symmetry. By means of the high magnifying power which I have now applied, each of these pinnre is seen to he roughened with whorls of knobs, which are accumulations of cnidse, analogous to those which we lately demonstrated in the tentacle of Laomedea.

In the midst of the area surrounded by the petal-like tentacles, a narrow slit opens into the stomach. This organ is a flat sac, resembling an empty pillow-case hanging down in the centre of the column, and open at the lower end. From this end, which does not extend to more than one-sixth of the depth of the cavity, three threads, much twisted and irregularly thickened, spring off at each side, and arch downwards, for a short distance. These are the reproductive organs, which fringe the free edges of as many delicate membranes which run up as perpendicular partitions between the stomach and outer wall, uniting with both, and thus dividing the space surrounding the stomach into chambers open at the bottom. There are eight of these septa (as the partitions are called), but one on each side is destitute of the fringing twisted thread.

The whole surface of the interior—the walls, the stomach, and the septa—is clothed with fine vibratile cilia, by the action of which constant currents are maintained in the water, which bathes every part of the cavity, freely entering at the mouth. We can distinctly trace these ciliary currents hurling along with irregular energy the products of digestion, in the form of translucent granules, especially along the edges of the septa.

Though the substance of the polype is soft and flexible, it contains solid elements. Just below the expansion of the tentacular blossom, we see imbedded in the skin a vast mass of calcareous needle-like bodies called spicula. Individually, these are very minute, and their form is swollen in the middle, and taper at each extremity, the whole roughened with projecting knots. Collectively, they are grouped in regular forms, crowded into dense masses at the foot of each tentacle ; the mass having a threepointed outline, of which the central and largest point runs up into the tentacle.

Towards the lower region of the column, spicula again occur, scattered throughout the skin, and crowded into groups, one on each interseptal space. These spicula are of a very different shape from the upper ones; for they form short thick cylinders, with each end dilated into a star of five or six short branches, which are again starred at their truncate ends.

If we now sacrifice our little Cow's pap to our scientific

SPICULA OF COWS PAP.

curiosity, we shall see something of its internal structure. When removed from the water, the flower-like polypes soon retract. I now cut open the mass lengthwise with a keen knife ; and you see that it is permeated by canals running from the base towards every part of the circumference, dilating here and there to form the cells which protrude and retract the polypes. This is a complete system of water-supply : the surrounding sea-water, entering at the mouths of the several polypes, bathes the whole interior, and conveys oxygen and the products of digestion together to every part of the compound organism. *> A

The fleshy substance which surrounds these canals is of a loose, spongy character, and grates beneath the knife : a circumstance which is owing to the predominance of the calcareous element here, as you will see when I extract a small portion of it, and, laying it on a slip of glass, treat it with caustic potass. The microscope now reveals a large number of spicula, far larger than those we have hitherto observed, and different from either sort in form. These resemble very gnarled branches of oak, with the branchlets broken off close to their origin, leaving ra<™ed and starred ends.

Chapter XIX. Sea-Anemones: their Weapons

A very vast amount of the energy of animal life is spent either in making war, or in resisting or evading it. Offence and defence are sciences which the inferior creatures can in nowise neglect, since all are interested in one or other, and many in both ; and various are the arts and devices, the tricks and stratagems, the instincts and faculties, employed in that earnest strife which never knows a suspension of hostilities. All classes of animals, invertebrate as well as vertebrate, are warriors by profession : the Spider is as carnivorous as the Lion, and more strategic ; and the invisible Brachion is as ruthless and insatiable as either.

An enumeration and description of the different kinds of weapons, by means of which this truceless warfare is carried on, would make a volume : nor would the subject be then exhausted; for, since it enters so largely into the very existence of animal life, the discoveries of advancing science are ever bringing to light new forms and modifications, strange and unexpected contrivances, all calculated to enhance our view of the inexhaustible resources of the Lord God Omnipotent, " Who is wonderful in counsel, and excellent in working."

I am going to bring under your notice this evening some highly curious examples of animal weapons, of which the very existence was until lately altogether unsuspected : yet so profusely distributed that they are eminently characteristic of the animals we have been 2 a 2 recently considering—viz., the Medusae and the Zoophytes. They have repeatedly fallen under our observation in examining the specimens of these creatures which we had selected, but I had reserved the fuller elucidation of them for an occasion in which they should come before us under circumstances of such unusual development as greatly to facilitate our researches. The weapons I speak of are the cnidce or nettling-cells.

Look at thisbeautiful Scarlet-fringedAnemone (Sagartia miniata), expanding to the utmost its disk and tentacles in the clear water of the tank. I touch its body; instantly the blossom-like display is withdrawn: the column closing over it in the form of a hemispherical button, which goes on contracting spasmodically. At the same time see these white threads which shoot out from various points of the surface; new ones appearing at every fresh contraction, and streaming out to a length of several inches, resembling in appearance fine sewing cotton twisted and tangled irregularly.

Now the animal has attained its utmost contraction, and the threads lengthen no more. But already they are disappearing ; each is returning into the body by the orifice at which it issued. It is, as you may see by examining it carefully with a lens, gradually contracting into small irregular coils, at that end which is attached to the animal ; and these little coils are, one after the other, sucked in, as it were, through an imperceptible orifice.

Before the whole have disappeared, we will secure a portion for examination. For this purpose I cut off with sharp scissors about one-sixth of an inch of the extremity of one of the threads, which now I transfer to a drop of sea-water in the compressorium. These threads are called acontia.

Examining this fragment under a low power of the microscope, we readily see that, though at first it seems a solid cylinder, it is really a flat narrow ribbon with the edges curved-in, which can at pleasure be brought into contact, and thus constitute a tube. Like all other internal organs in these animals, its surface is richly ciliated, and the ciliary currents not only hurl along whatever floating atoms chance to approach the surface, but cause the detached fragments themselves to wheel round and round, and to swim away through the water. Though there is not the slightest trace of fibre in the structure of the acontiwni) when examined even with a power of eight hundred diameters, the clear jelly, or sarcode, of which

POEIIOX OF ACONTIUH (flattened). its basis is composed, is endowed with a very evident contractility ; the filament can contract or elongate ; can extend itself in a straight line, or throw its length into spiral curves and contorted coils ; can bring its margins together, or separate them in various degrees ; can perform the one operation at one part, and the other at another, and thus can enlarge or attenuate the general diameter of the cord, apparently at will. Some of these changes can be effected even in the fragment detached

from the animal ; thus proving that the moving power, whatever it is, is situated in the constituent tissue itself.

Under pressure the edges of the flattened acontium appear to be thronged with clear viscous globules, overlapping one another, and protruding ; indicating one or more layers of superficial cells, doubtless forming the epithelium.* As the pressure is increased, these oozr out as long pear-shaped drops, and immediately assume a perfectly globular form, with a highly refractive power. Below these is packed a dense crowd of cnidce, arranged transversely.

Before we proceed to the examination of these curious organs in detail, it may be well to devote a moment's attention to the mechanism by which the acontia themselves, are projected from the body. As this was first described (so far as I am aware) by myself, t I will take the liberty of citing some of my observations on the matter. The omission of the acontia is provided -for by the existence of special orifices, which I term cinclides. The integu- |(v ment of the body, in the Sagartice, is perforated by minute foramina, having a resemblance in appearance to the spiracuht of Insects. They occur in the CINCLIDES. interseptal spaces ; opening a communication between these

The thin, delicate cuticle or skin which covers all the free, uninclosed, internal surfaces of the body.

t In a memoir, entitled "Researches on the Poison Apparatus in the Actiniadtc," read before the Royal Society, Feb. 4th, 1858.

(and therefore the general visceral cavity) and the external water. It follows that they are placed in perpendicular rows ; but I have not been able to trace any other regularity in their arrangement. So far as I have seen, they are so scattered, that one, two, or even more contiguous intersepts may be quite destitute of a cinclis. I would not, however, attach too much weight to this negative evidence, since the animal has the power of closing them individually at will, and that so completely, that the most careful scrutiny does not detect their presence.

Perhaps the best mode of examining them is to put a small specimen of the S. dianthus or>S'. bell is into a narrow parallel-sided glass cell, tilled with sea-water. After a while the animal will be much distended; the exhaustion of the oxygen impelling the Anemone to bathe its organs with as large a quantity of the fluid as it can inhale. The pellucidity of all the integuments will be thus greatly increased. A strong lamp-light being now reflected by means of the mirror through the animal on the stage of the microscope, an inch or a half-inch objectglass will probably reveal the orifices iu question with much distinctness.

The appearance of the cinclides may be compared to that which would be presented by the lids of the human eye, supposing these to be reversed ; the convexity being inwards. Each is an oval depression, with a transverse slit across the middle. When closed, this slit may sometimes be discerned merely as a dark line—the optical expression of the contact of the two edges ; but, when slightly opened, a brilliant line of light allows the passage of the rays from the lamp to the beholder. From this condition the lids may separate in various degrees, until they are retracted to the margin of the oval pit, and the whole orifice is open.

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