primitive of the animal instincts, and the most indispensable. Without it no animal species endowed in any degree with the power of self-movement and a faculty of intelligence could maintain itself even a short time. It rules the entire life of the animal. The same social development which ascribes the care of the intellectual faculties to particular classes and the practical movement to others, and produces in the first an elevation of the "spirit" over the coarse "matter," goes so far in the process of isolating the intellectual faculties that the latter, out of contempt for the "mechanical" action which serves for the maintenance of life, comes to despise life itself. But this kind of knowledge has never as yet been able to overcome the instinct of self-preservation, and to paralyse the "action" which serves for the maintenance of life. Nay, even a suicide may be philosophically grounded; we always in every practical act of the denial of life finally meet with disease or ddsperate social circumstances as the cause but not a philosophical theory. Mere philosophising cannot overcome the instinct of self-preservation.
But if this is the most primitive and widely-spread of all instincts, so is it not the only one. It serves only for the maintenance of the individual. However long this may endure, finally it disappears without leaving any trace of its individuality behind, if it has not reproduced itself. Only those species of organisms will assert themselves in the struggle for existence who leave a progeny behind them.
Now with the plants and the lower animals the reproduction is a process which demands no power of self-movement and no faculty of intelligence. That changes, however, with the animals so soon as the reproduction becomes sexual, in which two individuals are concerned, who have to unite in order to lay their eggs and sperm on the same spot outside of the body or to incorporate the sperm in the body of the individual carrying the eggs.
That demands a will, an impulse to find each other, to unite. Without that the non-sexual propagation cannot take place; the stronger it is in the periods
