Diversions of a naturalist (1915) Diversions of a naturalist diversionsofnatu00lank Year: 1915 94 DIVERSIONS OF A NATURALIST The transparency and colourlessness of marine animals which float near the surface is, on the other hand, obviously useful, and to this group our jelly-fishes belong. Not only do they escape observation by their transparency and general absence of colour, but some actually have a blue transparent colouring which blends with the blue colour of the sea. Such are the gas- holding, bladder-like sac as large as your fist called the ' Portuguese man-of-war,' and the little s
Diversions of a naturalist (1915) Diversions of a naturalist diversionsofnatu00lank Year: 1915 94 DIVERSIONS OF A NATURALIST The transparency and colourlessness of marine animals which float near the surface is, on the other hand, obviously useful, and to this group our jelly-fishes belong. Not only do they escape observation by their transparency and general absence of colour, but some actually have a blue transparent colouring which blends with the blue colour of the sea. Such are the gas- holding, bladder-like sac as large as your fist called the ' Portuguese man-of-war,' and the little sailing Velella, both of which float, and even protrude above the surface, so as to catch the wind. Others are only semi-transparent, and others are marked with strong red, brown, or yellow streaks. Many of the smallest kinds of jelly-fish have eyes which are bright red in colour. The animals to which the name ' jelly-fishes ' is now more or less strictly applied are (as that fine zoologist Aristotle knew) in their struc- ture closely similar to the sea-anemones, but even simpler. They are called the Medusae by naturalists. Their disk-like bodies are largely formed by a jelly-like material, on the surface of which are stretched delicate transparent skin, nerves, and delicate muscles, whilst in the middle of the disk, on the surface which faces downwards as the creature floats, is the mouth, leading into a relatively small pouched cavity excavated in the jelly, from which a delicate system of canals is given off, and radiates in the jelly of the disk. There is, as in the sea-anemones, only one continuous cavity. The edge of the disk is beset with fine, sensitive tentacles, sometimes many feet Fig. 7.—A common British Jelly-fish. Aurelia aurita, usually as large as a breakfast-plate and often larger.
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