« AnteriorContinuar »
PREHENSILE.-Capable of grasping.
and inserted upon that part which represents the hand of
PROCESSES.- Projecting portions of bones, usually for the attach
ment of muscles, ligaments, &c. PROPOLIS.— A resinous material collected by the Hive-Bees from
the opening buds of various trees. PROTEAN.–Exceedingly variable. Protozoa.— The lowest great division of the Animal Kingdom.
These animals are composed of a gelatinous material, and show scarcely any trace of distinct organs. The Infusoria, Foraminifera, and Sponges, with some other forms, belong to
this division. Pupa (pl. PUPÆ).—The second stage in the development of an
Insect, from which it emerges in the perfect (winged) reproductive form. In most insects the pupal stage is passed in perfect repose. The chrysalis is the pupal state of butterflies.
RADICLE.—The minute root of an embryo plant.
which rises to articulate with the skull is called the ascending
RANGE.— The extent of country over which a plant or animal is
naturally spread. Range in time expresses the distribution of a species or group through the fossiliferous beds of the earth's
crust. Retina.—The delicate inner coat of the eye, formed by nervous
filaments spreading from the optic nerve, and serving for the
perception of the impressions produced by light. RETROGRESSION.—Backward development. When an animal, as it
approaches maturity, becomes less perfectly organised than might be expected from its early stages and known relationships, it is said to undergo a retrograde development or meta
morphosis. RHIZOPODS.-A class of lowly organised animals (Protozoa), having
a gelatinous body, the surface of which can be protruded in the form of root-like processes or filaments, which serve for locomotion and the prehension of food. The most important order is that of the Foraminifera.
RODENTS.— The gnawing Mammalia, such as the Rats, Rabbits,
and Squirrels. They are especially characterised by the possession of a single pair of chisel-like cutting teeth in each jaw, between which and the grinding teeth there is a great
gap. RUBUS.—The Bramble Genus, RUDIMENTARY.–Very imperfectly developed. RUMINANTS.—The group of Quadrupeds which ruminate or chew
the cud, such as oxen, sheep, and deer. They have divided hoofs, and are destitute of front teeth in the upper jaw.
SACRAL.—Belonging to the sacrum, or the bone composed usually
of two or more united vertebræ to which the sides of the pelvis
in vertebrate animals are attached. SARCODE.—The gelatinous material of which the bodies of the
lowest animals (Protozoa) are composed. SCUTELLÆ.— The horny plates with which the feet of birds are gen
erally more or less covered, especially in front. SEDIMENTARY FORMATIONS.—Rocks deposited as sediments from
water. SEGMENTS.— The transverse rings of which the body of an articulate
animal or Annelid is composed. SEPALS.—The leaves or segments of the calyx, or outermost enve
lope of an ordinary flower. They are usually green, but some
times brightly coloured. SERRATURES.—Teeth like those of a saw. SESSILE.-Not supported on a stem or footstalk. SILURIAN SYSTEM.—A very ancient system of fossiliferous rocks
belonging to the earlier part of the Palæozoic series. SPECIALISATION.—The setting apart of a particular organ for the
performance of a particular function. SPINAL CHORD.—The central portion of the nervous system in the
Vertebrata, which descends from the brain through the arches of the vertebræ, and gives off nearly all the nerves to the va
rious organs of the body. STAMENS.—The male organs of flowering plants, standing in a circle
within the petals. They usually consist of a filament and an anther, the anther being the essential part in which the pollen,
or fecundating dust, is formed. STERNUM.—The breast-bone. STIGMA.—The apical portion of the pistil in flowering plants.
STIPULES.—Small leafy organs placed at the base of the footstalks
of the leaves in many plants. STYLE.—The middle portion of the perfect pistil, which rises like
a column from the ovary and supports the stigma at its
summit. SUBCUTANEOUS.—Situated beneath the skin. SUCTORIAL.-Adapted for sucking. SUTURES (in the skull).—The lines of junction of the bones of which
the skull is composed.
Tarsus (pl. TARSI).—The jointed feet of articulate animals, such
as Insects. TELEOSTEAN FISHES.--Fishes of the kind familiar to us in the
present day, having the skeleton usually completely ossified
and the scales horny. TENTACULA or TENTACLES.—Delicate fleshy organs of prehension
or touch possessed by many of the lower animals. TERTIARY.-The latest geological epoch, immediately preceding
the establishment of the present order of things. TRACHEA.—The windpipe or passage for the admission of air to
the lungs. TRIDACTYLE.—Three-fingered, or composed of three movable parts
attached to a common base. TRILOBITES.—A peculiar group of extinct Crustaceans, somewhat
resembling the Woodlice in external form, and, like some of them, capable of rolling themselves up into a ball. Their remains are found only in the Palæozoic rocks, and most
abundantly in those of Silurian age. TRIMORPHIC.-Presenting three distinct forms.
UMBELLIFERÆ.—An order of plants in which the flowers, which
contain five stamens and a pistil with two styles, are supported upon footstalks which spring from the top of the flower stem and spread out like the wires of an umbrella, so as to bring all the flowers in the same head (umbel) nearly to the same level.
(Examples, Parsley and Carrot). UNGULATA.—Hoofed quadrupeds. UNICELLULAR.—Consisting of a single cell.
VERTEBRATA: or VERTEBRATE ANIMALS.— The highest division of
the animal kingdom, so called from the presence in most cases of a backbone composed of numerous joints or vertebræ, which constitutes the centre of the skeleton and at the same time supports and protects the central parts of the nervous system.
WHORlS.—The circles or spiral lines in which the parts of plants
are arranged upon the axis of growth. WORKERS.-See neuters.
ZOËA-STAGE.—The earliest stage in the development of many
of the higher Crustacea, so called from the name of Zoëa applied to these young animals when they were supposed to constitute
a peculiar genus. Zooids.-In many of the lower animals (such as the Corals, Medusæ,
&c.) reproduction takes place in two ways, namely, by means of eggs and by a process of budding with or without separation from the parent of the product of the latter, which is often very different from that of the egg. The individuality of the species is represented by the whole of the form produced between two sexual reproductions; and these forms, which are apparently individual animals, have been called zooids.
Antarctic islands, ancient flora of,
Antechinus, ii. 219.
Ants attending aphides, i. 323.
slave-making instinct, i. 336.
neuters, structure of, i. 359.
of organic beings, ii. 225. lectual powers, i. 282.
on groups of species suddenly Aphis, developinent of, ii. 245.
Apteryx, i. 218.
Archeopteryx, ii. 80.
Artichoke, Jerusalem, i. 176.
Asclepias, pollen of, i. 236.
Asses, striped, i. 198.
improved by selection, i. 48.
Ateuchus, i. 168.
Aucapitaine, on land-shells, ii. 187.
Australia, animals of, i. 140.
dogs of, i. 328.
extinct animals of, ii. 121.
glaciers of, ii. 159.
Azara, on flies destroying cattle, i.
Azores, flora of, ii. 149.
Babington, Mr., on British plants,
Baer, Von, standard of Highness, i.
comparison of bee and fish, ii.
embryonic similarity of the
Vertebrata, ii. 241.
Balancement of growth, i. 182.