CLASSES. 39 
feet. They feed chiefly upon living animals. 
They do not pass through any material change 
after they are produced, as insects do. 
Examples. Spider, grey-beard. 
8. Insecta, animals with jointed limbs, and an- 
tena. They respire by two principal trachee or 
pipes running parallel to each other through the 
whole body ; which throw off at intervals many 
branches to the surface of the body, through which 
air 7s admitted. | 
The head and thorax are distinct, antenne two. 
They are mostly winged, having one or two pair; 
afew are without wings. ‘They have six feet, 
excepting that some of the wingless genera have 
more : their mouths consist of six pieces, dispos- 
ed in pairs, but do not all move in the same direction. 
One pair is sometimes called the mouth or mandi- 
bles, another the lips, another is a kind of cloven 
tongue. In some insects the mandibles become a 
kind of beak. Most insects pass through several 
states of transmigration. 1. The egg, 2. the lar- 
va, 3. the chirysails, 4. the perfect insect. 
Example. ‘thousand-leg, flea, grasshopper, 
butterfly, miller, house-ily. | 
MOLLUSCOUS ANIMALS 
ARE INCLUDED IN ONE* CLASS. 
9. Motuusca, bodies soft without internal skele- 
ton, external crust or jointed limbs. Covering, a 
soft skin without rings ; sometimes defended by 
stony plates. . 
Blood white or bluish. Their muscles being 
attached to the skin without any solid supporters ; 

* Cuvier divides them into six classes. But it appears to be more 
convenient to make orders of such obscure classes. 
