226 ESSAY ON CLASSIFICATION 



that they have vessels which do not pulsate and that their intestine 

 is a simple sac or tube. The Racemifera contain also animals con- 

 structed upon different plans, united on account of the peculiar struc- 

 ture of the intestine, which is either forked or radiating, dendritic 

 or racemose. 



The limitation of many of the classes proposed by Ehrenberg is 

 quite objectionable when tested by the principles discussed above. 

 A large proportion of them are indeed founded upon ordinal char- 

 acters only, and not upon class characters. This is particularly evi- 

 dent with the Rotatoria, the Somatotoma, the Turbellaria, the Ne- 

 matoidea, the Trematodea, and the Complanata, all of which belong 

 to the branch of Articulata. The Tunicata, the Aggregata, the Bra- 

 chiopoda, and the Bryozoa are also only orders of the class Acephala. 

 Before Echinoderms had been so extensively studied as of late, the 

 separation of the Echinoidea from Asteroidea might have seemed 

 justifiable; at the present day it is totally inadmissible. Even Leuckart, 

 who considers the Echinoderms as a distinct branch of the animal 

 kingdom, insists upon the necessity of uniting them as a natural 

 group. As to the Dimorphasa, they constitute a natural order of the 

 class Acalephae, which is generally known by the name of Hydroids. 



CLASSIFICATION OF BtJRMEISTER 



The following diagram is compiled from the author's Geschichte der Schopfung 

 (Leipzig, 1843). 



Type I. Irregular Animals. 

 1st Subtype. Cl. 1. Infusoria. 



Type II. Regular Animals. 

 2d Subtype. Cl. 2. Polypina. Ord. Bryozoa, Anthozoa. 

 3d Subtype. Cl. 3. Radiata. Ord. Acalephae, Echinodermata, Scytodermata. 



Type III. Symmetrical Animals. 

 4th Subtype. Cl. 4. Mollusca. Ord. Perig)'mna (Tunicata); Cormopoda (Acephala); 

 Brachiopoda, Cephalophora (Pteropoda and Gasteropoda); Cephalo- 

 poda. 

 5th Subtype. Arthrozoa. 



Cl. 5. Vermes. Ord. Helminthes, Trematodes, and Annulati. 



Cl. 6. Crustacea. 1°. Ostracoderma. Ord. Prothesmia (Cirripedia, Siphonostoma, 

 and Rotatoria); Aspidostraca (Entomostraca: Lophyropoda, Phyllopoda, Pacilo- 

 poda, Trilobitae.) 2°. Malacostraca. Ord. Thoracostraca (Podophthalma); and 

 Arthrostraca (Edriophthalma.) 

 Cl. 7. Arachnoda. Ord. Myriapoda, Arachnidae. 



Cl. 8. Insecta. Ord. Rhynchota, Synistata, Antliata, Piezata, Glossata, Eleuth- 

 erata. 

 6th Subtype. Osteozoa. (Vertebrata.) 



