Page 1 : PHYLUM-PLATYHELMINTHES, , 13., , General characters, •, •, •, •, •, •, •, •, •, •, •, •, •, , These are commonly known as Flat worm., The body is dorsoventrally flattened, unsegmented andsmooth., Most of these animals are marine while few are fresh water form., These are generally parasites; few of them are free living. These are diploblastic and, bilaterally symmetrical., Free living form have disc like organs called suckers, hooks for attachment, These are acoelomates, distinct coelom is absent., The alimentary canal is present but with one opening., The mouth is present but anus is absent., Excretion and osmoregulation takes place by means of flame cells., The nervous system is well developed, it consist nerve ring and nerves., Reproductive system is well developed and complex., Most of them are hermaphrodite., Most of them are parasitic form having complicated life cycle, shows different larval, stages in different host., , PHYLUM - PLATYHELMINTHES, , CLASS - TURBELLARIA, These are free swimming., Adhesive organs present., Epidermis partly cilliated., Alimentory canal is not, forked., Ex. Planaria, , CLASS - TREMATODA, These are parasitic mostly, endoparasitic, Well developed suckers., Alimentory canal is forked., Ex.Liverfluke., , CLASS-CESTODA, These are endoparasitic., Well developed cuticle., Alimentory canal absent., Ex.Taenia solium

Page 3 : PHYLUM-NEMATOHELMINTHES, General characters, •, •, •, •, •, •, •, •, •, •, •, •, •, , These are commonly known as Round worms, thread worms., These are widely distributed in aquatic, terrestrial and free living or parasitic form., Body is cylindrical, elongated, unsegmented and vermiform., These are bilaterally symmetrical and tapering at both ends., Body is covered with resistant, flexible and elastic cuticle., These are triploblastic animals. Appendages are absent; locomotion takes place by, means of muscles., Body cavity is not well developed i.e. true coelom is absent; hence it is called, pseudocoelom., An alimentary canal is simple and straight .it start as mouth and ends in anus., Nervous system consists of a cerebral nerve ring surrounding the oesophagus and, longitudinal nerve cord extending posteriorly., Sense organs are poorly developed and are present in the form of small papillae and, amphids., Sexes are separate, showing distinct sexual dimorphism., Males are favour and smaller than female., Posterior end of male is curved while in female, it is straight., , PHYLUM - NEMATOHELMINTHES, , CLASS -NEMATODA, Alimentory canal is straight., Cuticle is well developed., Ex. Ascaris, , 15