CuAP. III. EMBRYOLOGICAL SYSTEMS. 227 



CLASSIFICATION OF VAN BENEDEN. 



Van BciK'dcn has also proposed a classification based upon Embryology, which was first sketched in 

 his paper ui)oii the Jlmbryology of Bryozoa: Recherches sur I'anatomie, la physiologic et I'embryogenie des 

 Bryozoaires, Bruxelles, 1845, 4to., and afterwards extended in his Comparative Anatomy: Anatomie comparee, 

 Bruxelles, (without date, but probably from the year 1855,) 1 vol. 12mo. 



I. HrpocOTYLEDONEs or Hyi'Ovitellians. (Vertebrata.) The vitellus enters the body from the ven- 



tral side. 

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



boscidea, Ungulata, Sirenoidea, Cetacea.) 

 Cl. 2. Birds. (Psittaceoe, Rapaces, Passeres, Columbae, Gallinae, Struthiones, Gralte, Palmipedes.) 

 Cl. 3. Reptiles. (Crocodili, Chelonii, Ophidii, Saurii, Pterodactyl!, Simosaurl, Plesiosauri, 



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, Diptera, Orthop- 



tera, Hemiptera, Thysanura, Parasita.) 

 Cl. 7. M y r i a p o d e s . ( Diplopoda, Cliilopoda.) 

 Cl. 8. Arachnid es. (Scorpiones, Araneoe, Acari, Tardigrada.) 

 Cl. 9. Crustacea. (Decapoda, Stomapoda, Amphipoda, Isopoda, Ltemodipoda, Phyllopoda, Lophy- 



ropoda, Xiphosura, Siphonostoma, Myzostoma, and Cirripedia.) 



III. Allocotyledones or Allovitellians. (Mollusco-Radiaria.) The vitellus enters the body neither 



from the ventral nor from the dorsal side. 

 Cl. 10. Mollusca. Including Cephalopoda, Gasteropoda, Poecilopoda, and Brachiopoda. (Acephala, 



Tunicata, and Bryozoa.) 

 Cl. 11. Worms. (Malacopoda, Annelides, Siponculides, Nemertini, Nematodes, Acanthocephali, 



Scoleidcs, Ilirudinci.) 

 Cl. 12. Echinoderms. (Ilolothuria?, Echinides, Stellerides, Crinoides, Trematodes, Cestodes, 



Rotifcri, Planariai.) 

 Cl. 13. Poly J) s. Including Tunicata, Bryozoa, Anthozoa, Alcyonaria, and Medusa;, as orders. 



(Ctcnopliorffi, Siphonophora', Discophora", Ilydroids, Anthophorida;.) 

 Cl. 14. Rhizopods. Only the genera mentioned. 

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



Van Beneden thinks the clas.'*ification of Linna>ns truer to nature than either 

 that of Cuvier or of de Blainville, as tlie class of Worms of the Swedish naturahst 

 corresponds to his Allocotyledones, that of Insects to his H3'pocotyledones, and the 

 four classes of Pisces, Amphil)ia, Aves, and Mammalia to his Il3pocotyledones. 

 He compares his primary divisions to the Dicotyledones, Monocotyledones, and 

 Acotyledones of the vegetable kingdom. But he overloolis that the Cephalopods 



