The Origin of Species
by Charles Darwin
I am indebted to the kindness of Mr. W. S. Dallas for this
Glossary, which has been given because several readers have complained
to me that some of the terms used were unintelligible to them. Mr.
Dallas has endeavoured to give the explanations of the terms in as
popular a form as possible.
EDITOR'S NOTE: This
glossary did not appear in the first edition and has been reproduced
here directly from the sixth edition
- Forms or groups of animals or plants which deviate in important
characters from their nearest allies, so as not to be easily included
in the same group with them, are said to be aberrant.
ABERRATION (in Optics)
the refraction of light by a convex lens the rays passing through
different parts of the lens are brought to a focus at slightly
different distances, this is called spherical aberration; at
the same time the coloured rays are separated by the prismatic action
of the lens and likewise brought to a focus at different distances,
this is chromatic aberration.
- Contrary to the general rule.
- An organ is said to be aborted,
when its development has been arrested at a very early stage.
- Albinos are animals in which the
usual colouring matters characteristic of the species have not been
produced in the skin and its appendages. Albinism is the state of
being an albino.
- A class of plants including the
ordinary sea-weeds and the filamentous fresh-water weeds.
ALTERNATION OF GENERATIONS
- This term is applied to a peculiar mode of reproduction which
prevails among many of the lower animals, in which the egg produces a
living form quite different from its parent, but from which the
parent-form is reproduced by a process of budding, or by the division
of the substance of the first product of the egg.
- A group of fossil, spiral,
chambered shells, allied to the existing pearly Nautilus, but having
the partitions between the chambers waved in complicated patterns at
their junction with the outer wall of the shell.
- That resemblance of structures
which depends upon similarity of function, as in the wings of insects
and birds. Such structures are said to be analogous, and to be
analogues of each other.
- 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 summits of the stamens of
flowers, in which the pollen or fertilising dust is produced.
APLACENTALIA, APLACENTATA or Aplacental Mammals
- 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
- Having the two sides
- Arrested in development at a
very early stage.
- 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 gravels.
- A class of marine Mollusca,
or soft-bodied 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
- A Series of very
ancient Palæozoic rocks, between the Laurentian and the
Silurian. Until recently these were regarded as the oldest
- 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 or belonging to the tail.
- The highest class of the
Mollusca, 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., having the form of the body fish-like, the
skin naked, and only the fore-limbs developed.
- An order of Reptiles including
the Turtles, Tortoises, &c.
- An order of Crustaceans
including the Barnacles and Acorn-shells. Their young resemble those
of many other Crustaceans in form; but when mature they are always
attached to other objects, either directly or by means of a stalk, and
their bodies are enclosed by a calcareous shell composed of several
pieces, two of which can open to give issue to a bunch of curled,
jointed tentacles, which represent the limbs.
- The genus of Insects including the
Cochineal. In these the male is a minute, winged fly, and the female
generally a motionless, berry-like mass.
- A case usually of silky material, in
which insects are frequently enveloped during the second or
resting-stage (pupa) of their existence. The term `cocoon-stage' is
here used as equivalent to `pupa-stage.'
- A term applied to those
fruits of the Umbelliferæ which have the seed hollowed on the
- Beetles, an order of Insects,
having a biting mouth and the first pair of wings more or less horny,
forming sheaths for the second pair, and usually meeting in a straight
line down the middle of the back.
- A peculiar organ in the flowers of
Orchids, in which the stamens, style and stigma (or the reproductive
parts) are united.
- Plants in which the inflorescence consists
of numerous small flowers (florets) brought together into a dense
head, the base of which is enclosed by a common
envelope. (Examples, the Daisy, Dandelion, &c.)
- The filamentous weeds
of fresh water.
- A rock made up of
fragments of rock or pebbles, cemented together by some other
- The second envelope of a flower
usually composed of coloured, leaf-like organs (petals), which may be
united by their edges either in the basal part or throughout.
- The normal coincidence of
one phenomenon, character, &c., with another.
- A bunch of flowers in which those
springing from the lower part of the flower stalk are supported on
long stalks so as to be nearly on a level with the upper ones.
- The first or seed-leaves of
- A class of articulated
animals, having the skin of the body generally more or less hardened
by the deposition of calcareous matter, breathing by means of gills.
(Examples, Crab, Lobster, Shrimp, &c.)
- The old generic term for the
Beetles known as Weevils, characterised by their four-jointed feet,
and by the head being produced into a sort of beak, upon the sides of
which the antennæ are inserted.
- Of or belonging to the skin.
- The wearing down of land by
the action of the sea or of meteoric agencies.
- The wearing away of the
surface of the land by water.
DEVONIAN SYSTEM or
- A series of Palæozoic rocks, including the
Old Red Sandstone.
- A class of plants characterised by
having two seed-leaves, by the formation of new wood between the bark
and the old wood (exogenous growth) and by the reticulation of the
veins of the leaves. The parts of the flowers are generally in
multiples of five.
- The separation or
discrimination of parts or organs which in simpler forms of life are
more or less united.
- Having two distinct forms.
Dimorphism is the condition of the appearance of the same species
under two dissimilar forms.
- Having the organs of the sexes
upon distinct individuals.
- A peculiar form of Greenstone.
- Of or belonging to the back.
- A peculiar order of Quadrupeds,
characterised by the absence of at least the middle incisor (front)
teeth in both jaws. (Examples, the Sloths and Armadillos.)
- The hardened fore-wings of Beetles,
serving as sheaths for the membranous hind-wings, which constitute the
true organs of flight.
- The young animal undergoing
development within the egg or womb.
- The study of the development
of the embryo.
- Peculiar to a given locality.
- A division of the class
Crustacea, having all the segments of the body usually distinct, gills
attached to the feet or organs of the mouth, and the feet fringed with
fine hairs. They are generally of small size.
- The earliest of the three divisions
of the Tertiary epoch of geologists. Rocks of this age contain a
small proportion of shells identical with species now living.
allied to the May-fly.
- The totality of the animals naturally
inhabiting a certain country or region, or which have lived during a
given geological period.
- The Cat-family.
- Having become wild from a state of
cultivation or domestication.
- The totality of the plants growing
naturally in a country, or during a given geological period.
- Flowers imperfectly developed in
some respects, and collected into a dense spike or head, as in the
Grasses, the Dandelion, &c.
- Of or belonging to the foetus, or
embryo in course of development.
- A class of animals of
very low organisation, and generally of small size, having a
jelly-like body, from the Surface of which delicate filaments can be
given off and retracted for the prehension of external objects, and
having a calcareous or sandy shell, usually divided into chambers, and
perforated with small apertures.
- Containing fossils.
- Having a faculty of digging.
The Fossorial Hymenoptera are a group of Wasp-like Insects, which
burrow in sandy soil to make nests for their young.
- FRENA). A small band or fold
- FUNGUS). A class of
cellular plants, of which Mushrooms, Toadstools, and Moulds, are
- The forked bone formed by the union
of the collarbones in many birds, such as the common Fowl.
- An order of
Birds of which the common Fowl, Turkey, and Pheasant, are well-known
- The genus of birds which includes the
- A swelling or knot from which
nerves are given off as from a centre.
- Fishes covered with
peculiar enamelled bony scales. Most of them are extinct.
- A minute vesicle
in the eggs of animals, from which development of the embryo proceeds.
- A period of great
cold and of enormous extension of ice upon the surface of the earth.
It is believed that glacial periods have occurred repeatedly during
the geological history of the earth, but the term is generally applied
to the close of the Tertiary epoch, when nearly the whole of Europe
was subjected to an arctic climate.
- An organ which secretes or separates
some peculiar product from the blood or sap of animals or plants.
- The opening of the windpipe into
the oesophagus or gullet.
- A rock approaching granite in
composition, but more or less laminated, and really produced by the
alteration of a sedimentary deposit after its consolidation.
- The so-called Wading-birds
(Storks, Cranes, Snipes, &c.), which are generally furnished with
long legs, bare of feathers above the heel, and have no membranes
between the toes.
- A rock consisting essentially of
crystal of felspar and mica in a mass of quarts.
- The locality in which a plant or
animal naturally lives.
- An order or sub-order of
Insects, characterised by the possession of a jointed beak or rostrum,
and by having the fore-wings horny in the basal portion and membranous
at the extremity, where they cross each other. This group includes
the various species of Bugs.
- Possessing the organs
of both sexes.
- That relation between parts which
results from their development from corresponding embryonic parts,
either in different animals, as in the case of the arm of man, the
foreleg of a quadruped, and the wing of a bird; or in the same
individual, as in the case of the fore and hind legs in quadrupeds,
and the segments or rings and their appendages of which the body of a
worm, a centipede, &c., is composed. The latter is called
serial homology. The parts which stand in such a relation to
each other are said to be homologous, and one such part or
organ is called the homologue of the other. In different
plants the parts of the flower are homologous, and in general these
parts are regarded as homologous with leaves.
- An order or sub-order of
Insects having (like the Hemiptera) a jointed beak, but in which the
fore-wings are either wholly membranous or wholly leathery. The
Cicadoe, Frog-hoppers, and Aphides, are well-known
- The offspring of the union of two
- 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
- Excessively developed.
- A family of
Hymenopterous insects, the members of which lay their eggs in the
bodies or eggs of other insects.
- The perfect (generally winged)
reproductive state of an insect.
- The aboriginal animal or
vegetable inhabitants of a country or region.
- The mode of arrangement
of the flowers of plants.
- 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 particles
of their food to the orifice of the mouth.
- Feeding on Insects.
- Those animals which do not possess a
backbone or spinal column.
- Spaces left among the
tissues in some of the lower animals, and serving in place of vessels
for the circulation of the fluids of the body.
- Furnished with lamellæ
or little plates.
- LARVÆ). The first
condition of an insect at its issuing from the egg, when it is usually
in the form of a grub, caterpillar, or maggot.
- The upper part of the windpipe
opening into the gullet.
- 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.
- 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 stamens and
pistil are enclosed in a sheath formed by two other petals. The fruit
is a pod (or legume).
- 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.
- An order of Insects,
characterised by the possession of a spiral proboscis, and of four
large more or less scaly wings. It includes the well-known
Butterflies and Moths.
- Inhabiting the seashore.
- A marly deposit of recent
(Post-Tertiary) date, which occupies a great part of the valley of the
- The higher division of
the Crustacea, including the ordinary Crabs, Lobsters, Shrimps,
&c., together with the Woodlice and Sand-hoppers.
- 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 (Mammoe, 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
- Having mammæ; or
teats (See MAMMALIA).
MANDIBLES, in Insects
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
- 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
- The opposite of albinism; an
undue development of colouring material in the skin and its
rocks which have undergone alteration, generally by the action of
heat, subsequently to their deposition and consolidation.
- 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 cuttle-fish, and the
common snails, whelks, oysters, mussels, and cockles, may serve as
examples of them.
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.)
- The accumulations of fragments of
rock brought down by glaciers.
- The law of form or structure
independent of function.
- 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.
- Commencing development.
- Adapted for the purpose of
- 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.
- The arrangement of the veins or
nervures in the wings of Insects.
- 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.
semi-transparent 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, &c., from the surface of the eye.
- The simple eyes or stemmata of
Insects, usually situated on the crown of the head between the great
- The gullet.
- 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.
- A calcareous plate employed by
many Mollusca to close the aperture of their shell. The opercular
valves of Cirripedes are those which close the aperture of the
- The bony cavity for the reception of
- An organised being, whether plant
- A term applied to those
fruits of the Umbelliferæ which have the seed straight.
- Forms or groups apparently
intermediate between and connecting other groups are said to be
OVARIUM or OVARY (in
- 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.
OVULES (of plants)
- The seeds in
the earliest condition.
- A group of Mammalia, so
called from their thick skins, and including the Elephant, Rhinoceros,
- The oldest system
of fossiliferous rocks.
- Jointed appendages to some of the
organs of the mouth in Insects and Crustacea.
- An order of
Plants (see LEGUMINOSÆ). 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.
- An animal or plant living upon or
in, and at the expense of, another organism.
- The production of
living Organisms from unimpregnated eggs or seeds.
- Supported upon a stem or
stalk. The pedunculated oak has its acorns borne upon a footstalk.
PELORIA or PELORISM
appearance of regularity of structure in the flowers of plants which
normally bear irregular flowers.
- The bony arch to which the hind limbs
of Vertebrate animals are articulated.
- The leaves of the corolla, or second
circle of organs in a flower. They are usually of delicate texture and
- Having flattened,
leaf-like twigs or leafstalks instead of true leaves.
- The colouring material produced
generally in the superficial parts of animals. The cells secreting it
are called pigment-cells.
- Bearing leaflets on each side of a
- 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
PLACENTATA, or Placental Mammals
- See MAMMALIA.
- Quadrupeds which walk
upon the whole sole of the foot, like the Bears.
- Readily capable of change.
- The latest
portion of the Tertiary epoch.
PLUMULE (in plants)
- The minute
bud between the seed-leaves of newly-germinated plants.
- Rocks supposed to
have been produced by igneous action in the depths of the earth.
- 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.
having many stamens.
- Plants in which
some flowers are unisexual and others hermaphrodite. The unisexual
(male and female) flowers, may be on the same or on different plants.
- Presenting many forms.
- The common structure for the
Polyzoa, such as the well-known Sea-mats.
- Capable of grasping.
- Having a superiority of power.
- The feathers forming the tip of
the wing of a bird, and inserted upon that part which represents the
hand of man.
- Projecting portions of bones,
usually for the attachment of muscles, ligaments, &c.
- A resinous material collected by
the Hive-Bees from the opening buds of various trees.
- Exceedingly variable.
- 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
- 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
- The minute root of an embryo plant.
- One half of the lower jaw in the
Mammalia. The portion which rises to articulate with the skull is
called the ascending ramus.
- 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.
- 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.
- 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
- 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.
- 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.
- The Bramble Genus.
- Very imperfectly developed.
- 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.
- 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.
- The gelatinous material of which
the bodies of the lowest animals (Protozoa) are composed.
- The horny plates with
which the feet of birds are generally more or less covered, especially
deposited as sediments from water.
- The transverse rings of which the
body of an articulate animal or Annelid is composed.
- The leaves or segments of the calyx,
or outermost envelope of an ordinary flower. They are usually green,
but sometimes brightly coloured.
- Teeth like those of a saw.
- Not supported on a stem or
- A Very ancient
system of fossiliferous rocks belonging to the earlier part of the
- The setting apart of
a particular organ for the performance of a particular function.
- 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 various organs of the body.
- 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.
- The breast-bone.
- The apical portion of the pistil in
- Small leafy organs placed at the
base of the footstalks of the leaves in many plants.
- The middle portion of the perfect
pistil, which rises like a column from the ovary and supports the
stigma at its summit.
- Situated beneath the
- Adapted for sucking.
SUTURES (in the skull)
lines of junction of the bones of which the skull is composed.
- TARSI). The jointed feet of
articulate animals, such as Insects.
- 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
- The latest geological epoch,
immediately preceding the establishment of the present order of
- The windpipe or passage for the
admission of air to the lungs.
- Three-fingered, or composed
of three movable parts attached to a common base.
- 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.
- Presenting three distinct
- 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).
- Hoofed quadrupeds.
- Consisting of a single
- Containing blood-vessels
- Like a worm.
VERTEBRATA: or VERTEBRATE
- The highest division of the animal kingdom, so called
from the presence in most cases of a backbone composed of numerous
joints or vertebroe, which constitutes the centre of the
skeleton and at the same time supports and protects the central parts
of the nervous system.
- The circles or spiral lines in which
the parts of plants are arranged upon the axis of growth.
- See neuters.
- The earliest stage in the
development of many of the higher Crustacea, so called from the name
of Zoea applied to these young animals when they were supposed
to constitute a peculiar genus.
- 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.
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