232 



HOW DO WE CLASSIFY ANIMALS? 



T. F. 4. Examples of coelenterates are sea anemones and starfish. 



T. F. 5. The Platyhelminthes are the roundworms. 



T. F. 6. An example of an annulata is an earthworm. 



T. F. 7. The earthworm has a digestive tract inside the body cavity 



T. F. 8. Starfish are echinoderms. 



T. F. 9. The Xemathelminthes are the roundworms. 



PROBLEM HI. WHAT ARE THE CHARACTERISTICS OF THE 

 ARTHROPODS? 



Arthropoda (Gr. arihros, joint ; pous, foot). All animals which 

 are jointed, have limy or chitinous exoskeletons, and jointed 

 appendages belong to this phylum, Arthropoda. They live in 

 water, or on land, or in the air. Most of them undergo a meta- 

 morphosis. There are about 500,000 known species, more than all 

 the rest of the animal kingdom put together. These animals are 

 similar to the annelids or worms in that their bodies are composed 

 of a number of segments. 



OnychcfphoTra 



peripetias 



Arachxiida 



Spider- 



CrustcrCecx 



Inseotcc 



: }*lVriapoc£ac 



<M*^cct> 



c£ig<ger* N/ctS"p 



CentipecCe 



Class I. Onychophora. These are simple wormlike animals. They live on land. 



Class II. Myriapoda (thousand legs'). They have long bodies with many segments and many 

 paired jointed appendages. Centipedes and millepedes are examples. 



Class III. Crustacea. Thev live mostlv in the water and breathe by means of gills. lne 

 head and thorax are fused 'into a hard covering. They have a " crusty " exoskeleton, strength- 

 ened with lime. Examples : crabs and lobsters. . 



Class IV. Insecta. The largest of all classes of animals (over 450,000 species). Body 

 segmented ; three regions : head, thorax, and abdomen. Three pairs of jointed legs. 

 Usually compound eves. Breathe through tracheae or air tubes. 



Class V. Arachnida (a-rak'nl-da) . This group has no antennae, four pairs of legs, and a pair 

 of claw-like appendages on each side of the mouth. Head and thorax combined as in 

 Crustacea. The spiders, "daddy-long-legs," scorpions, mites, and ticks are in this class. 



