KEY TO PHYLA 15 



5. (4) Body radially symmetrical; body wall not pierced 

 by pores. Body composed essentially of two layers of cells with- 

 out a cavity between them. Inner layer forms digestive system. 

 Anus wanting. Parts of the body not usually arranged in five 

 or multiples of five. PHYLUM COELENTERATA (see page 16) 



6. (3) Body usually bilaterally symmetrical, or in part spiral- 

 ly coiled, never radially symmetrical 7 



7. (15) Body not divided into segments. (In determining 

 this point examine various surfaces of the body. Wings and 

 other structures frequently obscure evidences of segmentation 

 on the dorsal surface) 8 



8. ( 1 1 ) Body usually large, not worm-like 9 



9. ( 10) Completely or partially encased in a limy shell com- 

 posed of one or two pieces. Soft parts of body inside shell either 

 bilaterally symmetrical or in part spirally coiled. Ventral surface 

 provided with a heavy muscular locomotor organ, the foot. 



PHYLUM MOLLUSCA (see page 17) 



10. (9) With an axial skeleton consisting of a skull and ver- 

 tebral column. Nearly always with two pairs of jointed appen- 

 dages. Central nervous system entirely dorsal to alimentary ca- 

 nal. PHYLUM CHORDATA, SUB-PHYLUM VERTEBRATA- (see page 22) 



11. (8) Body small, worm-like, not provided with shell, skel- 

 eton, or j ointed appendages : 1 2 



12. (13) Body flattened dorso-ventrally. Alimentary canal 

 consisting of a pharnyx and a branching intestine without any 



anUS. PHYLUM PLATHELMINTHES _ (see page I 1 /) 



13. (12) Body cylindrical or flattened. Alimentary canal 

 always terminating posteriorly in an anal opening 14 



14. (15) Body not segmented, covered with cuticula. 



PHYLUM COELHELMINTHES, CLASS NEMATHELMINTHES 



(see page 17) 



15. ( 7 ) Body segmented 1 6 



16. (19) Without jointed appendages; worm-like 17 



