Proglottids are segments of a tapeworm, a type of parasitic flatworm. Each proglottid contains both male and female reproductive organs, allowing the tapeworm to reproduce. As the tapeworm grows, new proglottids are formed at the neck region, while older ones move further away from the head. These segments can detach from the main body of the tapeworm and are often expelled in the host's feces. Each proglottid can contain hundreds of eggs, which can then infect new hosts. This reproductive strategy helps ensure the survival and spread of the tapeworm species.