The Origin of Species by Means of Natural Selection; Or, the Preservation of Favored Races in the Struggle for Life Volume 2

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 edition. Excerpt: ... glossary of the principal scientific terms used in the present volume. Aberrant.--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).--In 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. Abnormal.--Contrary to the general rule. Aborted.--An organ is said to be aborted, when its development has been arrested at a very early stage. Albinism.--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. Alg-e.--A class of plants including the ordinary sea-weeds and the filamentous fresh-water weeds. 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. 307 Alternation Op 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