In moving the tumblers the water has naturally been shaken, and the creature being alarmed will probably at first remain motionless.  But very soon it will begin to play in the water, rising and falling, and swimming gracefully from side to side.  Now you will notice a curious effect, for the bands will glitter and become tinged with prismatic colors, till, as it moves more and more rapidly these colors, reflected in the jelly, seem to tinge the whole ball with colors like those on a soap-bubble, while from the two sacs below come forth two long transparent threads like spun glass.  At first these appear to be simple threads, but as they gradually open out to about four or five inches, smaller threads uncoil on each side of the line till there are about fifty on each line.  These short tendrils are never still for long; as the main threads wave to and fro, some of the shorter ones coil up and hang like tiny beads, then these uncoil and others roll up, so that these graceful floating lines are never two seconds alike.

We do not really know their use.  Sometimes the creature anchors itself by them, rising and falling as they stretch out or coil up; but more often they float idly behind it in the water.  At first you would perhaps think that they served to drive the ball through the water, but this is done by a special apparatus.  The cross ridges which we noticed on the bands are really flat comb-like plates (p, Fig. 9), of which there are about twenty or thirty on each band; and these vibrate very rapidly, so that two hundred or more paddles drive the tiny ball through the water.  This is the cause of the prismatic colors; for iridescent tints are produced by the play of light upon the glittering plates, as they incessantly change their angle.  Sometimes they move all at once, sometimes only a few at a time, and it is evident the creature controls them at will.

This lovely fairy-like globe, with its long floating tentacles and rainbow tints, was for a long time classed with the jelly-fish; but it really is most nearly related to the sea-anemones, as it has a true central cavity which acts as a stomach, and many other points in common with the Actinozoa.  We cannot help wondering, as the little being glides hither and thither, whether it can see where it is going.  It has nerves of a low kind which start from a little dark spot (ng) exactly at the south pole of the ball, and at that point a sense-organ of some kind exists, but what impression the creature gains from it of the world outside we cannot tell.

I am afraid you may think it dull to turn from such a beautiful being as this, to the gray leaf which looks only like a dead dry seaweed; yet you will be wrong, for a more wonderful history attaches to this crumpled dead-looking leaf than to the lovely jelly-globe.

[Illustration:  FIG. 10.  THE SEA-MAT OR FLUSTRA (Flustra foliacea).

1, Natural size. 2, Much magnified, s, Slit caused by drawing in of the animal a.]