Classification Of Animals

Water vascular system is a division of the coelom and most distinctive feature of echinoderms. It is a system of canals and body wall appendages and also term as ambulacral system which functions as a means of locomotion. It consists of sieve plates, stone canal, water ring or ring canal, radial canals and podia or tube feet.

The body cavity (coelom) of earthworm is filled with an alkaline, colourless or milky coelomic fluid containing water, salts some proteins and four types of coelomic corpuscles, i.e., phagocytes, mucocytes, circular nucleated cells and chloragogen cells. During burrowing, the coelomic fluid becomes turgid and acts as hydraulic skeleton.

Uricotelism means uric acid is present in excretion. This type of excretion is present in organism which develop in an enclosed egg or, which withstand with a very dry terrestrial environment as adult organism. uric acid is discharged as a solid pallet or as a thick paste. It is most commonly found in birds, terrestrial reptiles, insects, gastropods and in some molluscs etc.