IV. Two Contemporaneous Doctrines: Mechanism, which reduces PAGE V. Is the Problem of the Relations between Physics and Morals a PSYCHOLOGICAL AND PHYSIOLOGICAL HEREDITY, I. Possible Hypotheses as to the Relations between these two Heredities. Is Psychological Heredity the Cause of Phy- siological Heredity? Is Physiological Heredity the Cause of II. Can Heredity become a Means of Selection, by Accumulating Slight Differences? Consanguineous Marriages. Half-breeds: THE PSYCHOLOGICAL CONSEQUENCES OF HEREDITY. I. Part played by Heredity in the Genesis of Instincts Part played by Heredity in the Genesis of Intelligence. Are the Forms of Thought the Result of Hereditary Accumulation? New Form of the Problem of the Origin of Ideas Part played by Heredity in the Genesis of Moral Ideas. Morals HEREDITY. INTRODUCTION. PHYSIOLOGICAL HEREDITY. HEREDITY is that biological law by which all beings endowed with life tend to repeat themselves in their descendants: it is for the species what personal identity is for the individual. By it a groundwork remains unchanged amid incessant variation; by it Nature ever copies and imitates herself. Ideally considered, heredity would simply be the reproduction of like by like. But this conception is purely theoretical, for the phenomena of life do not lend themselves to such mathematical precision : the conditions of their occurrence grow more and more complex in proportion as we ascend from the vegetable world to the higher animals, and thence to man. Man may be regarded either in his organism or in his dynamism in the functions which constitute his physical life, or in the operations which constitute his mental life. Are both of these forms of life subject to the law of heredity? are they subject to it wholly, or only in part? and, in the latter case, to what extent are they so subject? The physiological side of this question has been diligently studied, but not so its psychological side. We propose to supply this deficiency in the present work. But the hereditary transmission of mental faculties-considered in its phenomena, its laws, its consequences, and especially in its causes-is so closely connected with physiological heredity, that we are compelled to B consider this latter subject at the outset. This we will do very briefly, referring the reader for fuller details to special treatises. It will suffice to show, by means of a few definite and well-ascertained facts, that heredity extends over all the elements and functions of the organism; to its external and internal structure, its maladies, its special characteristics, and its acquired modifications. The first thing that attracts the attention, even of the unobservant, is the heredity of the external structure. This is a fact of everyday experience, and nothing is more common than to hear that such and such a child is the image of its father, mother, or grandparents. Hereditary influence may manifest itself in the limbs, the trunk, the head, even in the nails and the hair, but especially in the countenance, expression, or characteristic features. This is an observation made by the ancients; hence the Romans had their Nasones, Labeones, Buccones, Capitones, and other names, derived from hereditary peculiarities. According to Haller, the Bentivoglios had on their bodies a slightly prominent tumour, transmitted from father to son, which warned them of changes in the weather, and which grew larger whenever a moist wind was coming. The resemblance may be so close as to give rise to doubts concerning personal identity, or at once to betray parentage. Ten years before his death a singer at the opera, named Nourrit, appeared on the stage with one of his sons, who had inherited his physical constitution as well as his pleasing voice; and in a play with a plot like that of the Menæchmi, the extraordinary resemblance of the son to the father added a hundred-fold interest to the endless misunderstandings with which the play was filled.1 These hereditary resemblances have sometimes led to the most unexpected and most romantic adventures, so that it is not surprising that Marryat has turned them to account in his novel, 'Japhet in Search of a Father. It is still more singular that this resemblance between parents and children may undergo such metamorphoses as shall cause the child to resemble at one time the father, and at another the 1 P. Lucas, Traité Physiologique et Philosophique de l'Hérédité Naturelle, vol. i. p. 195. mother. Girou de Buzareingues, in his work De la Génération, containing some curious facts observed by him, tells us that he knew two brothers who in early life resembled their mother, while their sister resembled the father. These resemblances were such as to strike all who saw them. 'But now,' says he, and ever since their youth, the two boys resemble the father, while the daughter has ceased to be like him.' This same author was led, in consequence of numerous observations, to believe that changes of this kind are more frequent and more thorough in the case of boys than in that of girls. The system of intentional and conscious selection has been applied even to man. Frederick William I., the father of Frederick the Great, who was noted for his love of colossal men, dealt with his regiment of giants as stock-breeders deal with their cattle. He would not allow his guards to marry women of stature inferior to their own. Haller used to boast of his 'belonging to one of those races whose members, by reason of their imposing stature, seem born to rule other men.' Heredity may be also traced in all that concerns the complexion of the skin, and the shape and size of the body. Thus, so truly is obesity the result of an organic predisposition, that it has often been known to make its appearance amid privations, and under all the disadvantages of hard labour and poverty. Heredity influences the internal conformation no less than the external structure. Nothing is more undisputed than the heredity of the form, size, and anomalies of the osseous system; and universal everyday experience proves the heredity of all the proportions of the cranium, thorax, pelvis, vertebral column, and the smallest bones of the skeleton. Even the heredity of excess or defect in the number of the vertebræ and the teeth has been ascertained. (Lucas.) The circulatory, digestive, and muscular systems obey the same laws which govern the transmission of the other internal systems of the organism. There are some families in which the heart and the size of the principal blood-vessels are naturally very large; others in which they are comparatively small; and others, again, which present identical faults of conform ation. Lastly—and this is a point that more nearly concerns us— heredity regulates the proportions of the nervous system. It is |