Final answer:
The glandular epidermis of acorn worms secretes mucus and other substances for functions like locomotion, feeding, and environmental interaction, but the exact substances are not specified in the reference provided.
Step-by-step explanation:
The glandular epidermis of acorn worms, particularly around the proboscis tip and collar, secretes mucus and various other substances. These secretions are critical for a variety of functions including locomotion, feeding, and interaction with the environment. This mucus acts as a lubricant, allowing the acorn worm to burrow and move smoothly through the sediment. It also aids in the collection of food particles by sticking them together before ingestion. Additionally, some glands may secrete substances that offer protection or participate in other biological processes such as osmoregulation and defense mechanisms. However, the reference provided does not specifically state the substances secreted by acorn worms.