The "Daphnia" reproductive system is parthenogenetic. The female daphnia produce eggs without mating. That means that their eggs can grow without being fertilized. The female daphnia carries its 50 or so eggs in the brood chamber, until they are ready to hatch. "Daphnia" can still mate, the only difference is that the “mated” eggs have an extra hard shell that can protect them from harsh conditions for a long time. These eggs are called cysts, and they can hatch when conditions are favorable again, which is usually around spring.