favourable for reproduction, so much the sooner will it take place, so much the better will be the prospects of a progeny for the maintenance of the species. On the other hand, there is little prospect for those individuals and species in whom the impulse for self-reproduction is weakly developed. Consequently, from a given degree of the devlopment, natural selection must develop, through the struggle for life, an outspoken impulse to reproduction in the animal world, and evermore strengthen it. But it does not always suffice to the attainment of a numerous progeny. We have seen that in the degree in which self-movement and intellectual powers grow, the number of the germs which the individual produces, as well as its vitality, have a tendency to diminish. Also, the greater the. division of labour, the more complicated the organism, the longer the period which is requisite for its development and its attainment to maturity. If a part of this period is passed in the maternal body, that has its limits. Even from consideration of space this body is not in a position to bear an organism as big as itself; it must expel the young body previously to that. In the young animals, however, the capacities for self-movement and intelligence are the latest achieved, and they are mostly very weakly developed as they leave the protecting cover of the egg or the maternal body. The egg expelled by the mother is completely without motion and intelligence. Then the care for the progeny becomes an important function of the mother: the hiding and defence of the eggs and of the young, the feeding of the latter, etc. As with the impulse for reproduction, so is it with the love for the young; especially in the animal world the maternal love is developed as an indispensable means, from a certain stage of the development on, to secure the perpetuation of the species. With the impulse towards individual self-preservation these impulses have nothing to do; they often come into conflict with it, and they can be so strong that they overcome it. It is clear that under otherwise equal conditions those individuals and species have the best prospect of repro-
