BARON CUVIER. 109 



family can boast of the organ of hearing ; they 

 have always a complete system of circulation, 

 and organs peculiarly adapted to respiration ; 

 those of digestion and secretion are nearly as 

 complicated as the same organs in vertebrated 

 animals. This second form is called that of 

 molluscous animals ; and although the general 

 plan of their organisation is not as uniform, 

 with regard to their external appearance, as that 

 of vertebrated animals, there is still a greater or 

 lesser degree of resemblance in the structure 

 and functions of these parts. 



*' The third form is that which is to be found 

 in insects, worms, &c. Their nervous system 

 consists of two long cords, which traverse the 

 belly lengthwise, and are enlarged from space to 

 space into knots, or ganglions. The first of 

 these knots is situated above the oesophagus, and 

 is considered as the brain ; but it is scarcely 

 larger than those which are in the belly, with 

 which it communicates by threads, which em- 

 brace the oesophagus like a collar. The envelope 

 of this structure is divided by transversal folds 

 into a certain number of rings, the teguments of 

 which are sometimes hard, and at others soft, 

 but to the interior of which the muscles are 

 always attached. The trunk often bears ar- 



