Charles Darwin: The Origin of Species by means of Natural Selection

GLOSSARY 1. GLOSSARY OF THE PRINCIPAL SCIENTIFIC TERMS USED IN THE PRESENT VOLUME. (continued)

MONOCOTYLEDONS, or MONOCOTYLEDONOUS PLANTS.--Plants in which the seed sends up only a single seed-leaf (or cotyledon); characterised by the absence of consecutive layers of wood in the stem (endogenous growth), by the veins of the leaves being generally straight, and by the parts of the flowers being generally in multiples of three. (Examples, grasses, lilies, orchids, palms, etc.)

MORAINES.--The accumulations of fragments of rock brought down by glaciers.

MORPHOLOGY.--The law of form or structure independent of function.

MYSIS-STAGE.--A stage in the development of certain crustaceans (prawns), in which they closely resemble the adults of a genus (Mysis) belonging to a slightly lower group.

NASCENT.--Commencing development.

NATATORY.--Adapted for the purpose of swimming.

NAUPLIUS-FORM.--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 reptiles, either to moderate the effects of a strong light or to sweep particles of dust, etc., from the surface of the eye.

OCELLI.--The simple eyes or stemmata of insects, usually situated on the crown of the head between the great compound eyes.

OESOPHAGUS.--The gullet.

OOLITIC.--A great series of secondary rocks, so called from the texture of some of its members, which appear to be made up of a mass of small EGG-LIKE calcareous bodies.