Some echo of the vital rhythm which pervades not merely the generations of animals, but the seasons and the stars, emerges sometimes in consciousness; on reaching the tropics in the mortal ecliptic, which the human individual may touch many times without much change in his outer fortunes, the soul may occasionally divine that it is passing through a supreme crisis. Passion, when vehement, may bring atavistic sentiments. When love is absolute it feels a profound impulse to welcome death, and even, by a transcendental confusion, to invoke the end of the universe.[B] The human soul reverts at such a moment to what an ephemeral insect might feel, buzzing till it finds its mate in the noon. Its whole destiny was wooing, and, that mission accomplished, it sings its _Nunc dimittis_, renouncing heartily all irrelevant things, now that the one fated and all-satisfying good has been achieved. Where parental instincts exist also, nature soon shifts her loom: a milder impulse succeeds, and a satisfaction of a gentler sort follows in the birth of children. The transcendental illusion is here corrected, and it is seen that the extinction the lovers had accepted needed not to be complete. The death they welcomed was not without its little resurrection. The feeble worm they had generated bore their immortality within it. The varieties of sexual economy are many and to each may correspond, for all we know, a special sentiment. Sometimes the union established is intermittent; sometimes it crowns the end of life and dissolves it altogether; sometimes it remains, while it lasts, monogamous; sometimes the sexual and social alertness is constant in the male, only periodic in the female. Sometimes the group established for procreation endures throughout the seasons, and from year to year; sometimes the males herd together, as if normally they preferred their own society, until the time of rut comes, when war arises between them for the possession of what they have just discovered to be the fair. [Sidenote: Structure the ground of faculty and faculty of duty.]