342 PRACTICAL AND SCIENTIFIC ZOOLOGY. 



sufficiently marked to render them recognisable. Whe- 

 ther we term these parts of the great system of nature, 

 circles, divisions, or groups, is immaterial, the three 

 words, in fact, to prevent tautology, will be here consi- 

 dered synonymous : the reader, however, must under- 

 stand that they designate, each and all, an assemblage of 

 objects, whose affinities, more or less, are circular. 



(422.) It is obvious that, in proportion to the pre- 

 cision which we can attain in the determination of a 

 group, so do we also give stability to all that belongs to 

 it. So soon as a group, therefore, has been verified by 

 the tests enumerated in the last chapter, it becomes, in 

 the truest sense of the word, definite: it therefore follows, 

 if we can ascertain what is the relative rank or value of 

 such a group, in reference to other definite groups, we 

 can then give a definite meaning to the name we bestow 

 upon it. If, in short, groups are definite, the names 

 indicative of their rank must be definite also, provided 

 a uniformity in their nomenclature is preserved. Authors, 

 indeed, are accustomed to distinguish their artificial 

 groups by many of the same terms (as order, tribe, 

 family, &c.) which we are about to explain ; but the 

 student must remember that, unless otherwise stated 

 these terms, which he will meet with in other systems, 

 are merely conventional ; being founded, not upon any 

 fixed plan of proceeding, but upon the mere opinion of 

 the author. It is to Mr. MacLeay and to his dis- 

 ciples that our science is indebted for the introduction 

 of this definite system of naming groups, the least ad- 

 vantage of which is, that, when we now talk of a natural 

 family, or a natural order*, we immediately know the 

 determinate value of the group spoken of. We shall 

 devote this chapter to the explanation and illustration of 

 those groups whose rank or value have been ascertained; 

 and conclude with a few remarks upon species and 

 their varieties. The different ranks of divisions or 



* I regret to observe, however, that very recently some of our entomolo. 

 gists call their divisions by these names, without bringing forward any evi. 

 dence or proof whatever that they are " natural," 



