characteristic in. th e ancestry of either A or C, or again as to the chance of the characteristic arising as a congenital sport, qnite independently of any heredity. I t seems unlikely th a t the observation of rare and isolated cases of asserted telegony will lead to any very satisfactory conclusions, although a well-directed series of experim ents m ight undoubtedly do so. On the other hand, it is not impossible than an extensive and careful system of family measurements m ight bring to lig h t something of the nature of a telegonic influence in m ankind. If such a telegonic influence really exists, it may be supposed to act in at least two and, very possibly, more ways.
(а) There may be in rare and isolated cases some remarkable change produced in the female by m ating w ith a particular male, or some rem arkable retention of the male element.
(b) There may be a gradually increasing approxim ation of the female to the* male as cohabitation is continued, or as the female bears more and more offspring to the male.
I t is extrem ely unlikely th a t any system of fam ily measurements would suffice to bring out evidence bearing on (a). On the other hand, a closer correlation between younger children and the father, and a lesser correlation between younger children and the mother, as compared w ith the correlation between elder children and their parents m ight, perhaps, indicate a steady influence like (b) at work in mankind. Shortly, such m easurem ents m ight suffice to answer the question as to w hether younger children take more after their father and less after th eir m other th an elder children. W ithout hazarding any physiological explanation as to the mode in which telegonic influence can or does take place, we may still hope to get, at any rate, negative evidence as to a possible steady telegonic influence by an investigation of suitable family measurements.
(2) U nfortunately, the collection of family data is by no means an easy task, and to procure those head-measurements, which, I think, would be most satisfactory for the problem of heredity, would require a large staff of ready assistants, and could only be undertaken on the necessary scale by the action of some scientific society or public body. The data concerning 800 to 900 families which have been recently collected for me deal only with stature, span, and arm-length, which are measurable w ith more or less accuracy by the untrained observer, and are only suitable for more or less rough appreciations of hereditary influence. The numbers in each family measured were strictly limited, in order to remove the influence of reproductive selection from the determ ination of the correlation between parents and children, and the result of this lim itation has been that comparatively few couples of elder and younger brothers, and of elder and younger sisters are available. They were, indeed, collected in the
