THE METAMORPHOSIS. 41 ~) 



ascends from its first simple beginnings to its highest perfection. 

 Nature attains these developments by antitheses. The immediate con- 

 sequence of such an antithesis, and which is visible in the homogeneous 

 mass of the body, is the antithesis between the interior and exterior, 

 whereby the internal cavity of the body which prepares the nutrimental 

 matter stands in opposition to its external surface, which con- 

 ditionates its form ; the further perfection of this first antithesis, 

 developes the various organs which stand in connexion with those two 

 organic systems. Thus from the originally simple digesting cavity of 

 the body, by degrees the intestinal canal and its various appendages 

 promoting digestion, viz. the glands, are formed ; and from the originally 

 uniform integument of the body, on the contrary, all those organs are 

 produced which promote and effect motion. The correctness of these 

 assertions is deduced from the history of the embryo forming in the 

 egg. Thus there appears in the several grades of development of the 

 animal kingdom, as it were a rivalry between the internal nutrimental 

 organs and the external organs of motion, and it therefore may be 

 readily imagined, in the varied direction Nature has pointed out for 

 its creatures to pursue, that in some animals the perfection of the 

 internal organs, and in others that of the external ones, has been 

 especially promoted. We call all those animals in which the first is 

 visible, namely, a prevailing development of the intestines, ventral 

 animals (Gastrozoa), but those in which the external organs attain 

 the greatest perfection, limb animals (Arihrozoa). 



But the highest perfection of the animal kingdom is by no means 

 attained by these two grades of development, for both as partial 

 developments must still appear unperfected. There only is the highest 

 perfection attained where the external as well as the internal organs 

 are equally perfected, and both have acquired their highest grade of 

 development. That this highest development appointed by nature for 

 the animal kingdom may be attained, there must be a third chief 

 group in the animal kingdom, the members of which make themselves 

 apparent by this homogeneous perfection of the external and internal 

 organs. We have long known this third group by the name of 

 vertebrate animals (Osteozoa or animalia vertebrata). 



The individuals of the animal kingdom which belong to these several 

 chief groups, it is easy to discover from the above character of each 

 group, and which the following Table exhibits : 



