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to accept ttem as ttey are, we must needs repudiate 

 tliem altogether : under whicli circumstances, our diffi- 

 culties, botli in determination and nomenclature, would 

 be increased tenfold. We should also recollect, that 

 clusters which seem abruptly chalked out whilst our 

 knowledge is imperfect, are very frequently united with 

 others when fresh discoveries are made, and the inter- 

 mediate grades brought to light : so that their apparent 

 isolation may oftentimes arise from our ignorance of the 

 absent links, rather than from the fact itself. It would 

 surely be more desirable, therefore, when viewed even 

 in the light of expediency alone, to submit to the possi- 

 bUity of a few neutral species being conceded, with equal 

 reason, to different groups, than to amalgamate the 

 whole, and so lose sight of the general method or 

 arrangement, into which the various creatures do un- 

 questionably (in a broad sense) dispose themselves. If, 

 however, there be any truth in the generic doctrine 

 as above enunciated, the question of convenience may be 

 omitted from our speculations in toto, — seeing that all 

 genera (except those whose present abruptness is the 

 effect of accident) fuse into others with which they are 

 in immediate contact : so that in reality, unless we 

 ignore these natural assemblages from first to last, we 

 have no choice left us as regards the equivocal forms ; 

 but must consent to recognize them as of doubtful loca- 

 tion, and as possessing an equal right to be placed in 

 one or the other of two consecutive groups, — according 



