“The tentacles were entirely composed of the same soft, jelly-like substance as that of the envelope, and every part was iridescent in a sort of vapoury transparent cloud of many-tinted colours, blue and pale crimson predominating. I have filled up to the best of my memory the little sketch, and only wish you could have seen the Velellas as I did, in their full life and beauty.” Two of the specimens here mentioned are in my collection, and beautiful little things they are. The two plates are not thicker than ordinary silver paper, but are wonderfully strong, tough, and elastic. The oval horizontal plate, or raft, if it may be so called, is strengthened by being corrugated in concentric lines, and having a multitude of very fine ribs radiating from the centre to the circumference. It is slightly thickened on the edges, evidently for the attachment of the tentacles. The perpendicular plate, or sail, does not occupy the larger diameter of the raft, but stretches across it diagonally from edge to edge, rising highest in the centre and diminishing towards the edges, so that it presents an outline singularly like that of a lateen sail. It is rather curious that the magnifying glass gives but little, if any, assistance to the observer, the naked eye answering every purpose. Even the microscope is useless, detecting no peculiarity of structure. I tried it with the polariscope, scarcely expecting, but rather hoping, to find that it was sensitive to polarised light. But no such result took place, the Velella being quite unaffected by it. The corresponding illustration is a sketch of a raft to which a sail is attached. Such rafts as this are in use in many parts of the world, the sail saving manual labour, and the large steering oar answering the double purpose of keel and rudder. In the Velella, the tentacles, though they may not act in the latter capacity, certainly do act in that of the former, and serve to prevent the little creature from being capsized in a gale of wind. THE BOAT. There is no doubt that the first idea of locomotion in the water, independently of swimming, was the raft; nor is it difficult to trace the gradual development of the raft into a Boat. The development of the Kruman’s canoe into the _Great Eastern_, or a modern ironclad vessel, is simply a matter of time. It is tolerably evident that the first raft was nothing more than a tree-trunk. Finding that the single trunk was apt to turn over with the weight of the occupant, the next move was evidently to lash two trunks side by side. Next would come the great advance of putting the trunks at some distance apart, and connecting them with cross-bars. This plan would obviate even the chance of the upsetting of the raft, and it still survives in that curious mixture of the raft and canoe, the outrigger boat of the Polynesians, which no gale of wind can upset. It may be torn to pieces by the storm, but nothing can capsize it as long as it holds together.