12 



Phylum PLATYHELMINTHES 



The Platodes or Flat-worms 



The flat-worms are bilaterally symmetrical animals, which are 

 devoid of true metameric segmentation, and which have no body 

 cavity between the alimentary canal and the integument. There 

 is no blood- vascular system; but there is an excretory (water- 

 vascular) system. The alimentary canal when present has only a 

 single opening, and is much branched. 



Class Trematoda — Parasitic flat-worms, without a covering of cilia 

 in the adult state, with a well-developed digestive apparatus, 

 and with the mouth at the cephalic end of the body. The liver- 

 fluke is an example of this class. 



Class Turbellaria — Non-parasitic flat-worms, with a ciliated epider- 

 mis. Not discussed. 



Class Cestoda — Endo-parasitic flat-worms, without cilia, and with- 

 out a digestive cavity; usually becoming segmented by budding. 

 This class includes the tapeworms. 



Phylum NEMATHELMINTHES 



The Thread Worms 



The body is cylindrical, spindle-shaped, or threadlike, unseg- 

 mented, and covered with a thick cuticle; the body cavity is usually 

 spacious. 



Class Nematoda — Possess a complete alimentary canal. To this 

 class belong most of the thread worms. The most familiar 

 examples are Ascaris, Oxyuris, and Trichina. 



Class Acanthocephala — Lack alimentary canal; possess a protrusible 

 proboscis which is covered with many rows of recurved hooks. 



Phylum ECHINODERMATA 



' Not discussed in this course. 



Phylum MOLLUSCOIDA 



Not discussed in this course. 



