CHAPTER III. PORIFERA (Sponges). WHAT is an animal? Nothing seems easier than to answer this question. Our thoughts in a moment recall the image of the stately horse shaking his neck of thunder, and projecting columns of vapour through his translucent nostrils; or the painted tiger crouching in the jungle, awaiting in lithe readiness the approach of some unconscious antelope to make his mortal spring; or the trembling antelope itself, as it pants, and struggles, and groans beneath the fangs of its merciless foe. Nothing appears simpler than to define an animal. A being with head, and body, and limbs; full of energy and vigour; possessed of various instincts; master of many ingenious contrivances all helpful to its peculiar economy; executing various movements; manifesting intelligence in different degrees, and governed by a wayward will. True, such a creature as this is an animal; but are there no animals but such as possess these characteristics? Let us enumerate a few familiar instances. Look at the ferocious crocodile. Is this an animal? "Without doubt,” you answer. The serpent, the frog, the mackerel ? "Without doubt," you still reply. The worm, the caterpillar, the snail, the oyster ? "Yes," you say still, perhaps hesitating a little upon the last, as its energy and vivacity are confessedly not great. Still, probably, you have been accustomed to consider an oyster as an animal, though one in which the animal life is in about its lowest condition; and you think you have got through your catechism without any great difficulty. Stay: we must ask you to descend with us a step or two lower than the oyster. You have, perhaps, seen on the sandy shore in summer the flat cakes of motionless, colourless jelly, commonly called sea-blubber are these animals? If you have seen them in the sea, possibly you will consider the spasmodic contraction of the circular disk at regular periods as an indication of life, though you begin to see that in such a mass of clear jelly as this, without limbs, without organs, without senses, without intelligence, without a power of governing its movements, we have departed somewhat considerably from such a standard of animal nature as the horse or the tiger presented. : But let us look further yet. The brilliant-hued Sea Anemone that adheres to the rock, and expands its lovely fringed disk like the blossom of a flower,-what is this? People call it an animal-flower; but what is it, animal or flower? Probably you are at last puzzled; you are inclined to think it a sort of marine flower, though its fleshy substance, and its shrinking when touched, produce some misgivings in your decision. Well, try again. In the baskets of dried sea-weed which are exposed for sale in watering-places, you have often seen the papery leaves of pale-brown hue, or feathery plumes of pure white, mingled with the crimson and green specimens. You have never doubted that these are all sea-weeds, that is plants, alike. And yet if you saw these growing on their native rocks, plant-like as they are in form, you might discern, on careful examination with a pocket lens, that from various points of their surface tiny star-like circles of radiating points were protruding, that possessed spontaneous motions, and exhibited a shrinking sensitiveness to danger, and a power of seizing and swallowing food; and you would suspend, if not alter, your judgment. If now, we ask, What is an animal? you will confess that the answer is not so easy as it appeared at first; still there remain some characters common to all the beings that we have glanced at, and these we may perhaps conclude to be inseparable from, and distinctive of, animal existence. Of these characters, the most constant and the best defined are the power of spontaneous motion, and the possession of a stomach, or at least an enclosed cavity, in which other substances are converted into nutriment. With regard to the former of these characters, what shall we say to the Sensitive plants of the tropics, the pinnate leaflets of which fold together, and the jointed leaf-ribs fall, on the rude touch of a foreign body? What to the plant called Venus' Fly-trap (Dionaea muscipula), found in the marshes of North America, whose broad two-lobed leaves, armed with strong teeth standing up from the surface, ordinarily lie widely expanded; but when an insect touches their hairy centres, instantly fly up like a rat-gin, the teeth cross each other, and the offending fly is pierced, and held a prisoner until it dies? What to the Gorachand of Bengal (Hedysarum gyrans), whose |