12 GRAND DIVISIONS. 



ted to an' external crust or to a rigid covering* 

 They draw in their food through suckers or tubes 

 serving as mouths, in most cases. Air vessels, 

 through which respiration is performed, open on 

 the sides of their bodies or limbs. 



They have two eyes, which may be of two 

 kinds. The simple kind appears like a small 

 lens. The compound kind has its surface divi- 

 ded into an infinite number of lenses ; each an- 

 swering to a fibre of the optic nerves. Excepting 

 the classes of jointed worms and of spiders, all ar- 

 ticulated animals have antennae ; being jointed, fi- 

 liform, flexible horns. With these they seem to 

 effect many purposes ; such as examining bodies 

 within their reach, determining the state of the at- 

 mosphere, and to derive sensations of which we 

 have no knowledge. 



They have the sense of smell and of hearing ; 

 but it is not known in what organs these senses 

 are placed. Some have jaws of a curious char- 

 acter. Often a pair of strong pincers for grasp- 

 ing and breaking up their food, and for defence. 

 These are called mandibles. Two pairs within 

 these are called levers and lips. To the levers 

 or jaws are attached jointed filaments, called pal- 

 pi or feelers, which are supposed to serve the ani- 

 mal for examining its food. The tongue com- 

 monly adheres to the lower lever. In some the 

 fore feet serve in place of some of these appenda^ 

 ges ; in others the jaws are increased in number. 

 Some have a proboscis or tube through which food 

 is imbibed. 



They are mostly produced from eggs. Some 

 become perfect immediately from the egg ; but 

 more are changed from the egg to the larva, (cal- 

 led caterpillar, worm, maggot or skipper) from 



