138 



ESSAY ON CLASSIFICATION. 



Part I. 



Why, then, should not observers of nature have appreciated rightly the relationship 

 between animals or plants befoi'e getting a scientific clue to the classifications they 

 were led to adopt as practical? 



Such considerations, above all others, have guided and encouraged me while I 

 was seeking fi3r the meaning of all these systems, so different one from the other in 

 their details, and yet so similar in some of their general features. The history 

 of our science shows how early some of the principles, which obtain to this day, 

 have been acknowledged by all reflecting naturalists. Aristotle, for instance, already 

 knew the principal differences which distinguish Vertebrata from all other animals, 

 and his distinction of Enaima and Aiimna^ corresponds exactly to that of Vertebrata 

 and Invertebrata of Lamarck,^ or to that of Flesh- and Gut-Animals of Oken,^ or to that 

 of M)jdoneura and Ganglioneura of Ehrenberg;^ and one who is at all familiar 

 with the progress of science at different periods can but smile at the claims to 

 novelty or originality so frequently brought forward for views long before current 

 among men. Here, for instance, is one and the same fact presented in difierent 

 aspects; first, by Aristotle with reference to the character of the formative fluid, 

 next by Lamarck Avith reference to the general frame, — for I will do Lamarck 

 the justice to believe, that he did not unite the Invertebrata simj^ly because they 

 have no skeleton, but because of that something, which even Professor Owen fiiils 

 to express,^ and which yet exists, the one cavity of the body in Invertebrata con- 

 taining all organs, whilst Vertebrata have one distinct cavity for the centres of the 

 nervous system, and another for the organs of the vegetative life. This acknowledg- 

 ment is due to Lamarck as truly as it would be due to Aristotle not to accuse 

 him of having denied the Invertebrata any fluid answering the office of the blood, 

 though he calls them Anaima ; for he knew nearly as well as we now know, 

 that there moves a nutritive fluid in their body, though that information is 

 generally denied him because he had no correct knowledge of the circulation of 

 the blood. 



Again, when Oken speaks of Flesh-Animals he does not mean that Vertebrates 

 consist of nothing but flesh, or that the Invertebrates have no muscular fibres ; 

 but he brings prominently before us the presence, in the former, of those masses, 

 forming mainly the bulk of the body, which consist of flesh and bones as well 

 as blood and nerves, and constitute another of the leading features distinguishing 

 Vertebrata and Invertebrata. Ehrenberg presents the same relations between the 

 same beings as expressed by their nervous system. If we now take the expressions 



' Histor. Anim., Lib. I., Ch. 5 .ind 6. 

 2 Anim. Vert, 2d edit., vol. 1, p. 313. 

 ^ Natui'pliilosophie, 3d edit., p. 100. 



* Das Naturreicli des Menschen ; a diagram, upon 

 a large sheet, folio. 



^ Comparat. Anat. of Liv., 2d edit., j). 11. 



