202 CLASSIFICATION OF INSECTS. 



like the organic, is double : of the immaterial we all are 

 ignorant. The animal kingdom is distributed under four 

 great divisions, distinguished from each other by organiza- 

 tion. One of these is a single group, the other three are 

 each double groups ; that is, they each contain two groups, 

 both of which possess the essential characters of the divi- 

 sion, but which, nevertheless, widely differ in some subor- 

 dinate character. These divisions, whether considered as 

 four or seven, may be termed provinces ; they are these : 



Vertebrated animals or Vertebrata. In this division, 

 which is that of man and of the animals most resembling 

 him, the brain and principal trunk of the nervous system 

 are enclosed in a bony envelope formed by the cranium 

 and vertebra; to the sides of this interniedial column are 

 attached the ribs and bones of the limbs, which form the 

 frame-work of the body ; the muscles generally cover the 

 bones, whose motion they occasion : this is a single group. 



Molluscous animals oiMolluscata. In this division there 

 is no skeleton ; the muscles are merely attached to the skin, 

 which constitutes a soft contractile envelope, in which, in 

 many species, are formed stony plates, called shells. The 

 nervous system is contained within this general envelope, 

 and is composed of several scattered masses connected by 

 nervous filaments : this is a double group. 



Annulated animals or Annulata. In this division the 

 nervous system consists of long cords, running longitudi- 

 nally throughout the body, and dilated at intervals into 

 knots or ganglions. The covering or envelope of the body 

 is divided by transverse folds into a certain number of rings, 

 whose teguments are sometimes hard, sometimes soft ; the 

 muscles are situated internally : this is a double group. 



Radiated animals or Radiata. The organs of sensation 

 and motion, in the preceding divisions, are symmetrically 

 arranged on the two sides of an axis ; in this division, 



