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199 SYSTEMATIC ARRANGEMENT OF INSECTS.

necessity for an accurate methodical classification by which living objects can be recognised and their relations to each other in some measure indicated, is even more strongly felt in regard to insects than any other department of the animal kingdom. This is occasioned by the great amount of their numbers, which much exceeds that of any other of the zoological classes. Most authors agree in affirming that not fewer than between 80,000 and 100,000 species are preserved in collections, and it is computed that the species existing in nature is not greatly short of 400,000. But the very circumstance which makes a well digested arrangement so desirable, likewise renders it of no easy attainment, owing to the difficulty of acquiring the requisite knowledge of such a multitude of objects. Their structural details are so endlessly diversified, their affinities and analogical relations so complex, and their modes of living, in many cases, of such difficult determination, that it is scarcely to be expected that a system will soon be constructed in which each shall find its appropriate position, a position at once forming a faithful index to all its most characteristic and essential properties. How far some