GENERAL CLASSIFICA TION 



125 



KEY TO THE BRANCHES, OR SUB-KINGDOMS 



Aj One-celled Animals {Protozoans) 

 A., Many-celled Animals {Metazoans) 



Bj Radiate (around a center). Without 

 head : all aquatic, resembling plants, and 

 often fixed to bottom 



C\ Walls of body serving as digestive 

 organs 



D 1 Many openings, no tentacles 



D 2 One opening, which is both 

 mouth and vent ; tentacles for 

 seizing prey 

 C, Digestive tube distinct from body 

 wall, spiny skin 

 B 2 Bilateral. With anterior and posterior 

 end ; dorsal and ventral surface 



C l Body of successive segments ; legs 



without joints 

 C 2 External skeleton of successive 



rings ; jointed legs 

 C 3 Body soft ; no skeleton ; usually 



bearing a limy shell 

 C 4 Internal jointed skeleton, attached 

 to an axis or vertebral column 



I. Protozoans 



II. Sponges 



(Port/era) 



III. Polyps 



( Ccelenteratd) 



IV. ECHINODERMS 



V. Vermes 

 VI. Arthropods 

 VII. Mollusks 

 VIII. Vertebrates 



Examples. —Tell the branch to which each of the following animals 

 belongs : crayfish, earthworm, thousand leg, white grub, sea anemone, 

 ameba, tapeworm, caterpillar, beetle, sparrow, snake, oyster, starfish, 

 fish. Be prepared to state the reason for each classification. 



The classes in the branch vertebrata are: 1. Fishes (pisces). 

 2. Frogs and Salamanders (batrachia). 3. Reptiles (reptilia). 

 4. Birds (aves). 5. Mammals {mammalia). 



Fig. 247.— A Snail. (Which branch ? Why?) 



