Page:Origin of Species 1872.djvu/453

 .—A minute animal: generally applied to those visible only by the microscope.

.—A class of worms in which the surface of the body exhibits a more or less distinct division into rings or segments, generally provided with appendages for locomotion and with gills. It includes the ordinary marine worms, the earthworms, and the leeches.

.—Jointed organs appended to the head in insects, Crustacea and centipedes, and not belonging to the mouth.

.—The summits of the stamens of flowers, in which the pollen or fertilising dust is produced.

or Aplacental Mammals.—See Mammalia.

.—Of or belonging to the Archetype, or ideal primitive form upon which all the beings of a group seem to be organised.

.—A great division of the animal kingdom characterised generally by having the surface of the body divided into rings called segments, a greater or less number of which are furnished with jointed legs (such as insects, crustaceans and centipedes).

.—Having the two sides unlike.

.—Arrested in development at a very early age.

.—The genus including the common acorn shells which live in abundance on the rocks of the sea-coast.

.—A class of animals allied to the reptiles, but undergoing a peculiar metamorphosis, in which the young animal is generally aquatic and breathes by gills. (Examples, frogs, toads, and newts.)

.—Large transported blocks of stone generally imbedded in clays or gravel.

.—A class of marine Mollusca, or softbodied animals, furnished with a bivalve shell, attached to submarine objects by a stalk which passes through an aperture in one of the valves, and furnished with fringed arms, by the action of which food is carried to the mouth.

.—Gills or organs for respiration in water.

.—Pertaining to gills or branchiæ.

.—A series of very ancient Palaeozoic rocks, between the Laurentian and the Silurian. Until recently these were regarded as the oldest fossiliferous rocks.

.—The dog-family, including the dog, wolf, fox, jackal, &c.

.—The shell enveloping the anterior part of the body in crustaceans generally; applied also to the hard shelly pieces of the cirripedes.

.—This term is applied to the great formation which includes among other rocks, the coal-measures. It belongs to the oldest, or Palæozoic, system of formations.

.—Of or belonging to the tail.

.—The highest class of the Molluscs or soft-bodied animals, characterised by having the mouth surrounded by a greater or less number of fleshy arms or tentacles, which, in most living species, are furnished with sucking-cups. (Examples, cuttle-fish, nautilus.)

.—An order of Mammalia, including the whales, dolphins, &c.,