30 ESSAY ON CLASSIFICATION 



has endeavored to show further that in the complication of their 

 structure all the classes of the animal kingdom represent only suc- 

 cessive degrees, and he is so thoroughly convinced that in his sys- 

 tematic arrangement classes constitute one gradual series, that he 

 actually calls the classes "degrees of organization." De Blainville^^ 

 has in the main followed in the steps of Lamarck, though he does 

 not admit quite so simple a series, for he considers the Mollusks and 

 Articulates as two diverging branches ascending from the Radiata, 

 to converge again and unite in the Vertebrata. But now, since it is 

 known how the great branches of the animal kingdom may be cir- 

 cumscribed,^- notwithstanding a few doubtful points; since it is still 

 more accurately known how most classes should be characterized 

 and what is their respective standing; since every day brings dissent- 

 ing views respecting the details of classification nearer together, the 

 supposition that all animals constitute one continuous gradated 

 series can be shown to be contrary to nature. Yet the greatest diffi- 

 culty in this inquiry is to weigh rightly the respective standing of the 



*^ De V Organisation des animaux (Paris, 1822). 



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 Paris: G. Dum^ril et G. Duvernoy, 1800-1805; 2d ed., 10 vols., F. Cuvier, C. Laurillard, 

 et G. Duvernoy, 1836-1844); Le Regne animal ■ distribue d'apres son organisation (4 

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 douin, et al., 1836-1846; tr., Edward Griffith, et al., 16 vols., London, 1824-1833); 

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 Gottingen, 1802-1816), and Die Erscheinungen und Gesetze des organischen Lebens 

 (5 vols., Bremen, 1831-1837); Stefano delle Chiaje, Istituzioni d'Anatomia e Fisiologia 

 comparata (Naples, 1832); Carl G. Carus, Lehrbuch der vergleichenden Zootomie (2d 

 ed., 2 vols., Leipzig, 1834), Grundsdtze der vergleichenden Anatomie (Diesden, 1828), 

 translated by R. T. Gore as An Introduction to the Comparative Anatomy of Animals 

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