42 GRAND DIVISIONS. 
ted to an external crust or to a rigid covering. 
‘They draw in their food threugh 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 
Jens. 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 antenne ; 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 itis 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- 
ang 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-_ 
pior 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- 
Jed caterpillar, worm, maggot or skipper) from 
