Cuvierian System of Zoology. 1 OS 



The germ, the embryo, the fcetus, the little new-born crea- 

 ture, are never perfectly of the same form as the adult, and 

 the difference is sometimes so great, that their assimilation 

 has obtained the name of a metamorphosis. No person could 

 foresee, without previous experience or information, that a 

 caterpillar would become a butterfly. 



All living beings are metamorphosed more or less in the 

 course of their growth ; that is, they lose certain parts, and 

 others are developed which were before inconsiderable. The 

 antennae, the wings, and all the parts of the butterfly were 

 before enclosed in the skin of the caterpillar ; this skin disap- 

 pears, with the jaws, the feet, and other organs which do not 

 remain with the butterfly. The feet of the frog are enclosed 

 in the skin of the tadpole, and the tadpole, to become a frog, 

 loses its tail, its mouth, and its gills. Even the infant, at its 

 birth, loses its placenta, and its surrounding membranes ; at a 

 certain age it acquires, by degrees, hair, teeth, and a beard ; 

 the relative size of the organs change, and its body enlarges 

 more in proportion than the head. 



The above selection of the most important facts in animal 

 physiology, will serve to indicate the influential characters, 

 which ought to serve as the bases for the first divisions of a 

 .zoological system. It is clear, says Cuvier, that these charac- 

 ters should be taken from the functions of sensation and 

 motion ; for these not only constitute the being an animal, but 

 they establish, in some manner, the degree of its animalisation 

 {jie son animalite). Observation confirms this inference, and 

 proves that the degree of developement and of complication of 

 the animal functions, is in concordance with that of the 

 organs of the vegetative functions. The heart, and the organs of 

 circulation, are a species of centre for the vegetative functions, 

 as the brain and trunk of the nervous system are for the animal 

 functions. We shall see that these two systems diminish {se 

 degrader) or disappear together. In animals of the lowest 

 class, where there are no visible nerves, there are no distinct 

 fibres, and the organs of digestion are simply excavated in the 

 homogeneousness of the body. The vascular system disap- 

 pears even before the nervous system in insects ; but, in gene- 

 ral, the dispersion of the medullary masses corresponds with 

 that of the muscular parts. 



The correspondence of the general forms, which result 

 from the arrangement of the motive organs, with the distribu- 

 tion of the nervous masses, and the energy of the circulating 

 system, ought therefore to serve as a basis for the first divi- 

 sions (coujpures) to be made in the animal kingdom. We 



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