SPECIAL PART. 



Systematic View. 



The Animal Kingdom may be classified as follows : — 



Sub-Kingdom I. : Protozoa. 



Unicellular animals : they may be colonial, but then the 

 members of the colony are essentially alike. 



Sub-Kingdom II. : Metazoa. 



Multicellular animals : the cells are differentiated (division of 

 abour) ; alimentary canal, nervous and muscular systems, etc. The 

 Metazoa are subdivided into the following Phyla :^ 



Phylum 1. Coelentera. — Radiate animals of a very simple 

 structure ; body saccular, composed of three layers enclosing a 

 •digestive cavity. No anus. No body-cavity. The different organs 

 present elsewhere in the Metazoa are but slightly indicated here. 

 — Appendix : Sponges. 



Phylum 2. Bchino derma. — Radial symmetry. Body-cavity. 

 Specialised systems of organs. Calcifications in the body-wall. A 

 vascular system. A special water vascular system in connection 

 with tube-feet. Larva bilateral. 



Phylum 3. Platyhelminthia. — Bilaterally symmetrical, 

 Tinsegmented animals, without body-cavity ; usually without vascular 

 system or anus. A branched excretory apparatus with peculiar 

 terminations. — Appendix : Rotifera. 



Phylum 4. Nemathelminthia. — Bilaterally symmetrical, 

 unsegmented animals of a cylindrical shape, with body-cavity and 

 anus. 



Phylum 5. Annelida. — Bilaterally symmetrical, segmented 

 animals, with relatively similar segments. Limbs, when present, 

 unjointed. Thin cuticle. Body-cavity, vascular system (usually), 

 and anus present. Segmented ventral nerve cords, connected with 

 a pair of ganglia lying above the pharynx. Eyes feeble. A pair 

 ■of tubular excretory organs in most segments (segmental organs). 

 — Appendix : Polyzoa, Brachiopoda. 



Phylum 6. Arthropod a. — Bilaterally symmetrical segmented 

 animals, with variously modified somites. Limbs jointed. Dermal 

 skeleton formed from a well-developed cuticle. Body-cavity. Heart 



G 2 



