SEXUAL REPRODUCTION WITHOUT CROSS-COPULATION IN THE FRESH-WATER TRICLAD TURBELLARIAN, CURTISIA FOREMANII

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Abstract
1. Experiments are described in which freshly-hatched juvenile specimens of Curtisia foremanii have been isolated in individual culture dishes and their ability to produce offspring in the absence of cross-copulation established. Some lines of these cultures, each worm of known pedigree from the P1 generation, are now in the F3 generation after approximately 9 months. 2. In the course of the experiments, indications have been noted that litter-mate worms may differ in the rate at which they attain maturity (criterion: deposition of first cocoon) and in their reproductive potential, and that strain differences in these qualities also exist in worms of diverse ancestry. 3. Although other species of fresh-water triclad Turbellaria have been reported as depositing only infertile cocoons in isolation, the overall percentage of infertility in Curtisia cocoons produced by isolated individuals is only 12%. 4. It has thus been demonstrated that cross-copulation is not essential to sexual reproduction in this species. Indeed, copulation of Curtisia foremanii has never been observed in this laboratory, and the possibility is suggested that it may never occur in this species.

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