OF THE ANNULOSA. 357 



some Hymenoptera ; from all which we may collect that 

 a natural group defies every rule founded on notions of 

 absolute division, and can only be preserved entire and 

 in its proper situation by its contents being referred to 

 some real or imaginary type, as the standard of compa- 

 rison to which these in a greater or less degree all ap- 

 proach. The tact of the naturalist is shown less by the 

 discovery of such a type than by his knowing when to dis- 

 trust it. For its accuracy he must rely upon its coin- 

 ciding with the general feeling of his fellow labourers in 

 the science, since, though every person may not be able to 

 detect an affinity, all ought to feel its truth when it has been 

 detected. But chiefly he must rely on its combining with 

 the other types to form one extensive plan and uniform 

 effect. 



The animals with whose history we are at present en- 

 gaged all undergo a distinct metamorphosis, by which the 

 wings are always developed, and often even the feet. As 

 the type of every Vertebrated animal is tetrapod, so these 

 insects seem all to be tetrapterous, or at least to aim at this 

 type of construction. Vestiges of wings are to be discovered 

 even in the flea, and their place in dipterous insects is 

 supplied by other organs. Wings however do not al- 

 ways exist, since each of the ten principal orders of in- 

 sects may afford instances of apterous species even after 

 the last metamorphosis. The correct mode of considering 

 insects, therefore, is as referable all to a type which is te- 

 trapterous. The Coleoptera indeed are not only some- 

 times totally apterous, but often have their upper wings 

 or elytra soldered together so as to form a case for the 

 body. Still I conceive the reader Avill now have little dif- 

 ficulty in comprehending my meaning, when I hereafter 



