What are species - E-book - Multi-format

What are Species? In its most general acceptation the word "species" signifies a kind or sort of something, which something is the genus to which the species belongs. Thus, a black stone is a species of the genus stone; a gray horse is a species of the genus horse; a scalene triangle is a species of the genus triangle; and, generally, it may be said that every adjective denotes a species of the genus indicated by the substantive to which it is applied.
In the technology of the physical sciences the term "species" has a more restricted signification. It is used to denote a group of individuals which corresponds with an early stage of that process of abstraction by which the qualities of individual objects are arranged in the subordinated categories of classification. The individual object alone exists in Nature; but, when individual objects are compared, it is found that many agree in all those characters which, for the particular purpose of the classifier, are regarded as important, while they differ only in those which are unimportant; and those which thus agree constitute a species, the definition of which is a statement of the common characters of the individuals which compose the species...