The goddess-worms (Family Nephtyidae) can be difficult to identify, especially the small species. To the casual observer they are easily confused with sea-nymphs, p. 144. This has been a problem since 1817, when the Genus Nephtys was established to include some species that had previously been thought to be sea-nymphs. Years later in 1850, the Class Nephthydea, possibly in reference to an Egyptian goddess, was created to include the Genus Nephtys. The present family spelling of Nephtyidae is correct, as the initial spelling for Nephtys takes precedence over the subsequent class spelling of Nephthydea, where the final h was purposely or otherwise included. However, this does explain why these worms have occasionally been misspelled as Nephthys. Species of goddess-worms have been reported to reach great lengths—up to 40 cm (16 in). As with most polychaetes, there are separate male and female goddess-worms. Little is known concerning their reproductive habits, other than that they broadcast gametes into the seawater. After external fertilization, the larvae spend some time as part of the planktonic community. The transformation from larvae to juveniles apparently does not occur until they have settled into the sediment.