It is not by accident that inherited longevity in a family is associated with low mortality of its children. The connection between the two facts was first discovered by Mary Beeton and Karl Pearson in their pioneer work on the inheritance of duration of life. They found that high infant mortality was associated with early death of parents, while the offspring of long-lived parents showed few deaths in childhood. The correlation of the two facts was quite regular, as will be evident from a glance at the following tables prepared by A. Ploetz: LENGTH OF LIFE OF MOTHERS AND CHILD-MORTALITY OF THEIR DAUGHTERS. ENGLISH QUAKER FAMILIES, DATA OF BEETON AND PEARSON, ARRANGED BY PLOETZ Year of life in which mothers died At all 0-38 39-53 54-68 69-83 84 up ages No. of daughters 234 304 305 666 247 1846 No. of them who died in first 5 years 122 114 118 131 26 511 Per cent. of daughters who died 52.1 37.5 29.9 19.7 10.5 27.7 LENGTH OF LIFE OF FATHERS AND CHILD-MORTALITY OF THEIR DAUGHTERS Year of life in which fathers died At 0-38 39-53 54-68 69-83 84 up all ages No. of daughters 105 284 585 797 236 2009 No. of them who died in first 5 years 51 98 156 177 40 522 Per cent. of daughters who died 48.6 34.5 26.7 22.2 17.0 26.0 To save space, we do not show the relation between parent and son; it is similar to that of parent and daughter which is shown in the preceding tables. In making comparison with the 340 families from the Genealogical Record Office, above studied, it must be noted that Dr. Ploetz' tables include one year longer in the period of child mortality, being computed for the first five years of life instead of the first four. His percentages would therefore be somewhat lower if computed on the basis used in the American work. These various data demonstrate the existence of a considerable correlation between short life (_brachybioty_, Karl Pearson calls it) in parent and short life in offspring. Not only is the tendency to live long inherited, but the tendency _not_ to live long is likewise inherited. But perhaps the reader may think they show nothing of the sort. He may fancy that the early death of a parent left the child without sufficient care, and that neglect, poverty, or some other factor of euthenics brought about the child's death. Perhaps it lacked a mother's loving attention, or perhaps the father's death removed the wage-earner of the family and the child thenceforth lacked the necessities of life.