The Origin of Species

The Origin of Species Glossary


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.


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.


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.


Arrested in development at a very early stage.


The normal coincidence of one phenomenon, character, etc with another


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, etc.)


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.


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.


The young animal undergoing development within the egg or womb.


The totality of the animals naturally inhabiting a certain country or region, or which have lived during a given geological period.


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.


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.


Set of related species


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.


a black-breasted auk (seabird) with a narrow pointed bill, typically nesting on cliff ledges.


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.


The offspring of the union of two distinct species.


Excessively developed.


The aboriginal animal or vegetable inhabitants of a country or region.


Inhabiting the seashore.


That population increases more than the means of increasing subsistence does, so that in time, if no check is put upon the increase of population, many must starve or all be ill-fed. Applied to individual nations, like Britain, it intimated that something must be done to check the increase of population, as all the land would not suffice to feed its inhabitants.


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 (Ornithorhynchus).


Adapted for the purpose of swimming.


One who studies birds.

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.


1. small plant part developing into seed

2. immature egg


Readily capable of change.


Presenting many forms.


Having a superiority of power.


Exceedingly variable.


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 metamorphosis.


Very imperfectly developed.


The setting apart of a particular organ for the performance of a particular function.


Presenting three distinct forms.


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.