2 2 CHORDATE ANATOMY 



CLASSIFICATION OF ANIMALS— SUMMARY 

 Animal Phyla 



1. Protozoa. Unicellular. Reproduce by fission. 



METAZOA, multicellular. 



2. Porifera. Multicellular. Acoelomate. Pores in body-wall. 



3. Coelenterata. Multicellular. Acoelomate. Radial symmetry 

 may possibly disguise primitive bilateral symmetry. Two-layered body- 

 wall. Nettling-cells. Enteron with single opening. 



4. PL.A.TYHELMINTHES. Bilateral. Flat-bodied. Without coelom. 

 Anus in a few genera. 



5. Nemathelminthes. Pseudocoelomate. Cylindrical. Anus. 



6. Molluscoida. Usually coelomate. U-shaped alimentary canal. 

 Lophophore. 



7. Rotifera. Pseudocoelomate. Trochophore-like worms. Cilia 

 around mouth. 



8. Echinodermata. Coelomate. Spiny-skinned. Water-vascular 

 system. Bilateral symmetry disguised. 



9. Annelida. Coelomate. Metameric. Appendages, when present, 

 without joints. 



10. MoLLUSCA. Coelomate. Non-metameric. Mantle, mantle-cav- 

 ity, foot. 



11. Arthropoda. Pseudocoelomate. Metameric. Jointed append- 

 ages. 



Classes, Crustacea, Arachnida, Onychophora, Myriapoda, Insecta. 



12. Chordata. Notochord. Dorsal tubular nervous system. 



Sub-Phyla of Chordates 



Hemichorda. Notochord limited to oral and pre-oral region. Worm- 

 like. Body in three primary divisions. Balanoglossus. 



Urochorda. Notochord limited to tail region. Body-wall covered 

 with cellulose sac. Appendicularia, Ascidia. 



Cephalochorda. Notochord in head, trunk, and tail throughout 

 life. Metameric. Amphioxus. 



Hemichorda, Urochorda and Cephalochorda together are often called 

 protochordates. 



Vertebrata. Chordates with brain case and vertebrae. Squalus. 



Classes of Vertebrates (Craniota) 

 I. Cyclostom.\ta. Without paired appendages or biting jaw. Usu- 

 ally hermaphroditic. Petromyzon, Myxine, Bdellostoma. 



