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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, &c., 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.

OPERCULUM A calcareous plate employed by many Mollusca to close the aperture of their shell. The opercular valves of Cirripedes are those which close the aperture of the shell.

ORBIT The bony cavity for the reception of the eye.

ORGANISM An organised being, whether plant or animal.

ORTHOSPERMOUS A term applied to those fruits of the Umbellif erae which have the seed straight.

OSCULANT FORMS or groups apparently intermediate between and connecting other groups are said to be osculant.

OVA Eggs.

OVARIUM or OVARY (in plants) The lower part of the pistil or female organ of the flower, containing the ovules or incipient seeds; by growth after the other organs of the flower have fallen, it usually becomes converted into the fruit.

OVIGEROUS Egg-bearing.

OVULES (of plants) The seeds in the earliest condition.

PACHYDERMS A group of Mammalia, so called from their thick skins, and including the Elephant, Rhinoceros, Hippopotamus, &c.

PALÆOZOIC The oldest system of fossiliferous rocks.

PALPI Jointed appendages to some of the organs of the mouth in Insects and Crustacea.

PAPILIONACEÆ An order of Plants (see Leguminosæ). The flowers of these plants are called papilionaceous, or butterfly-like, from the fancied resemblance of the expanded superior petals to the wings of a butterfly.

PARASITE An animal or plant living upon or in, and at the expense of, another organism.

PARTHENOGENESIS The production of living Organisms from unimpregnated eggs or seeds.

PEDUNCULATED Supported upon a stem or stalk. The pedunculated oak has its acorns borne upon a footstalk.

PELORIA or PELORISM The appearance of regularity of structure in the flowers of plants which normally bear irregular flowers.

PELVIS The bony arch to which the hind limbs of Vertebrate animals are articulated.

PETALS The leaves of the corolla, or second circle of organs in a flower. They are usually of delicate texture and brightly coloured.

PHYLLODINEOUS Having flattened, leaf-like twigs or leafstalks instead of true leaves.

PIGMENT The colouring material produced generally in the superficial parts of animals. The cells secreting it are called pigment-cells.

PINNATE Bearing leaflets on each side of a central stalk.

PISTILS The female organs of a flower, which occupy a position in the centre of the other floral organs. The pistil is generally divisible into the ovary or germen, the style and the stigma.

PLACENTALIA, PLACENTATA, or PLACENTAL MAMMALS See