INSECTA. 345 



were of the feeblest and simplest character, a rowing of the body 

 through an element of equal density with itself, or a trailing of the 

 body along the ground, which supported it at every point. As we 

 advanced to the survey of the Articulate series of animals, we saw 

 the integument progressively hardened ; divided into segments which 

 were united by flexible joints ; at length supported upon moveable 

 jointed limbs, consisting of hollow columns of integument compacted 

 into a dense exterior crust, capable of serving the office of levers and 

 fulcra, whereby the animal could raise its belly from the dust, and 

 swiftly traverse the surface of the ground. 



We now come to a class of Articulata in which the highest problem 

 of animal mechanics is solved, and the entire body and its appendages 

 can be lifted from the ground and be propelled through the air. The 

 species which enjoy this swiftest mode of traversing space breathe 

 the air directly : but their organs of respiration are peculiarly modi- 

 fied in relation to their powers of locomotion ; they consist of innu- 

 merable tracheee commencing from lateral pores called stigmata, or 

 by anal tubes, which are ramified through and over every tissue and 

 organ of the body. The nervous system is homogangliate ; the organs 

 of sense include two jointed antennse and two compound eyes ; the 

 skeleton is principally external, and cut deeply into segments, whence 

 the name of the class Insecta. 



Not every Insect, however, has the power of flight, nor any Insect 

 save in its last and most perfect state ; many undergo most remark- 

 able transformations before they acquire their wings, and although 

 some Insects, which ultimately are so endowed, undergo a less amount 

 of change, yet the metamorphoses are always least remarkable in the 

 apterous species. 



Of these lowest members of the class of Insects^ many have more 

 than three pairs of legs, have sometimes indeed eighty pairs and 

 upwards in their mature state : metamorphic development exhausts 

 itself, as in the Anellides, in the successive acquisition of new seg' 

 ments * and legs in addition to those which previously or originally 

 existed ; these Insects are therefore termed Myriapoda. 



True orHexapod Insects have thirteen rings ; one for the head, three 

 for the thorax, and nine for the abdomen. Certain flying Insects 

 in their early or larval state present several pairs of rudimental feet, 

 in addition to those attached to the first three segments succeedino- 

 the head ; but no true Insect in its mature state has more than the 

 three pairs of articulated limbs just indicated. 



* Always, as De Geer, Savi, and Newport have shown, developed between the 

 penultimate and anal segments. 



