_Professor of Statistics in the Royal University of Cagliari, Italy._ Tables of mortality relating to human beings with classification as to age, when compared with similar statistics relating to the equine species, show that man during the period of development has a much heavier death-rate. It is not possible to say whether in their natural state the higher kinds of animals possess a higher or lower death-rate during the period of development than when under domestication, but the second of the alternatives seems more likely. It remains to be determined whether the heavy death-rate during development which the human race shows in the comparison is a distinctive natural characteristic belonging to it, or whether it is rather the result of the more or less artificial circumstances in which man is born and reared. The human race differs as regards reproduction and the rearing of its offspring from the higher species of animals in their natural state, chiefly in three ways: (_a_) In the case of the human race reproduction takes place at all times of the year, whilst the higher animals have one single period for reproducing, or, in some cases, two or three periods; (_b_) animals reproduce as soon as the organism becomes capable of reproduction, whilst in civilised human races as a rule a longer or shorter period elapses between the time when the individual becomes capable of reproduction and the time he actually begins to reproduce; (_c_) in civilised man the development of altruistic sentiments protects weak and sickly persons from the eliminating action of natural selection, and often enables them to take part in the procreation of future generations. The paper of A. has for its object to examine closely these three arguments based upon very extensive data taken partly from demographic statistics and partly from researches made personally by him or which he caused to be made, especially in the Municipal Statistical Offices of Rome and Cagliari, and in the Obstetrical Clinic of Bologna. The principal results are here indicated. A. The rule of a greater number of conceptions in Spring observed in temperate regions suffers notable exceptions in tropical and arctic regions. Hence there is a weakening of the idea that in it one should recognise the atavistic heritage of a special season for reproduction which the human race had originally shown, analogous to what one finds to-day in many species of animals. On the other hand, neither the frequency of multiple births, of miscarriages, or of stillbirths, nor the length of life of offspring nor their intellectual capacity show any correlation whatever with the season of conception. The frequency of stillbirths, however, and the length of life of the offspring show a clear correlation with the season of birth, in the sense that those born in temperate seasons show a lower rate for stillbirths and a greater length of life.