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HYMENOPTERA.-An order of insects possessing biting jaws and

usually four membranous wings in which there are a few veins.

Bees and Wasps are familiar examples of this group. HYPERTROPHIED.—Excessively developed.

ICHNEUMONIDÆ.—A family of Hymenopterous insects, the mem

bers of which lay their eggs in the bodies or eggs of other

insects. Imago. The perfect (generally winged) reproductive state of an

insect. INDIGENS.—The aboriginal animal or vegetable inhabitants of a

country or region. INFLORESCENCE.—The mode of arrangement of the flowers of plants. INFUSORIA.-A class of microscopic Animalcules, so called from

their having originally been observed in infusions of vegetable matters. They consist of a gelatinous material enclosed in a delicate membrane, the whole or part of which is furnished with short vibrating hairs (called cilia), by means of which the animalcules swim through the water or convey the minute par

ticles of their food to the orifice of the mouth. INSECTIVOROUS.— Feeding on Insects. INVERTEBRATA, or INVERTEBRATE ANIMALS.—Those animals which

do not possess a backbone or spinal column.

LacuNÆ.—Spaces left among the tissues in some of the lower ani

mals, and serving in place of vessels for the circulation of the

fluids of the body. LAMELLATED.—Furnished with lamellæ or little plates. Larva (pl. LARVÆ).— The first condition of an insect at its issuing

from the egg, when it is usually in the form of a grub, cater

pillar, or maggot. LARYNX.—The upper part of the windpipe opening into the gullet. LAURENTIAN.-A group of greatly altered and very ancient rocks,

which is greatly developed along the course of the St. Laurence, whence the name. It is in these that the earliest known

traces of organic bodies have been found. LEGUMINOS Æ.—An order of plants represented by the common Peas

and Beans, having an irregular flower in which one petal stands up like a wing, and the stainens and pistil are enclosed in a sheath formed by two other petals. The fruit is a pod (or legume).

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LEMURIDÆ.—A group of four-handed animals, distinct from the

Monkeys and approaching the Insectivorous Quadrupeds in some of their characters and habits. Its members have the nostrils curved or twisted, and a claw instead of a nail upon

the first finger of the hind hands. LEPIDOPTERA.— An order of Insects, characterised by the posses

sion of a spiral proboscis, and of four large more or less scaly wings. It includes the well-known Butterflies and

Moths. LITTORAL.-Inhabiting the seashore. LOESS.—A marly deposit of recent (Post-Tertiary) date, which

occupies a great part of the valley of the Rhine.

MALACOSTRACA.—The higher division of the Crustacea, including

the ordinary Crabs, Lobsters, Shrimps, &c., together with the

Woodlice and Sand-hoppers. MAMMALIA.—The highest class of animals, including the ordinary

hairy quadrupeds, the Whales, and Man, and characterised by the production of living young which are nourished after birth by milk from the teats (Mammæ, Mammary glands) of the mother. A striking difference in embryonic development has led to the division of this class into two great groups; in one of these, when the embryo has attained a certain stage, a vascular connection, called the placenta, is formed between the embryo and the mother; in the other this is wanting, and the young are produced in a very incomplete state. The former, including the greater part of the class, are called Placental mammals; the latter, or Aplacental mammals, include the

Marsupials and Monotremes (Ornithorhynchus). MAMMIFEROUS. Having mammæ or teats (see MAMMALIA). MANDIBLES, in Insects. The first or uppermost pair of jaws, which

are generally solid, horny, biting organs. In Birds the term is applied to both jaws with their horny coverings. In Quadru

peds the mandible is properly the lower jaw. MARSUPIALS.-An order of Mammalia in which the young are born

in a very incomplete state of development, and carried by the mother, while sucking, in a ventral pouch (marsupium), such

as the Kangaroos, Opossums, &c. (see MAMMALIA). MAXILLÆ, in Insects. The second or lower pair of jaws, which are

composed of several joints and furnished with peculiar jointed appendages called palpi, or feelers.

MELANISM.—The opposite of albinism; an undue development of

colouring material in the skin and its appendages. METAMORPHIC Rocks.Sedimentary rocks which have undergone

alteration, generally by the action of heat, subsequently to

their deposition and consolidation. MOLLUSCA.–One of the great divisions of the Animal Kingdom,

including those animals which have a soft body, usually furnished with a shell, and in which the nervous ganglia, or centres, present no definite general arrangement. They are generally known under the denomination of “shell-fish;” the cattle-fish, and the common snails, whelks, oysters, mussels,

and cockles, may serve as examples of them. 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, &c.) 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, cither 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. ESOPHAGUS.—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 Cir

ripedes 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 Umbel

liferæ 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.
PAPILIONACE Æ.—An order of Plants (see LEGUMINOSÆ). The

flowers of these plants are called papilionaceous, or butterflylike, 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 ex

pense of, another organism. PARTHENOGENESIS.—The production of living organisms from un

impregnated eggs or seeds.

PEDUNCULATED.Supported upon a stem or stalk. The peduncu

lated 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 arc 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 super

ficial parts of animals. The cells secreting it are called pig

ment-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 Mam

MALIA.

PLANTIGRADES.—Quadrupeds which walk upon the whole sole of

the foot, like the Bears. Plastic.—Readily capable of change. PLEISTOCENE PERIOD.—The latest portion of the Tertiary epoch. PLUMULE (in plants).—The minute bud between the seed-leaves of

newly-germinated plants. PLUTONIC ROCKS.-Rocks supposed to have been produced by igne

ous action in the depths of the earth. POLLEN.—The male element in flowering plants; usually a fine

dust produced by the anthers, which, by contact with the stigma effects the fecundation of the seeds. This impregnation is brought about by means of tubes (pollen-tubes) which issue from the pollen-grains adhering to the stigma, and penetrate

through the tissues until they reach the ovary. POLYANDROUS (flowers).–Flowers having many stamens. POLYGAMOUS PLANTS.—Plants in which some flowers are rinisexual

and others hermaphrodite. The unisexual (male and female)

flowers, may be on the same or on different plants. POLYMORPHIC.—Presenting many forms. POLYZOARY.—The common structure formed by the cells of the

Polyzoa, such as the well-known Sea-mats.

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