360 NATURAL ARKANGEMENT OF INSECTS. 



may be as well to examine the validity of the grounds 

 upon which the moderns have ventured to break up the 

 Aptera of Aristotle, and thus to render their definition 

 of an " insect " perfectly unintelligible to the world at 

 large. We will first endeavour to meet their arguments 

 upon general principles, and then to oppose them upon 

 other grounds. The French naturalists, Cuvier and 

 Latreille, upon discovering that the Crustacea breathed 

 by branchiae, at once separated them from insects, pro- 

 perly so called ; thereby assuming, that the mode by 

 which an animal breathes was, among the Anmtlo.sa, the 

 primary character to be looked to, and upon which we 

 were to decide what was, or was not, an insect. Now, 

 it is against this assumption, which is the very root of 

 all the modern changes introduced in the arrangement 

 of the annulose circle, that we take our stand. We 

 deny it is either logical in itself, or borne out by facts. 

 It is illogical, because it sets aside all the most pro- 

 minent distinctions by which insects are characterised 

 from other classes ; and makes that a primary principle 

 of separation, which does not even enter into the de- 

 finition of an annulose animal. If it be true, that the 

 Annulosa are characterised by their body and limbs 

 being articulated, by being provided with distinct feet, 

 and by undergoing a metamorphosis ; which, in the pre- 

 eminent types, gives to the adult insect the powers of 

 flight ; how, let us ask, can their mode of respiration be 

 placed higher than all these ? How can it be brought 

 in for the construction of primary divisions, when it 

 forms no part of the primary characters of the Annu- 

 losa ? The natural divisions of a group, such as this, 

 are indicated by the modifications of those characters 

 which are applicable to the whole ; and this we see is 

 actually the case, not merely with regard to insects, but 

 to all classes of animals. Thus, in the Ptilota. they are 

 all developed ; in the Aptera, the metamorphosis is im- 

 perfect, and the wings disappear ; in the Cirrliipedes, 

 there are no true legs, as in the former ; and finally, 

 there remains, in the Vermes and the Annelides, only 



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