in Natural History. 487 



systems and methods. 'I'lie naturalist has attempted only to 

 cany this necessary operation of the mind somewhat further 

 and with more precision, and has thus exposed himself to eirors, 

 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 or a 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 Linna?us, and continues to be the opinion 

 of some of his disciples, that genera are actually founded in na- 

 ture as much as species. " Naturœ opus semper est species et 

 genus." Phil. Bot. § 162. " Genus omne est naturale, in pri- 

 mordio tale creatum, hinc pro lubitu et secundimi cujuscunque 

 theoriam non proterve discindendum aut conglutinandum." 

 lb. § lo9- So the excellent and elegant author of the " Intro- 

 duction to Physiological and Systematic Botany," says, " A 

 genus comprehends one or more species so essentially different 

 in formation, nature, and often many adventitious qualities from 

 other plants, as to constitute a distinct family or kind no less 

 permanent, 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 

 VOL. XV. 3 R distinct 



