General characteristics of Platyhelminthes:

(i) Their body is bilaterally symmetrical and dorsoventrally flattened.

(ii) They are acoelomate and triploblastic animals i.e. their tissues differentiate from three embryonic germ layers.

(iii) Circulatory and respiratory systems and skeleton are absent.

(iv) Their excretory system consists of blind tubules called protonephridia. Blind end of a tubule bears a tuft of cilia or a flagellum called the flame cell.

(v) They are hermaphrodites i.e. both male and female reproductive organs occur in the same individual.

Examples: Liver fluke (Fasciola) and blood fluke (Schistosoma)

General characters of Nematoda:

(i) They are bilaterally symmetrical, triploblastic, pseudocoelomate and unsegmented animals.

(ii) They have a cylindrical or flattened, worm-like body. Their body is covered with a tough, resistant cuticle.

(iii) Sexes are separate.

(iv) Alimentary canal straight and complete with mouth and anus.

(v) Parasitic nematodes are pathogenic and are responsible for diseases such as elephantiasis (Wuchereria bancrofti), ascariasis (Ascaris) and enterobiasis (Enterobius).