PRINCIPAL SYSTEMS OF ZOOLOGY 225 



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 Sphygmozoa, those which have a heart or pulsating 

 vessels, and Asphycta, those in which the vessels do not pulsate. These 

 two sections are further subdivided: the first, into Articulata with 

 real articulations 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 investi- 

 gations, the very principle 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 contributed 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 perfection is 

 not what he means. He does not wish to convey the idea that all ani- 

 mals are equally perfect in their way, for he states distinctly that 

 "Infusoria have the same sum of systems of organs as Man," and the 

 whole of his system is intended to impress emphatically this view. 

 The separation of Man from the animals, not merely as a class but 

 as a still higher division, is especially maintained upon that ground. 

 The principle of classification adopted by Ehrenberg is purely 

 anatomical; the idea of type is entirely set aside, as is shown by the 

 respective position of his classes. The Myeloneura, it is true, corre- 

 spond to the branch of Vertebrata, and the Sphygmozoa to the Articu- 

 lata and Mollusca; but they are not brought together on the ground 

 of the typical plan of their structure, but because the first have a 

 spinal marrow and the other a heart or pulsating vessels with or with- 

 out articulations of the body. In the division of Tubulata it is still 

 more evident how the plan of their structure is disregarded, as that 

 section embraces Radiata (the Echinoidea and the Dimorphaea) Mol- 

 lusca (the Bryozoa), and Articulata (the Turbellaria, the Nematoidea, 

 and the Rotatoria), which are thus combined simply on the ground 



