The Origin of Species, Charles Darwin [trending books to read .TXT] 📗

ordinary crabs, lobsters, shrimps, etc., 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 (Mammae, 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 mammae 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 quadrupeds 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, etc. (see Mammalia).

Maxillae

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 “shellfish;” the cuttlefish, and the common snails, whelks, oysters, mussels, and cockles, may serve as examples of them.

Monocotyledons 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 freshwater 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 semitransparent 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.

Operculum

A calcareous plate employed by many Molluscae 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 Umbelliferae which have the seed straight.

Osculant

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

Ova

Eggs.

Ovarium 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, etc.

Palaeozoic

The oldest system of fossiliferous rocks.

Palpi

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

Papilionaceae

An order of plants (see Leguminosae). 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 footstool.

Peloria 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