28 CLASSIFICATION. 



Third Great Division. Animalia Articulata Articulated 



Animals. 



The interior skeleton replaced by an external one formed 

 of a skin more or less modified in its nature and consistence, 

 and composed of a series of rings, movable one upon another. 

 Nervous system consisting in two long cords extending through 

 the length of the abdomen, and dilated at certain distances into 

 knots or ganglions. The first of the knots placed above the 

 cesphagus, and called brain, communicates by threads, which 

 form a collar to the oesophagus, with those placed beneath the 

 abdomen; blood white except in the Annulata. There is a 

 rapid decline in the circulation from the first animals of this 

 division to the last, where we may say indeed that it does not 

 exist or is performed by simple imbibition. At least three 

 pairs of limbs when they exist at all. 



FIRST CLASS. ANNULATA. 



Blood red ; circulation complete ; body covered with a soft 

 skin, and divided into numerous rings ; respiration by bran- 

 chiae ; no articulated limbs ; no metamorphoses. 



SECOND CLASS, CRUSTACEA. 



Colourless blood contained in two kinds of vessels ; skin 

 encrusted with carbonate and phosphate of lime ; head con- 

 founded with the thorax ; four attennae or feelers ; two com- 

 pound eyes ; foot jaws ; always at least six articulated feet ; 

 respiration by branchiae ; no metamorphoses. 



THIRD CLASS. ARACHNIDES. 



Blood colourless ; two systems of vessels in those which 

 respire by lungs ; circulation as in insects in all which res- 

 pire by tracheae; head confounded with the thorax; eyes 

 simple ; more than three pairs of limbs ; no metamorphoses. 



FOURTH CLASS. INSECTS. 



Blood colourless ; distributing itself to the different parts 

 of the body by simple imbibition; body presenting three 

 parts head, thorax and abdomen ; generally three pairs of 

 limbs ; respiration by tracheae ; metamorphoses more or less 

 complete. 



