LINNAN SPECIES 7 
on civilized men paid closer attention to tne different 
kinds of plants, and the old herbalists discovered and 
described a number of different sorts of roses, of butter- 
cups, and of other plants, and distinguished each by a 
descriptive sentence. 
As more and more species came to be described, this 
method of designation became very cumbersome, until 
Linnzus, about the middle of the eighteenth century, 
adopted the idea of a binomial nomenclature (originally 
suggested by Bachmann), in which every species of 
each known genus received a separate name of its own 
to distinguish it, so that the different kinds of butter- 
cups were now known as Ranunculus acris, R. bulbosus, 
R. sceleraius, and so on. 
Linnzus himself appears to have had a very definite 
idea of what constituted a species, and in accordance 
with the view then current, he defined a species as 
being a group of organisms which owed its origin to a 
separate act of creation. From the nature of the case 
this definition could be of little use in practice. Prac- 
tically, then, species were defined as groups of animals 
or plants, the members of which resembled one another 
in definite morphological characteristics—that is to 
say, in constant features of form and structure. This 
definition has survived the downfall of the dogma of 
the constancy of species, and at the present day species 
as defined by Linnzus are found to be groups of much 
merit both for naturalness and for convenience—at 
any rate in the case of plants. The fact that inter- 
mediate forms and minor groups do sometimes and to 
some extent bridge over the gap which separates a 
