Page:Popular Science Monthly Volume 60.djvu/232

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POPULAR SCIENCE MONTHLY.

simply suppose that each parentage produces one couplet of grown-up filials, an adult man and an adult woman.

The result is shown to the nearest whole per thousand in the diagram up to 'U and above' It may be read either as applying to fathers and their sons when adult, or to mothers and their daughters when adult, or, again, to parentages and filial couplets. I will not now attempt to explain the details of the calculation to those to whom these methods

PSM V60 D232 Standard eugenics scheme of descent.png

are new. Those who are familiar with them will easily understand the exact process from what follows. There are three points of reference in a scheme of descent which may be respectively named 'mid-parental,' 'genetic' and 'filial' centers. In the present case of both parents being alike, the position of the mid-parental center is identical with that of either parent separately. The position of the filial center is that from which the children disperse. The genetic center occupies the same position in the parental series that the filial center does in the filial series. 'Natural Inheritance' contains abundant proof, both observational and