18 GENERAL CLASSIFICATION OF ANIMALS. 



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The invertebral animals are not capable of so satisfactory 

 and accurate an arrangement. Their structure is not yet suf- 

 ficiently understood ; but they may be divided into five 

 classes, according to such circumstances of resemblance as 

 the present state of knowledge with regard to them admits. 

 These classes are, 1. Insects. 2. Crustacea, as the lobster, 

 crab, and craw-fish. 3. Mollusca, as the oyster, the snail, 

 the cuttle-fish or squid, the clam, and the quahog. 4. Ver- 

 mes or worms, as the earthworm, the leech. 5. Zoophytes, 

 as the star-fish, the sea-urchin, the sea-anemone, the sun-fish, 

 the polypes, the sponges, and the animalcules. These classes 

 will all be more particularly described hereafter. 



The whole animal world then is arranged in two grand 

 divisions, and nine distinct classes, as in the following table : 



I. Vertebral Animals. 



3 alia5 Warm-blooded. 



II. Invertebral Animals. 



5. Insects. 



6. Crustacea, 



7. Mollusca. 



8. Vermes or Worms. 



9. Zoophytes. 



After these greater divisions into classes, there are several 

 smaller divisions, of which it will be useful to give some 

 account. 



CLASSES are subdivided into a greater or less number of 

 ORDERS ; and these are distinguished by some important, clear, 

 and remarkable peculiarities of conformation and structure, 

 which are common to all the animals included under each of 

 them. Thus, in the class Mammalia, the order Quadrumana 

 includes those animals which have hands upon all four of 

 their extremities, such as monkeys and apes ; the order Ru- 

 minantia, those which ruminate or chew the cud; the order 

 Carnivora, those adapted to feed principally on animal food 

 In the other classes, the divisions are of a similar kind. 



ORDERS are subdivided into GENERA. These comprehend 

 animals which have a general external resemblance to each 

 other, a kind of family likeness. Thus the genus Felis n- 

 cludes all those of the cat kind; and these animals, although 

 differing one from another very much in size and color, have 

 yet a close resemblance in their general form, figure, charac* 



