Note:  Do not rely on this information. It is very old.

Nauplius

Nauplius, the name of one of the principal of larval forms of Crustacea. Unlike the adults, the body of the larva is not divided into a series of divisions or segments; it has, moreover, only three pairs of appendages, which correspond to the two pairs of feelers or antennae and the mandibles or jaws. Another difference from the adult is the possession of only a single eye in the middle line of the head instead of a pair placed one on either side. The name was given to this larva under the impression that it was a distinct animal, before its life-history was discovered. This form of larva is typical of the subdivision of the Crustacea known as the Entomostraca (q.v.); it occurs, however, in two members of the other group - the Malacostraca (q.v.), viz. the genera Euphausia and Pentcus, while in a third genus, Lucifer, there is an allied form known as the Meta-Nauplius, which differs from the nauplius by the presence of two additional pairs of limbs.