Thus, the ovum, active in the nucleus, its essential principle, is superficially passive; its mass, closed upon itself, compact in itself, evokes the nocturnal heaviness and repose of the in itself: the ancients visualized the closed world in the form of a sphere or opaque atom; immobile, the ovum waits; by contrast, the open sperm, tiny and agile, embodies the impatience and worry of existence.