26 



ESSAY ON CLASSIFICATION. 



Part I. 



SECTION VIII, 



THE GRADATION OF STRUCTURE AMONG ANIMALS. 



There is not only variety among animals and plants ; they differ also as to their 

 standing, their rank, their superiority or inferiority Avhen comj^ared to one another. 

 But this rank is difficult to determine ; for while, in some respects, all animals are 

 equally perfect, as they perform completely the pai't assigned to them in the general 

 economy of nature,^ in other respects there are such striking differences between 

 them, that their very agreement in certain features points at their superiority or 

 inferiority in regard to others. 



This being the case, the question first arises, Do all animals form one unbroken 

 series from the lowest to the highest? Before the animal kingdom had been studied 

 so closely as it has been of late, many able writers really believed that all animals 

 formed but one simple continuous series, the gradation of which Bonnet has been 

 particularly industrious in trying to ascertain.^ At a later j^eriod, Lamarck^ has 

 endeavored to show further, that in the complication of their structure, all the 

 classes of the animal kingdom represent only successive degrees, and he is so 

 thoroughly convinced that in his systematic arrangement classes constitute one grad- 

 ual series, that he actually calls the classes " degrees of organization." DeBlainville * 

 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 Eadiata, to converge again and unite in the Vertebrata. 

 But since it is now known how the great branches of the animal kingdom may be 

 circumscribed,^ notwithstandmg a few doubtful points j since it is now known how 



^ Ehrenbeug, (C. G.,) Das Naturreich ties Men- 

 schen, oder das Reich der willensfreien beseelten Na- 

 turkorper, in 29 Classen iibersichtlich geordnet, Ber- 

 lin, 1835, folio, (1 sheet). 



^ Bonnet, (Ch.,) Considerations sur les corps 

 organises, Amsterdam, 1762, 2 vols. 8vo. — Contem- 

 plations de la Nature, Amsterdam, 1704—05, 2 vols. 

 8vo. — Palingenesie philosophique, Geneve, 1769, 2 

 vols. 8vo. 



' Lamarck, (J. B. de,) Philosophic zoologique, 

 Paris, 1809, 2 vols. 8vo. 



* Blainville, (II. D. DE,) De I'Organisation des 

 Animaux, Paris, 1822, 1 vol. 8vo. 



^ Blumenbach. (J. Fr.,) Handbuch der verglei- 

 chenden Anatomie, Giittingen, 1824, 1 vol. 8vo. ; 

 Engl, by W. Lawrence, London, 1827, 1 vol. 8vo. 

 — CuviER, (G.,) Legons d' Anatomie comparee, ree. 

 et publ. par MM. Dumeril et Duvernoy, Paris, 

 1800-1805, 5 vols. 8vo. ; 2de edit., rev. par MM. 

 F. G. Cuvier et Laurillard, Paris, 1836-39, 10 vols. 

 8vo. — Cuvier, (G.,) Le Regne animal distribue 

 d'apres son organisation, Paris, 1817, 4 vols. 8vo. ' 



