protozoëa

from The Century Dictionary.

• noun A copepod-like larval type which is found in a few of the higher Crustacea. It has a long, jointed abdomen without appendages, and it swims by means of the antennæ. Euphausia, Penæus, Lucifer, and Sergestes are known to pass through a free protozoëan stage, and Porcellana and Pinnixa hatch as protozoëas, but they escape from the protozoëan skin and become zoëas a few minutes after hatching.