108 THE VITAL FUNCTIONS. 



fasliioned, in a third, into instruments for taking up 

 the semi-fluid honey prepared by flowers ; while, 

 again, in a fourth, they are prolonged and folded 

 into a tubular proboscis, capable of suction, and 

 adapted to the drinking of fluid aliment. Pur- 

 suing the examination of these organs in another 

 series of articulated animals, we find them gradually 

 assuming the characters, as well as the uses of 

 instruments of prehension, of weapons for warfare, 

 of pillars for support, of levers for motion, or of 

 limbs for quick progression. Some of these re- 

 markable metamorphoses of organs have already 

 attracted our attention in a former part of this 

 treatise.* Jaws pass into feet, and feet into jaws, 

 through every intermediate form ; and the same 

 individual often exhibits several steps of these 

 transitions, and is sometimes provided also with 

 supernumerary organs of each description. In the 

 Arachnida, in particular, we frequently meet with 

 supernumerary jaws, together with various appen- 

 dices, which present remarkable analogies of form 

 with the antennae, and the legs and feet of the 

 Crustacea. 



The principal elementary parts which enter into 

 the composition of the mouth of an insect, when in 

 its most complete state of developement, are the 

 seven following : a pair of upper jaws, a pair of 

 lower jaws, an upper and a lower lip, and a tongue.f 

 These parts in the Locusta viridissima, or common 



♦ Vol. i. p. 259. 



t AH these parts, taken together, were termed by Fabricius, 

 instrumenta cibaria ; and upon their varieties of structure he 

 founded his celebrated system of entomological classification. 

 Kirby and Spence have denominated them trophi. See their Intro- 



