in Natural History. 487 
systems and methods. The naturalist has attempted only to 
carry this necessary operation of the mind somewhat further 
and with more precision, and has thus exposed himself to errors, 
which the vulgar have escaped. "Thus, although there are but 
two modes of reasoning; namely, by the use of words expressive 
of an individual and its attributes, or by general words indica- 
tive of an aggregation of individuals with their common attri- 
butes; yet naturalists have used their terms in a different sense, 
and have invented additional ones, such as order, tribe, cohort, 
family, class, by which they attempt to express with more accuracy 
larger generalizations than they would do by employing a ge- 
neric term, and as if they could settle the relative rank of the 
different groups whose existence they have assumed. Whereas 
the truth is, that in many instances a class may be equivalent to 
an order ora genus. ‘These different gradations, thus strictly 
aimed at, are gratuitous assumptions with which Nature has 
nothing to do; and which frequently lead to the establishment 
of false hypotheses. ; | 
‘It was the opinion of Linnæus, and continues to be the opinion 
of some of his disciples, that genera are actually founded in na- 
ture as much as species. ‘‘ Nature opus semper est species et 
genus." Phil. Bot. § 162. ** Genus omne est naturale, in pri- 
mordio tale creatum, hinc pro lubitu et secundum cujuscunque 
theoriam non proterve discindendum aut conglutinandum." 
1b. § 159. So the excellent and elegant author of the “< Intro- 
duction to Physiological and Systematic Botany," says, “A 
s comprehends one or more species so essentially different 
n many adventitious qualities from 
distinct family or kind no less 
ermanent, and founded in the immutable laws of the creation, 
than the different species of such a genus. "Thus in the animal 
kingdom a horse, ass, and zebra, form three species of a very 
3 R distinct 
genu 
in formation, nature, and ofte 
. other plants, as to constitute a 
VOL. XV. 
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