marks
of the rest. In the case of other _natural_ groups, the formation of the
larger groups, into which we collect the _infimae species_, is suggested
indeed by resemblance to types (since we form each such larger group
round a selected _kind_ which serves as its exemplar); but the group
itself, when formed, is determined by definite characters.

Class names should by the mode of their construction help those who have
learnt about the thing, to remember it, and those who have not learnt,
now to learn, by being merely told the name. This is best effected, in
the case of _kinds_, when the word indicates by its very formation the
properties it connotes. But this is seldom possible. For, though a
_kind_-name connotes not all the _kind_-properties, but some only which
serve as sure marks of the rest, even these have been found too many to
be included conveniently in a name (except in Elementary Chemistry,
where every compound substance has one distinctive index-property, viz.
the chemical composition). A subsidiary resource is to point out the
_kind's_ nearest natural affinities. For instance, in the binary
Nomenclature of Botany and of Zoology, the name of every species
consists of the name of the _natural_ group next above, with a word
added expressive of some quality in the nature or mode of discovery, or
what not, of the particular species itself. By this device (obtaining at
present only in Botany and Zoology), as well is the expression, in the
name, of many of the _kind's characters_ secured, as the use of names
economised, and the memory relieved. Except for some such plan, what
hope of naming the 60,000 known species of Plants?

CHAPTER VIII.

CLASSIFICATION BY SERIES.

The object of Classification generally is to bring our ideas of objects
into the order best fitted for prosecuting inductive enquiries into the
laws of the phenomena generally. But a Classification which aims at
facilitating an inductive enquiry into the laws of some special
phenomenon, must be based on that phenomenon itself. The requisites of
such a classification are, first, the bringing into one class all
_kinds_ of things which exhibit the phenomenon; next, the arranging
them in a _series_, according to the degrees in which they exhibit it.
Such a classification has been largely applied in Comparative Anatomy
and Physiology (and these alone), since there has been found a
recognisable difference in the degree in which animals possess