A mechanism for self-inhibition of population growth in the flatworm Mesostoma ehrenbergii (Focke).

By producing subitaneous eggs the rhabdocoel Mesostoma ehrenbergii may quickly increase the population size. The production of this kind of eggs by young worms is inhibited by the presence of adults in the culture medium. The inhibition is specific, and it is observed also if young and adult worms are not in direct contact, or if young worms are added to the water where adults had been previously kept: there is therefore evidence for a chemical mediator. The sensitivity to the inhibition occurs during the first five days after birth, with a maximum on the 2nd to 3rd day.