[Histological and ultrastructural study of the gonad of Helix aspersa Müller at hatching].

The gonad of young Helix aspersa, studied by light and electron microscopy during the first post-hatching week, showed a compact structure. Eventually, a lumen appeared as the cells moved apart. The gonad was composed of stem and germinal cells. The latter cells were represented by primordial germ cells and oocytes. With our method of rearing, the female germinal line differentiated first.