104 



ELEMENTS OF BIOLOGY 



CTENOPHORA 



PLA TYHELMINTHES 



BAND OF 

 CILIA 



MOUTH 



PHAftYNX 



INTESTINE 



MOUTH 



FIG. 36. COMB JELLV 



FIG. 37. PLAN ARIA 



PL A TrHEL MIN THES 



VENTRAL 

 SUCKER 



ORAL SUCKER 



HOOKS 

 SUCKER 



INTESTINE 



HEAD OR SCOLEX 



PROGLOTTID 



FIG. 36. LIVER FLUKE FIG. 39. HUMAN TAPEWORM 



Fig. 36. — An example of the phylum Ctenophora, showing external characters only. 

 Figs. 37, 38, and 39. — Representatives of the three classes of the phylum Platyhel- 

 minthes. Planaria are common free living forms, mostly aquatic. The flukes are 

 parasitic in the liver, blood vessels, lungs, bladder, and elsewhere in vertebrate 

 animals. Tapew^orms are parasites inhabiting the intestines of vertebrates. 



