which descend from them, provided the changes acquired are common to the two sexes, or to those which have produced new individuals.'1 Still, these two opposite opinions, both of which may be supported by facts, can be reconciled if we bear in mind that there are modifications which, by their very nature, are in antagonism with everything around them, and for which, in consequence, the conditions of existence grow more and more difficult; just as there are others which, when in conformity with everything around them, may become permanent by either natural or artificial selection : so that all things conspire to blot out the former class of modifications, and to perpetuate the latter. We shall meet this difficulty again, when treating of psychological heredity, and will there consider it more fully. We have now to speak of the last form of heredity—that of disease. This seems to have been observed from the foundation of the art of medicine-in all times, in every land, and in every nation. Even the Greek physicians recognized hereditary diseases (νόσοι κληρονομίκαι). And yet in modern times the heredity of disease has given rise to all manner of debates among medical men. It would be beyond our subject, and beyond our power, to discuss this point. It is enough to say that the question appears to be substantially settled by the fact that the sturdiest opponents of morbid heredity admit, if not the heredity of disease itself, at least the heredity of a disposition to it. In Dr. Lucas's work on Heredity will be found facts of all kinds, sufficiently numerous and sufficiently clear to warrant a conclusion. This hasty physiological sketch will show that the law of heredity influences every form of vital energy—a fact which is generally known and admitted. Is the same to be said with regard to the psychological aspect of the question? This we propose now to consider, and to begin with the study of the facts. 1 In regard to the physiological side of this controversy, see the Bulletins de la Société d'Anthropologie, tome i. p. 339, and particularly p. 551, seq.; tome ii., De l'Hérédité des Anomalies. CHAPTER I. HEREDITY OF INSTINCTS. I. WHEN We speak of instinct, our first difficulty is to define the term. Not to enumerate here all the various significations of the word as used in ordinary language, it is employed in at least three different senses even by naturalists and philosophers, whose language has to be more precise than that of other people. Sometimes instinct is intended to signify the automatic, almost mechanical, and probably unconscious action of animals, in pursuance of an object determined by their organization, and specific characters. Again, instinct is made synonymous with desire, inclination, propensity; as when we speak of good or evil instincts, a thievish or murderous instinct. Finally, we sometimes comprise under the term instinct all the psychological phenomena occurring in animals, and all forms of mental activity inferior to those of man. This latter signification of the word is plainly the result of our unwillingness to attribute intellect to brutes; and thus, contrary to all reason, we confound with blind and unconscious impulses the conscious acts which every animal performs under the guidance of its individual experience,1 and which, consequently, are analogous to those which, in our own case, we call intelligent or intellectual acts. Although, in our opinion, instinct and intelligence are one and the same, as we will try hereafter to show, and though the difference between them is one not of kind, but only of degree; still we will employ the word instinct here in its first signification only which alone we hold to be exact and in conformity with etymology. We must, for the sake of greater precision, begin with a good definition of this term; but, unfortunately, no such definition has yet 1 For instance, the act performed by a dog carried far from his home, when from among a score of roads he selects the one which will bring him back. been found. Still we may, with a contemporary German philosopher, define instinct to be an act conformed to an end, but without consciousness of that end ;'1 or we may say, with Darwin, that 'an action which we ourselves should require experience to enable us to perform, when performed by an animal, more especially by a very young one, without any experience, and when performed by many individuals in the same way without their knowing for what purpose it is performed, is usually said to be instinctive.' 2 If, instead of defining instinct, we endeavour to determine its characteristics, not one of which perhaps is absolutely certain and unquestioned, we find a general agreement as to the following: Instinct is innate, i.e. anterior to all individual experience. Whereas intelligence is developed slowly by accumulated experiences, instinct is perfect from the first. The duckling hatched by a hen makes straight for the water; the squirrel, before it knows anything of winter, lays up a store of nuts. A bird hatched in a cage will, when given its freedom, build for itself a nest like that of its parents, out of the same materials, and of the same shape. Intelligence gropes about, tries this way and that, misses its object, commits mistakes and corrects them: instinct advances with a mechanical certainty. Hence comes its unconscious character; it knows nothing either of ends, or of the means of attaining them; it implies no comparison, judgment, or choice. All seems directed by thought, without ever arriving at thought; and if this phenomenon appear strange, it must be observed that analogous states occur in ourselves. All that we do from habit—walking, writing, or practising a mechanical art, for instance-all these, and many other very complex acts, are performed without consciousness. Instinct appears stationary. It does not, like intelligence, seem to grow and decay, to gain and to lose. It does not improve. it does not remain perfectly invariable, at least it varies only within very narrow limits; and though this question has been warmly debated in our day, and is yet unsettled, we may yet say that in instinct immutability is the law, variation the exception. 1 Hartmann, Philosophie des Unbewussten, p. 54. Berlin, 1869. If |