At certain seasons, eggs are produced within the body of the parent in appropriate ovaries, where they are retained for a time. They are then transferred to a kind of marsupial pouch, analogous to that of the kangaroo, where their development proceeds. After passing through certain changes here, the egg issues from the maternal pouch as an oval body, clothed with cilia—an animalcule in external aspect, and as unlike its parent as can well be imagined. For awhile the little creature dances freely through the water, and leads a gay, roving life; but at last it prepares to 'settle;' selects a fitting locality; applies one extremity of its body to the surface of stone or weed, and becomes attached. And now another change passes over it. The cilia, no longer needed, disappear. A mouth is developed at the upper extremity of the body, furnished with a number of arms. Gradually this number increases, and the jelly-fish now appears in the disguise of a polype, which feeds voraciously on the members of the class from which it has itself so lately emerged. At this point there is a halt. The medusa remains in its polype state for some months. At the expiration of this term, a strange alteration in its appearance begins to take place. Rings are formed round its body, from ten to fifteen in number. These gradually deepen, until at length it is literally cut up into a number of segments, which rest one upon the other—their upper margins becoming elevated, and divided into eight lobes. It is, in fact, a pile of cup-shaped pieces, very loosely connected together. A little later, these pieces free themselves successively, and the sedate polype disappears in a company of sprightly young medusæ. These beings, indeed, still differ in some respects from the adult animal; but the differences gradually vanish, and we have the perfect jelly-fish as the final result of this extraordinary series of transformations.
Similar observations have been made respecting other tribes amongst the lower animals, and some interesting generalisations have been founded upon them, into which, however, it is not our present purpose to enter.
The Acalephæ are the principal agents concerned in the production of the beautiful phenomena of phosphorescence. The minute species—mere gelatinous specks—swarm at times by countless myriads in the waters of the ocean, and make its surface glow with 'vitalised fire.' The waves, as they curl and break, sparkle and flash forth light, and the track of the moving ship is marked by a lustrous line. 'In the torrid zones between the tropics,' says Humboldt, 'the ocean simultaneously develops light over a space of many thousand square miles. Here the magical effect of light is owing to the forces of organic nature. Foaming with light, the eddying waves flash in phosphorent sparks over the wide expanse of waters, where every scintillation is the vital manifestation of an invisible animal world.' Beneath the surface larger forms are seen, brilliantly illuminated, and lighting up the mystic depths of the sea. Fiery balls and flaming ribbons shoot past; and submarine moons shine with a soft and steady light amidst the crowds of meteors. 'While sailing a little south of the Plata on one very dark night,' says Mr Darwin, 'the sea presented a wonderful and most beautiful spectacle. There was a fresh breeze; and every part of the surface, which during the day is seen as foam, now glowed with a pale light. The vessel drove before her bows two billows of liquid phosphorus, and in her wake she was followed by a milky train. As far as the eye reached, the crest of every wave was bright; and the sky above the, horizon, from the reflected glare of these livid flames, was not so utterly obscure as over the vault of the heavens.' Even in our own seas very beautiful displays of phosphorescence may be witnessed. On fine summer nights, a soft, tender light plays round the boat as it moves onward, and the oars drop liquid fire. For how much of beauty are we indebted to these living specks of jelly?
Of the extreme minuteness of some of the species, an idea may be formed from the fact, that 110,000 might be contained in a cubic foot of water. We can say nothing with certainty as to the cause of the phosphorescence of the medusæ, and shall not trouble our readers with mere speculations.
The jelly-fishes furnish us with a striking illustration of the profusion of life in the ocean. Provision has indeed been made for securing in all the realms of our globe the largest possible amount of sentient being, and consequently of happiness. And to each tribe a definite part is assigned—a special mission is intrusted. None can be spared from the economy of nature. The shoals of microscopic medusæ store up in their own tissues the minute portions of nutritious matter diffused through the waters, and supply food for the support of higher organisms. All the tribes of animated beings are dependent one upon another. That the greatest may enjoy its existence and fulfil its work, the least must hold its place and discharge its function. They co-operate unconsciously to secure the unity and harmony of a system which is designed to promote alike the interests of each and all of them.
STEEPLE-JACK'S SECRET.
You want me to tell you how it comes to pass that I am able to glide up a steeple like a spider, get astride upon the cross, and pull off my cap to the crowd below, like a gentleman on horseback saluting his acquaintances.[2] You want me to explain on what principle, as you call it, I do this. Well: principle, I suppose, means the rule or law by which a man does what he ought to do; and if so, it is a very good word to use. I will oblige you by explaining my principle, for I am as affable as any man that creeps to his dying day upon the surface of the earth; and I will tell you how it chanced that I found it out: at least I will try, for I am no scholar; and if you wish to understand me, you must have your ears open, and catch a meaning when you can. And this will do you good, whether you make anything out or not. I know fellows that go to the lectures, and come back as empty as they went. But what of that? They think they understand, and thought breeds thought; and when a man's mind is fairly astir, it is odds but something good turns up.
You must know, then, I began the world as a sailor; and I marvel to this day how I ever became anything else. Sailors are the stupidest set in creation. They are mere animals, except in the gift of speech; good, honest, docile animals, perhaps, but dull and narrow. They go round the small circle of their duties like a blind horse in a mill. Their faculties are rocked by the waves and lulled by the winds; and when they come ashore, they can see and understand nothing for the swimming of their heads. Drink makes them feel as if at sea again; and when the tankard is out, they return on board, and exchange one state of stupefaction for another. Well, I was a sailor, and the dullest of the tribe. No wonder, for I was at it when a young boy. I was never startled by the sights or sounds of the sea. The moaning of the wind, the rush of the waves, the silence of the calm, were parts of my own existence; and in the wildest storm, my mind never took a wider tack than just to think what the poor devils on shore would do now.