Solution

Clitellum is a girdle, where there are gland cells which secrete a substance which dries up to form the cocoon in which the egg is discharged and sperms too so as to ensure fertilization. In the cocoon the embryo of earthworm develops. The gizzard is located (front end to back end) after the crop in the earthworm. It is firm because it's purpose is to crush food. The gizzard is a muscle that also leads into the intestine. Setae help earthworms attach to the surface and prevent backsliding during peristaltic motion. Typhlosole function is to increase intestinal surface area for more efficient absorption of digested nutrients.