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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).
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.
Crustacea, especially belonging to the lower groups. In this
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,
PALÆOzoic.—The oldest system of fossiliferous rocks.
Insects and Crustacea.
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
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.