322 ESSAY ON CLASSIFICATION. 



animals, which he divides into MYELONEURA, those with 

 nervous marrow (the Vertebrata,) and GTANGLIONEURA, 

 those with ganglia (the Invertebrata.) The Vertebrata 

 he subdivides into Nutrientia, those which take care of 

 their young, and Orphanozoa, those which take no care 

 of their young ; though this is not strictly true, as there 

 are many Fishes and Eeptiles which provide as carefully 

 for their young as some of the Birds and Mammalia, 

 though they do it in another way. The Invertebrata are 

 subdivided into Spliyymozoa, those which have a heart 

 or pulsating vessels, and Aspliycta., those in which the 

 vessels do not pulsate. These two sections are further 

 subdivided : the first, into Articulata with real articula- 

 tions, and rows of ganglia, and Mollusks without articula- 

 tion and with dispersed ganglia ; the second, into Tubulata 

 with a simple intestine, and Racemifera with a branching 

 intestine. These characters, which Ehrenberg assigns to 

 his leading divisions, imply necessarily the admission of 

 a gradation among animals. He thus negatives, in the 

 form in which he expresses the results of his investiga- 

 tions, the very principle which he intends to illustrate by 

 his diagram. The peculiar view of Ehrenberg, that all 

 animals are equal in the perfection of their organization, 

 might be justified, if it was qualified so as to imply a 

 relative perfection, adapted in all to the end of their 

 special mode of existence. As no one observer has con- 

 tributed more extensively than Ehrenberg to make known 

 the complicated structure of a host of living beings, which 

 before him were almost universally believed to consist of 

 a simple mass of homogeneous jelly, such a view would 

 naturally be expected of him. But this qualified per- 

 fection is not what he means. He does not wish to 

 convey the idea that all animals are equally perfect in 

 their way, for he states distinctly that " Infusoria have 



