This fact, that in some measure the several instincts spring from a common ground of sentient life, that they each engage the individual as a whole, has serious consequences in the domain of habit, and therefore it counts for much in the growth of civilisation and in the everyday conduct of affairs. The physiological apparatus engaged in the functioning of any given instinct enters in part, though in varying measure, into the working of some or of any other instinct; whereby, even on physiological grounds alone, the habituation that touches the functioning of any given instinct must, in a less degree but pervasively, affect the habitual conduct of the same agent when driven by any other instinct. So that on this view the scope of habit, in so far as it bears on the instinctive activities, is necessarily wider than the particular concrete line of conduct to which the habituation in question is due. * * * * * The instincts are hereditary traits. In the current theories of heredity they would presumably be counted as secondary characteristics of the species, as being in a sense by-products of the physiological activities that give the species its specific character; since these theories in the last resort run in physiological terms. So the instinctive dispositions would scarcely be accounted unit characters, in the Mendelian sense, but would rather count as spiritual traits emerging from a certain concurrence of physiological unit characters and varying somewhat according to variations in the complement of unit characters to which the species or the individual may owe his constitution. Hence would arise variations of individuality among the members of the race, resting in some such manner as has just been suggested on the varying endowment of instincts, and running back through these finally to recondite differences of physiological function. Some such account of the instinctive dispositions and their relation to the physical individual seems necessary as a means of apprehending them and their work without assuming a sheer break between the physical and the immaterial phenomena of life. * * * * *