and is the order altered in the case of the m other ?

If we neglect the influence of sexual selection (see “Contributions to Math. Theory of Evolution,” III, pp. 287—8) we have, if and hm be deviations of father and m other from th eir means, and M<. and My be mean heights of corresponding fraternities of elder and younger sons in inches :

M„ = 69-1494 + 0*428% +0-4374A*. My = 691948+ 0-4427/^+0-4488^.


 * Now the ratio of the mean heights of parents is 68-5740 : 63'3078 =