BARON CUVIER. 61 



fid animals : they all have red blood, a muscular heart, 

 a mouth with two jaws, one above, or before the other, 

 distinct organs for sight, hearing, smell, and taste, placed in 

 the cavities of the face, never more than four limbs, the 

 sexes always separated, and a similar distribution of medul- 

 lary masses, and of the principal branches of the nervous 

 system. When thoroughly examining each of the parts 

 of this great series of animals, we shall always find some 

 analogy between them all, even in the species the farthest 

 fi-om each other ; and we can follow the gradations of the one 

 same plan, from man to the last of the fishes. In the 

 second form there is no skeleton, the muscles are only at- 

 tached to the skin, which forms a soft envelope, contractile 

 in various senses, in many species of which are engendered 

 stony plates, called shells, the position and production of 

 which are analogous to those of the mucous body to which 

 they belong. Their nervous system and viscera are con- 

 tained in this general envelope ; the former is composed of 

 several scattered masses, united by nervous threads, the 

 principal of -which, placed on the oesophagus, bear the 

 name of brain. In general, they only possess the senses 

 of taste and sight, and even the last is often wanting. 

 Only one 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 organization 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, (fee. Their nervous system consists of two long 

 cords, which traverse the belly lengthwise, and are enlarg- 

 ed firom space to space into knots, or ganglions. The first 

 of these knots is situated above the oesophagus, and is con- 

 sidered as the brain ; but it is scarcely larger than those 

 which are in the belly, with which it communicates by 

 threads, which embrace the cBsophagus Hke a collar. The 

 envelope of this structure is divided by transversal folds into 



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