Q.Describe the digestive system and the process of digestion in Pheretima.

[!TLDR] Pheretima's gut runs mouth to buccal cavity, pharynx, oesophagus, crop, gizzard, stomach-intestine (with typhlosole), to anus. …

[!ANSWER] The alimentary canal of Pheretima runs the full length of the body as a single tube, divided into a sequence of distinct, specialised regions.

Food — chiefly organically rich soil — is taken in through the mouth at the anterior end, just beneath a small overhanging lobe, the prostomium. The mouth opens into a short, muscular buccal cavity, followed by the pharynx, which acts as a suction organ, actively helping to draw soil and food particles into the gut.

Behind the pharynx lies a narrow oesophagus, which in Pheretima bears calciferous glands — these secrete calcium carbonate, thought to help neutralise the excess acidity generated by decaying organic matter present in the ingested soil. The oesophagus leads into a thin-walled, distensible crop, which functions mainly as a temporary storage chamber for the ingested soil, and then into a thick-walled, muscular gizzard, which mechanically grinds the food and soil particles fine (assisted by the grit of the soil itself) before they pass on for chemical digestion. …

• Mixing up the order of the crop (storage) and gizzard (grinding) — the crop always precedes the grinding gizzard. …