— The earliest stage in the development of many Crustacea,

especially belonging to the lower groups. In this stage the animal has a short body, with indistinct indications of a division into segments, and three pairs of fringed limbs. This form of the common fresh-water CYCLOPS was described as a distinct genus under the name of NAUPLIUS.

NEURATION. — The arrangement of the veins or nervures in the wings of insects.

NEUTERS. — Imperfectly developed females of certain social insects (such as ants and bees), which perform all the labours of the community. Hence, they are also called WORKERS.

NICTITATING MEMBRANE. — A semi-transparent membrane, which can be drawn across the eye in birds and