Jelly-fish seek the light, and they can be made to follow a bright light from one side of the aquarium to the other by manipulating the light in the proper manner. Even where a slight current is set up in the water, they will swim against it in their efforts to reach the light. When two or more of the marginal bodies are excised, no effect seems to follow such excision, but as soon as the last of these bodies is cut out, the creature falls to the bottom of the tank without motion. When a point in the nectocalyx is irritated with a point of a needle or by a vegetable or mineral irritant, the tip of the manubrium will turn toward, and endeavor to touch, the spot irritated. It does not turn at once, as it would were its movements the result of reflex action; it moves deliberately as though actuated by volition. The above experiments and observation seem to indicate the presence of conscious determination in the medusa; in fact, there seems to be a distinct element of choice in these psychical manifestations. While engaged in watching a water-louse, I saw it swim to a hydra, tear off one of its buds, and then swim some distance away to a small bit of mud, behind which it hid until it devoured its tender morsel. Again it swam back to the hydra and plucked from it one of its young; again it swam back to the little mud heap, behind which it once more ensconced itself until it was through with its meal. When we remember that this little creature was among entirely new surroundings (for I dipped it from a pond in a tablespoon full of water which I had poured into a saucer), we will appreciate the fact that the water-louse evinced conscious determination and no little memory. It probably discovered the hydra accidentally; it then, as soon as it had secured its prey, swam away, seeking some spot where it could eat its food without molestation. But when it sought the hydra again and swam back to its sheltering mud heap, it showed that it remembered the route to and from its source of food supply and its temporary hiding-place.