Beschreibung:
<jats:p>A comparative description of the life cycle of Ancylus fluviatilis from the intermittent biotops in a calcareous stream of Provence and the life cycle of animals which live in permanent biotops is given. Animals estivation in intermittent biotops is analysed. Estival growth of their shell points out an immediate agreement between entrance or outlet of dormancy and disap¬ pearance or re-establishment of vital conditions for this species. The substrat works as sieve : only the smaller animals move between the stones and survive.</jats:p>