Chap. III. 



ANATOMICAL SYSTEMS. 



205 



Tlie classification with which Owen ' introduces his " Lectures on Comparative 

 Anatomy" is very instructive, as showing, more distinctly than other modern systems, 

 the unfortunate ascendency which the consideration of the complication of structure 

 has gained of late over the idea of plan. His provinces, it is true, correspond 

 in the main to the branches of Cuvier, with this marked difference, however, that 

 he does not recognize a distinct province of Radiata coequal with those of Mollusca, 

 Articulata, and Vertebrata, but only admits Radiaria as a subprovince on a level 

 with Entozoa and Infusoria. Here, the idea of simplicity of structure evidently 

 prevails over that of plan, as the subprovinces Radiaria, Entozoa, and Infusoria 

 embrace, besides true Radiata, the lowest types of two other branches, Mollusks 

 and Articulates. On the other hand, his three subprovinces correspond to the 

 first three types of von Siebold ; the Infusoria^ of Owen embracing the same 

 animals as the Protozoa of Siebold, his Entozoa^ the same as the A'^ermes, and his 

 Radiaria the same as the Zoophyta, with the single exception that Owen refers 

 the Annellata to the province of Articulata, whilst Siebold includes them among 

 his Vermes. Beyond this the types of Mollusca and Articulata (Arthropoda) of 

 the two distinguished anatomists entirely agree. The position assigned by Owen 

 to the provinces Articulata and Mollusca, not one above the other, but side by 

 side with one another,* is no doubt meant to express his conviction, that the com- 

 plication of structure of these two types does not justify the idea that either 

 of them stands higher or lower than the other ; and this is perfectlj^ correct. 



Several groups, established ]?y previous writers as families or orders, are here 

 admitted as classes. His class Epizoa, which is not to be confounded with that 

 established by Nitzsch under the same name, corresponds exactly to the family 

 called Lernees by Cuvier. His class Hydrozoa answers to the order Hydroida of 

 Johnston, and is identical with the class called Dimorpilea by Ehrenberg. His 

 class CcELELMiNTHA Corresponds to the order of Intestinaux Cavitaires established 



^ I have given precedence to the classification 

 of Owen over those of von SiehoM and Stannius, 

 Milne-F^Jwards, Leuckart, etc., hecausc tlie first edi- 

 tion of tlie " Lectnres on Coiiiparative Anatomy " 

 was pnlilished in 181.'?; hut in estimating its features, 

 as expresse<I in the preceding diagram, it should be 

 borne in mind that, in the first edition, lh<' cliisse3 

 alone are considered, and that the orders and families 

 were oid\' adiled to the seconil edition in IK.").'). I 

 mention tiiis sim|)ly to prevent the possibility of 

 being understood as ascribing to Owen all those sub- 

 divisions of the classes, which he admits, and which 

 do not appear in the systems considei'cd before his. 



'^ The Tvhizopoda are considered as a group 

 coequal to Hotifera and Polygastria, on p. 10 of 

 the " Lectures," but on p. 59, thev stand a-s a sub- 

 order of Polygastria. 



° The Turbellaria are represented as an inde- 

 pendent group, on p. If), and referred as a suborder 

 to the Tremaloda, on p. 118. 



* From want of room, I liave been compelled, 

 in reproducing the classification of Owen in the 

 preceding diagram, to place hi.s provinces Articulata 

 and Mollusca one below the other upon my page ; 

 according to his views, they should stand on a level, 

 side by side with one another. 



