Nature of the sites inhabited — Can live long under water — Nocturnal — Wander about at night — Often lie close to the mouths of their burrows, and are thus destroyed in large numbers by birds — Structure — Do not possess eyes, but can distinguish between light and darkness — Retreat rapidly when brightly illuminated, not by a reflex action — Power of attention — Sensitive to heat and cold — Completely dtaf — Sensitive to vibrations and to touch — Feeble power of smell — Taste — Mental qualities — Nature of food — Omnivorous — Digestion — Leaves before being swallowed, moistened with a fluid of the nature of the pancreatic secretion — Extra-stomachal digestion - Calciferous glands, structure of — Cal- careous concretions formed in the anterior pair of glands — The calcareous matter primarily an excretion, but secondarily serves to neutralise the acids generated during the digestive process.