DOMAIN OF EVOLUTIONARY HYPOTHESIS 119 



(b) Bodies four to six-rayed ; possess ^ Cnidaria (3) 



stinging cells J (Polyps and Medusae). 



2. Body cavities (at least as a split) ; 



Coelomata : 



Echinodermata (4) 



(Sea Urchins, Starfish) 



(a) Body five-rayed (symmetrical) ; 



body wall strengthened with a 

 lime skeleton 



(b) Body laterally symmetrical, bi- 



lateral : 



(a) Central nervous system is not 

 a dorsal tube ; no internal 

 axial skeleton : 



A. Body without limbs, or, 



limbed, without divided ex- j- Vermes (Worms) (5) 

 tremities 



B. Bodies without limbs, with \ 



r Mollusca (6) 



three pairs mam ganglia . , ., 



\> x HSoft animals, Snails, 

 (nerve cell agglomerations) i v . , 



-^ t u 11 Squids, etc.) 



with toot, mantle, and shell } 



C. Bodies limbed with divided) Arthropoda (7) 



extremities / (Insects, Spiders, Crabs) 



(ft) Central nervous system in 

 spine ; bodies limbed : 



A. As axial skeleton only a chorda 



dorsalis (dorsal chord, a soft \ 

 rod); Chordata Tunicata (8) 



Limbs and Chorda confined ( (Mantelthiere, Seeschei- 

 to hinder parts of body j den). 



Limbs extend throughout the ( ^eptocardii ( 9 ) 

 b I (e.g. Amphioxus, the 



Lancelet fish) 



B. With the Chorda is associated ) y ertebrata / 10 j 



the spinal column and the (the y ertebrates) 

 skull / 



