IX THE HISTOEY AND SCOPE OF ZOOLOGY 329 



Class II. Crttstacea. 



Orders : (a) Malacostraca : Decrq^oda, Stomapoda, Am- 

 phipoda., LcEinodipoda, Isopoda ; (b) Entomostraca : 

 Branchiopoda, Pcecilojjoda, Trilohitce. 

 Class III. Arachnides. 



Orders : Pulmonarice, Trachearice. 



Class lY. Insects. 



Orders : Myriapoda, Thysanura, Parasita, Suctoria, Coleo- 

 ptera, Orihoptera, Hemiptera, Neiiroptera^ Hymenoptera, 

 LepidojDtera, Rhijnptera, Diptera. 



Fourth Branch. Animalia Radiata. 



Class I, ECHINODERMS. 



Orders : Pedicellata, Apoda. 

 Class II. Intestinal Worms. 



Orders : Nematoidea^ Parencliymatosa. 

 Class III. Acaleph^. 



Orders : Simplices, Hydrostatiae. 

 Class IV. Polypi (including the Coelentera of later authorities 

 and the Polyzoa). 



Orders : Carnosi, Gelatinosi, Polypiarii. 

 Class V. Infusoria. 



Orders : Rotifera, Homogenea (this includes the Protozoa 

 of recent writers and some ProtophyUi). 



The leading idea of Cuvier, his four emhranche- 

 mens, was confirmed by the Russo-German naturalist 

 Von Baer (1792-1 8 76), who adopted Cuvier's divisions, 

 speaking of them as the peripheric, the longitudinal, 

 the massive, and the vertebrate types of structure. 

 A^on Baer, however, has another place in the history 

 of Zoology, being the first and most striking figure in 

 the introduction of Embryology into the consideration 

 of the relations of animals to one another. 



Cuvier may be regarded as the zoologist by whom 

 anatomy was made the one important guide to the 

 understanding of the relations of animals. But it 

 should be noted that the belief, dating from Malpighi 



