Nature is full of surprises, and the greatest of these almost always arise out of the most commonplace looking objects. No more striking instance of this can be found than that furnished by the story of the Jelly-fish. Most, if not all, of my readers have met with this creature, either in the shape of a lifeless lump of clear jelly lying on the sand by the sea-shore, or gracefully swimming in the summer sea, a thing of beauty indeed, yet not to be treated too familiarly. If it could but speak, what a strange tale it would have to tell! But Nature has imposed silence on most of her children, which is after all a good thing for us, for this very silence makes us anxious to discover for ourselves the wondrous lessons which she has to teach, whereby we learn that these humbler creatures, like ourselves, find the world a stern reality, to be faced bravely: and the sooner we realise this the better and more useful lives we ourselves shall lead.

But to our story. You must allow me to tell this in my own way, which I shall do by asking you to go to the nearest pond, get a bottle full of water and weeds, and stand it in the light for an hour or so. Then look carefully on the side of the bottle next the light for some tiny little creatures about half an inch long, with slender stalked bodies, attached by one end to the glass, and provided at the other by long, very delicate, slowly-moving arms: you must seek, in short, for a creature such as that shown in the picture as if seen under the microscope, sticking to a piece of weed (fig. 2). At the top end of the stalk is the mouth, and if you watch carefully you may be fortunate enough to see the long arms catch a water-flea, and carry it towards the mouth. This creature is known as the hydra. In some cases you will see two or even three of these creatures all attached to the same stalk, and if you watch every day, you will at last find that sooner or later this partnership is dissolved, so that the branched hydra has split up into a number of separate individuals—just as many as there were branches.

Now, the fresh-water hydra has some very near relatives which live in the sea, and these fashion their lives on very different lines. In the first place, they, like the hydra, start as single individuals, but sooner or later develop little buds which grow out into arm-bearing creatures exactly like themselves; but these, instead of breaking off as in the hydra, remain fixed and themselves produce branches, which again branch, and so on, until, as you will readily see, in a very short time a colony of animals is produced which bears a remarkable resemblance to a little tree! Such for example as you will see in fig. 4, growing upside down!

You will have noticed that the fresh-water hydra had a wonderfully elastic body, so that when frightened, as by a tap on the bottle, it suddenly pulls itself down into a mere speck of jelly (fig. 2). This feat its sea-dwelling cousins cannot perform, since, frail as they are, some support became necessary when they took to the tree-like habit of growth, and this support is found by encasing the whole body and its branches in an outer coat of a horny, transparent character, with a hole at the top of each branch expanded to form a cup to guard the long arms. So then, when alarmed, all they can do is to draw down the arms into the cup. In the illustration (fig. 5) you will see a branch of one of these colonies as it appears when highly magnified. Some of the animals you will note are fully expanded, while others have partly withdrawn themselves into their cups, which are here very small, though in some species they are quite large. A little closer study of this magnified portion of a branch will show you, here and there, little bud-like bodies like unopened flower buds, attached by a short stalk. One of these you will notice is more developed, and resembles a tree ('jelly-fish,' in fig. 5). If you could only watch it in the living colony you would find that one fine day it broke off from its stalk, and sailed away—jelly-fish, such as you see in fig. 3.

Probably all of you have found the empty shells of these wonderful animal-trees dozens and dozens of times on the beach, and many of you will find them in your collections of sea-weeds brought home as treasures to remind you of the summer holidays. The so-called sea-fir is all that is left of such a colony: the little tree-like tufts which you doubtless found attached to rocks and stones represent other forms. Of course, some of your sea-weeds are really what they appear to be—that is to say, they are true plants; but those of which I speak now, though they have a superficial resemblance to plants, are really animals. In fig. 1 you will see some of the commoner forms of these strange animals as they appear in life.

These colonies furnish us with an interesting illustration of the division of labour, for, as you see, they are formed of two very distinct kinds of individuals. The most numerous of these, those with the long arms, have to capture and digest the food for the whole community, including the little buds and bell-like individuals, for they are mouthless. Their life of work begins, however, after they blossom into jelly-fish, and they have a very important duty to perform. With the great wide sea for a playground, they wander for a time at will, warmed by the glorious sun, feeding on the delicious meats to be found at the surface, for which their humble sisters at home must stretch their arms in vain. And so they wander, far from the place which gave them birth, growing bigger and stronger, finally fulfilling the task which they were sent out to perform—the production of eggs from which new colonies are to be started. These eggs grow into a little slipper-shaped creature which swims by means of the rapid waving motion of hair-like elastic rods which cover the whole body. At last, tired out, it settles down, grows into an animal resembling its cousins of the fresh water, and then starts branching out to form a colony like that from which it started.

This device of fixed and stay-at-home workers and wandering egg-layers is of the greatest use to the species, as a little reflection will show. If the eggs dropped to the ground and hatched all around the parent colony the neighbourhood would soon become like some human cities—overcrowded, and overcrowding means starvation and disease; but by sending off individuals specially charged with the founding of new colonies on new territory, all these troubles are avoided.

W. P. Pycraft, F.Z.S., A.L.S.