SYNOPTIC KEY 



23(32) Without jointed appendages, body wormlike. 24 



24(29) Without segmentally arranged bristles. 25 



25(26) Internal parasites lacking mouth, anus and whole 



digestive tract; body long, flattened, increasing in 



size posteriorly. Segments distinct and numerous. 



Posterior ones may become free. The tape worms. 



Phylum Platyhelminthes, Class Cestoda, p. 14 



26(25) Mouth, anus, and alimentary canal present; posterior 

 end not markedly larger than anterior. 27 



27(28) Without spiracles, tracheal gills, or trachea. With a 

 sucker at each end of the body except in a few marine 

 forms. The leeches. Mainly fresh water. 



Phylum Annelida, Class Hirudinea, p. 17 



28(27) Without a sucker at each end of the body. With 

 spiracles, trachea, or tracheal gills. Trachea fre- 

 quently visible through the body wall as white lines. 

 Fleshy, unjointed prolegs, present or absent; head 

 large and conspicuous or small and retractile within 

 the body; mouth parts present. Includes forms fed 

 by other members of the colony, parasitic forms, 

 wood-borers, fresh- water and terrestrial free-living 



forms. 



Phylum Arthropoda, Larval Insecta, p. 37 



29(24) With segmentally arranged bristles. 30 



30(31) Without trachea, tracheal gills, or spiracles; in fresh- 

 water forms never with large tufts of bristles at one 

 end of the body; aquatic and terrestrial. In marine 

 forms, the bristles (setae) are borne usually on out- 

 growths of the body wall called parapodia or are rarely 

 absent. Phylum Annelida, p. 17 



31(30) With trachea, tracheal gills, or spiracles; often with 

 large tufts of bristles at one end of the body; with a 



