72 UNITY OF SYSTEM. 



ON UNITY OF SYSTEM. 



( Continued from page 00.) 



The system or classification of animals is wholly in unison with their 

 chronological distribution, or with their creation in successive geological 

 epochs, and accordingly affords innumerable illustrations of the law of 

 degradation, which is manifest in all the successive subdivisions of the 

 animal kingdom. It is apparent in every species by the comparison of 

 the early state with the final state, and of one part of the structure 

 with another part. All kinds of living creatures are alike in their first 

 origin, and in the progress of growth the characters which are common 

 to the whole animal kingdom first appear, and then the distinctive 

 character of the class, the order, the family, the genus, and the species 

 are successively evolved, until all the characters have their most full 

 development, and the creature has attained its most perfect state. The 

 relation of classes and of successive lesser groups with each other is most 

 apparent in the more simple forms of each group; and the more the 

 character of a species, of a genus, or of a class is developed, the less is 

 its affinity with any other species, genera, or classes. So the Radiata, 

 Mollusca, Articulata, and Vertebrata are most allied to each other in 

 their lower forms and in their earlier growth, and, as it were, in pro- 

 portion as they are degraded or more or less deprived of their peculiar 

 characters. So also a species is degraded in proportion as it wants its 

 distinction from other species; the degradation of a genus is caused by 

 the total or partial cessation of its most characteristic species; the family 

 has the same relation to the genus, and the order to the family. 



The primary divisions of animals and the divisions and subdivisions of 

 each of them are not linked together by the highest form of the inferior 

 division being connected with the superior division, but quite otherwise; 

 that is, they are united by the lowest forms, and more especially by the 

 earlier state of the lower forms, when comparatively all the characters are 

 in common. Thus, in proportion as a creature is more highly organized, 

 or develops more of the characteristics of its class, it becomes more remote 

 from the classes that are higher, as well as those that are lower than its 

 own. 



The system or classification of animals is therefore in accordance with 

 their chronological succession and geographical distribution, and equally 

 subject to the law of degradation, which also governs their growth and 

 their comparative structure. 



It is well known that the higher classes in their progressive growth pass 

 through states or transition forms which resemble or are akin to the per- 

 manent or final states of the inferior classes. But, by way of compensation, 



