Even active predators, however, also seem to spend a fair bit of time scavenging. Scavenging behavior is generally different from active predation because the proboscis is only rarely used. Instead, the worm simply ingests the food items directly with the mouth when scavenging. As with the flat worms above, most nemerteans show remarkable powers of regeneration, and nearly all species can regenerate at least the posterior portions of the body. If the pieces are extremely small a protective mucous cyst is often formed within which the new worm regenerates.
Larger pieces regenerate to form a complete worm without the protection of a cyst.
These animals typically have separate sexes, although sequential and even simultaneous hermaphrodites are known, and they typically spawn either freely into the water column, or in gelatinous masses of mucous produced by the mating worms. There are also some species which copulate and have internal fertilization, some species have only the male spawn in the mucous mass and the sperm find their way to the eggs within the female's body. Some species have the young develop, nourished by yolk, in egg masses, some develop in the water column, where they must feed to gain sufficient energy to metamorphose into the adult body form, others also develop in the water column, but are provisioned with yolk so that no feeding is required to complete development, and finally others develop directly within the female's body. Obviously the ease with which these animals may be raised in captivity depends on the reproductive mode of the species in question. Again, as in the flat worms above, some of these animals can be brilliantly colored and relatively benign additions to reef aquaria.