PROXIMATE GENUS.
The proximate genus is the next class above. To illustrate: “Animal” is a genus of “man,” but “biped” is the proximate genus of “man.” “Quadrilateral” is the genus of “square,” but “rectangle” is the proximate genus. The next class above “trigon” is polygon not figure. Hence “polygon” is the proximate genus of “trigon.”
GENUS AND SPECIES OF NATURAL HISTORY.
In natural history the following terms are used to denote the various grades of kinship in any scheme of classification: (1) kingdom, (2) class, (3) order, (4) family, (5) genus, (6) species, (7) variety, (8) the individual thing. Here “genus” and “species” are absolute not relative and occupy a fixed place in the scheme, while from a logical viewpoint any of the grades indicated between the lowest and highest would be the speciesof the next higher grade or a genus of the next lower; e. g., order is a species of “class,” while it is the genus of “family.”
GENUS, A DOUBLE MEANING.
We recall that any class name or genus has a double use, extensional and intensional. When considered from the standpoint of its extension, a genus represents a group of objects or is mathematical in its application, but when used in an intensional sense it represents a group of qualities or is logical in its application.
Considered extensionally the genus refers to a larger number of objects than the species. But when viewed intensionally the species refers to more qualities than the genus. This was made clear when discussing the law of variation in the extension and intension of terms.
(3) Differentia.
The differentia of a term is that attribute which distinguishes a given species from all the other species of the genus.
It has been observed that the species refers to more qualities than the genus. In fact, it represents all the attributes of the genus plus those which distinguish the particular species from the other species of the genus. These additional qualities are the differentiæ of the particular species.