Earthworms have no skeleton but during burrowing, the anterior end becomes turgid and acts as a hydraulic skeleton. It is due to

Step-by-step solution

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, ie, phagocytes, mucocytes, circular nucleated cells and chloragogen cells. The coelomic fluid becomes turgid and acts as a hydraulic skeleton during burrowing. Earthworm (Pheretima posthuma) living in burrows which are made in moist earth. It makes its burrow partly by boring with its pointed anterior end and partly by sucking and swallowi