giving the healthy animal, when busy in its proper element, a very curious appearance. Though the jelly-fish is in constant motion--in perpetual motion, so to speak, for it never rests, that ever we could discover, either by night or day--its progress in the sea is rather due to the set of the wind and the tide-drift than its own exertions, its incessant labours of contraction and expansion being performed not so much for the purpose of shifting its place in the water, as for the purpose of grasping and sucking in at each contraction such microscopic organisms as form its food. It is true that in a calm and tideless sea its motions cause it to be carried in the direction of the contracting beat an inch or thereby at a time, but this progress is clearly accidental and unintentional, so far as it is concerned, the great object of the incessant contraction and expansion being, as we have said, not so much change of place as the capture and insuction of its ordinary food. The Medusæ swim at all depths in the sea, but as a rule they seem to prefer feeding within a fathom or two of the surface, particularly if the sun is bright and the sea is perfectly calm. The mouth of the Medusa is in the centre of the under concave surface, and the animal's modus operandi in sweeping in its food towards this orifice is not difficult to understand. Stretch out your right hand, with its back or knuckle surface uppermost. First expand the hand and fingers to their full extent, then contract so as almost, but not quite, to close the hand, not quickly, but very firmly and decidedly. Continue in this way opening out and closing the hand and fingers, not quite so fast as a second's beating pendulum oscillates, and you have the perfect analogue, or more properly the homologue, of the Medusa's action. If you can fancy an orifice or mouth in the centre of your palm, and your fingers to be the fringe surrounding the jelly-fish disc, and if you perform the action indicated in a tub or pool of water, into which a little flour or fine oatmeal has been thrown to represent the animalculæ forming the Medusa's food, so much the better: you will at once understand how the animalculæ and food particles are swept and sucked in by the current created towards the animal's mouth, or gastric cavity, as it might be more properly termed. When one or more of these animals comes in contact with a swimmer's skin, the sensation is anything but agreeable, a feeling of indescribable loathing and horror being engendered by the touch of the cold, gelatinous mass, that you are yet conscious is not dead matter, but an animated pulsating organism. But though contact with the ordinary Medusa is bad enough, there is another species of jelly-fish not uncommon in British waters at certain seasons, accidental contact with which is a very serious matter indeed. These are known to naturalists as Acalephæ, from a Greek word signifying a nettle. They are not so numerous on our shores as the true Medusa,