PERIOD OF CUVIER. 311 



CL. 4. ACEPHALA. Ord. Testacea, Tunicata. 



CL. 5. BRACHIOPODA. No subdivisions into orders or families. 



CL. 6. CIRRHOPODA. No subdivisions into orders or families. 



Third Branch. ANIMALIA ARTICULATA. 



CL. 1. ANNELIDES. Ord. Tubicolae, Dorsibranchiae, Abranchiac. 



CL. 2. CRUSTACEA. 1st Section: Malacostraca. Ord. Decapoda, Sto- 

 mapoda, Amphipoda, Laemodipoda, Isopoda. 2nd Section: 

 ENTOMOSTRACA. Ord. Branchiopoda, Poecilopoda, TrilobitEe. 



CL. 3. ARACHNIDES. Ord. Pulnionariao, Trachearise. 



CL. 4. INSECTS. Ord. Myriapoda, Thysanura, Parasita, Suctoria, Co- 



leoptera, Orthoptera, Hemiptera, Neuroptera, Ilyrncnoptera, 



Lepidoptera, Rhipiptera, Diptera. 



Fourth Branch. ANIMALIA RADIATA. 



CL. 1. ECHINODERMS. Ord. Pedicellata, Apoda. 



CL. 2. INTESTINAL WORMS. Ord. Nematoidea (incl. Epizoa and Ento- 



zoa), Parenchymatosa. 



CL. 3. ACALEPH.S. Ord. Simplices, Hydrostatics}. 

 CL. 4. POLYPI. (Including Anthozoa, Hydroids, Bryozoa, Corallinae, 



and Spongiee.) Ord. Carnosi, Gelatinosi, Polypiarii. 



CL. 5. INFUSORIA. Ord. Rotifera and Homogenea (including Polygas- 

 trica and some Algae). 



When we consider the zoological systems of the past 

 century, that of Linnaeus, for instance, and compare them 

 with more recent ones, that of Cuvier, for example, we 

 cannot overlook the fact, that, even when discoveries have 

 added little to our knowledge, the subject is treated in a 

 different manner; not merely in consequence of the more 

 extensive information respecting the internal structure of 

 animals, but also respecting the gradation of the higher 

 groups. 



Linnaeus had no divisions of a higher order than classes. 

 Cuvier introduced, for the first time, four great divisions, 

 which he called " embranchemens" or branches, under 

 which he arranged his classes, of which he admitted three 



