‖n. [ NL. See Hetero-, and Nereis. ] (Zool.) A free-swimming, dimorphic, sexual form of certain species of Nereis. [ 1913 Webster ]

☞ In this state the head and its appendages are changed in form, the eyes become very large; more or less of the parapodia are highly modified by the development of finlike lobes, and branchial lamellæ, and their setæ become longer and bladelike. [ 1913 Webster ]

n.; pl. E. Nereids L. Nereides [ L. Nereis, -idis, Gr. Nhrei:`s Nhrhi:`s, Nhrhi:`dos, a daughter of Nereus, a nymph of the sea, fr. Nhrey`s Nereus, an ancient sea god; akin to nhro`s wet, Skr. nāra water, cf. Gr. na`ein to flow. ] 1. (Class. Myth.) A sea nymph, one of the daughters of Nereus, who were attendants upon Neptune, and were represented as riding on sea horses, sometimes with the human form entire, and sometimes with the tail of a fish. [ 1913 Webster ]

2. (Zool.) Any species of Nereis. The word is sometimes used for similar annelids of other families. [ 1913 Webster ]

n. (Zool.) Any annelid resembling Nereis, or of the family Lycoridae or allied families. [ 1913 Webster ]

‖prop. n.; pl. Nereides [ L. ] 1. (Class. Myth.) A Nereid. See Nereid. [ 1913 Webster ]

2. (Zool.) A genus, including numerous species, of marine chaetopod annelids, having a well-formed head, with two pairs of eyes, antennae, four pairs of tentacles, and a protrusile pharynx, armed with a pair of hooked jaws. [ 1913 Webster ]

n. pl. (Paleon.) Fossil tracks of annelids. [ 1913 Webster ]