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articulates but also to the vertebrates. The next two classes are accord- 

 ing to their shells. The last class consists of those constructed 

 internally on the plan of the mollusks, but externally resembling the 

 lower group. The radiate classes extend from the well known star 

 fishes to the simple celled infusoria. 



In deciding the scale of the natural series a certain method has 

 always presented itself, that is, to select a certain point as a standard, 

 compare the objects we wish to rank, and when compared, that which 

 most neai'ly approaches the standard has precedence. In selecting the 

 standaixl, that end of the scale is most naturally chosen which is the 

 perfection of all types. Thus, throughout the whole animal kingdom, 

 when we speak of a thing being highly or lowly developed, we refer ta 

 it as approaching near to or departing from the likeness of man in the 

 construction of its parts. 



Up to the time of Cuvier the idea was to form one continuous line 

 from the highest to the lowest form of animal life. Cuvier renounced 

 this plan, placing many of his sub-kingdoms and classes on almost equal 

 footing. He, however, failed to explain the discrepancies or elucidate 

 the plan of his series. This want of regularity has always perplexed 

 classifiers who have followed the Cuvierian, school. Macleay, a Scotch 

 naturalist, attempted to arrange all in groups represented by circles, 

 the series being continuous where the circles came in contact. The 

 whole diificulty is due to their observation not being based upon proper 

 theories. These systems have been formed on certain characters, with- 

 out first discovering why these characters were present or ascertaining 

 by what theory they could be explained. They failed to recognize the 

 import of their facts and continued their investigations in the wrong 

 direction. 



At the same time that Cuvier was constructing his animal 

 kingdom, and probably from the same influences that caused him to 

 look deeper than his predecessors, others also commenced to investigate 

 the subject, and although no system was evolved, the principles upon 

 which we mast build a system jturely natural were discovered. All 

 other systems were formed by studying the characteristics of the 

 natural groups, and then bringing together all to which they could be 

 applied. This method studies nature as a whole, from the most lowly 



