1. A method of teaching Octopus chemotactile discriminations is described.
2. The animals can be shown to be capable of distinguishing by touch between porous objects soaked in plain sea water and sea water with hydrochloric acid, sucrose or quinine sulphate added.
3. They can detect these substances in concentrations at least 100 times as dilute as the human tongue is capable of detecting them in distilled water.
4. They can be trained to distinguish between equimolar (0.2 mM) solutions of hydrochloric acid, sucrose and quinine.
5. They can also be trained to distinguish between sea water and fresh water or half-strength sea water or sea water with twice the usual quantity of salt.
6. The function of the ‘olfactory organ’ is discussed.
7. Chemotactile learning is discussed in relation to the means by which Octopus finds its way about the territory around its ‘home’