Explanation

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. During burrowing and locomotion, contraction of septa (which partioned coelom into series of coelomic chambers) increases pressure on coelomic fluid, thus making the anterior body segment turgid and elongated.