PRINCIPAL SYSTEMS OF ZOOLOGY 253 



I. HvpocoT\xEDONES or Hypovitellians. (Vertebrata.) The vitclliis enters the body from 



the ventral side. 

 Cl. 1. Mammalia. (Primates, Cheiroptera, Insectivora, Rodentia, Carnivora, Edentata, 



I'roljoscidea, Ungulata, Sircnoidea, Cetacca.) 

 Cl. 2. Birds. (Psittaces, Rapaccs, Passeres, Columbic, Gallinas, Struthiones, Grallae, 



Pahiiipedes.) 

 Cl. 3. Reptiles. (Crocodili, Chelonii, Ophidii, Saurii, Pterodactyl!, Simosauri, Plesio- 



sauri. Ichthyosauri.) 

 Cl. 4. Batrachians. (Labyrinthodontes, Peromelia, Anura, Urodela, Lepidosirenia.) 

 Cl. 5. Fishes. (Plagiostomi, Ganoidei, Teleostei, Cyclostomi, Leptocardii.) 



II. Epicotyledones or Epivitellians. (Articulata.) The vitellus enters the body from 



the dorsal side. 

 Cl. 6. Insects. (Coleoptera, Nevroptera, Strepsiptera, Hymenoptera, Lepidoptera, Dip- 



tera, Orthoptera, Hemiptera, Thysanura, Parasita.) 

 Cl. 7. Myriapodes. (Diplopoda, Chilopoda.) 

 Cl. 8. Arachnides. (Scorpiones, Araneas, Acari, Tardigrada.) 

 Cl. 9. Crustacea. (Decapoda, Stomapoda, Amphipoda, Isopoda, Lsemodipoda, Phyllo- 



poda, Lophyropoda, Xiphosura, Siphonostma, Myzostoma, and Cirripedia.) 



III. Allocotvledones or Allovitellians. (Mollusco-Radiaria.) The vitellus enters the 



body neither from the ventral nor from the dorsal side. 



Cl. 10. MoIIusca. Including Cephalopoda, Gasteropoda, Poecilopoda, and Brachiopoda. 



(Acephala, Timicata, and Bryozoa.) 

 Cl. 11. Worms. (Malacopoda, Annelides, Siponculides, Nemertini, Nematodes, Acan- 



thocephali, Scoleides, Hirudinei.) 

 Cl. 12. Echinoderms. (Holothuriae, Echinides, Stellerides, Crinoides, Trematodes, Ces- 



todcs, Rotiferi, Planariac.) 

 Cl. 13. Polyps. Including Tunicata, Bryozoa, Anthozoa, Alcyonaria, and Medusae, as 



orders. (Ctenophoras, Siphonophorae, Discophorae, Hydroids, Anthophoridae.) 

 Cl. 14. Rhizopods. Only the genera mentioned. 

 Cl. 15. Infusoria. Only genera and families mentioned. 



Van Beneden thinks the classification of Linnseiis truer to nature 

 than either that of Cuvier or of de Blainville, as the class of Worms 

 of the Swedish naturalist corresponds to his Allocotyledones, that 

 of Insects to his Hypocotyledones, and the four classes of Pisces, 

 Amphibia, Aves, and Mammalia to his Hypocotyledones. He com- 

 pares his primary divisions to the Dicotyledones, Monocotyledones, 

 and Acotyledones of the vegetable kingdom. But he overlooks that 

 the Cephalopods are not Allocotyledones, and that any group of ani- 

 mals which unites Mollusks, Worms, and Radiates in one great mass 

 cannot be founded upon correct principles. As to his classes, I can 

 only say that if there are natural classes among animals, there never 

 was a combination of animals proposed since Linnaeus less likely 

 to answer to a philosophical idea of what a class may be than that 

 which unites Tunicata with Polyps and Acalephs. In his latest work 

 Van Beneden has introduced in this classification many important 



