« ForrigeFortsæt »
it always contains a multitude of animalcules and very minute plants, which the fishes are continually swallowing.”
When Creative Wisdom covered the earth with plants, and peopled it with animals, he laid the foundations of the vegetable and animal kingdoms with such as were most easily convertible into nutriment for the tribes immediately above them. The first plants and the first animals are scarcely more than animated molecules,' and appear analogues of each other ; and those above them in each kingdom represent jointed fibrils.
It is singular and worthy of notice, that the Creator after the creation of inanimate matter, probably first imparted the living principle to bodies of the same form with the molecules and fibrils into which that matter is resolvable, thus uniting, by common characters, things essentially distinct, and preserving unbroken that wonderful chain which links together all created things.
Every body, who has eyes, is aware, that vegetation takes place upon almost every substance, upon the bark of trees, upon naked rocks, upon brick walls and tiled roofs, and even upon glass when not constantly cleaned. The first plants, that take on these their station, usually look like green or yellow powder, when they decay forming a little soil, in which others more conspicuous find sufficient nutriment, and so one succeeds another till a sufficient portion of soil
1 For instance, Globulina and Monas. 2 Oscillatoria and Vibrio. See Appendix, note 21.
a covers the rock, &c. to afford the means of life and growth to more perfect plants, and often to arborescent ones. An analogous process takes place in the water. The matière verte of French authors makes its appearance, and other Hydrophytes, in conjunction with the Infusories, form as it were a first soil for the support and maintenance of animal life, both for those which derive their nutriment from vegetables, and those that feed on beings of their own class. Thus a maintenance is provided for higher forms, and, at last, for the highest ; and a table is spread, both on the earth and in the waters, for every living thing, from that which the eye cannot discover, to man, the head and king of all.
How wonderful and adorable is that Almighty Being, who thus made all things dependant upon each other, and based the visible world, in the three great departments into which we see it divided, upon an invisible basis, and in which cohesion and life are maintained by those powers which God has placed as rulers in the physical world, and by which he still acts upon the universe of existences.
Functions and Instincts. Polypes.
The tribe of animals to which we are next to direct our attention, though not invisible like the last, are almost equally concealed from our view by the medium that they inhabit; so that, with the exception of those that abound in fresh water, and are easily kept alive for examination, the great body of them inhabiting the ocean, can seldom be studied in a living state. All the polypes are aggregate animals, in which they differ from the majority of the preceding class. The most imperfect of them, as the sponges and some of the alcyons, seem to consist merely of a gelatinous mass, without any organs of préhension, which by its alternate contraction and dilatation, imbibes or sends out the water from which the animal derives its nutriment; but the great majority have a mouth furnished with arms or tentacles varying in number. These are described as tubes, filled with fluid, expanding at the base into a small cavity, which when contracted necessarily propels the fluid into the tentacles, and thus extends them; but when
the tube contracts, the fluid flows back into the cavity, and the points of the tentacles converge over the mouth.
These parts are not only organs of sense, but also serve many other purposes, particularly those of prehension and motion; and they very probably assist in respiration, which appears evidently connected with the alternate contraction and expansion of these animals. They are also so constructed as to lay hold of every substance that floats within their reach, whether by means of any gummy excretion like bird-lime, as some suppose, or whether they are furnished with very minute suckers by which they can adhere to any substance, has not been ascertained. Trembley observed, that when the common polype of fresh water touched any little animal with one of its long tentacular arms, it was immediately arrested, and in spite of the most violent efforts to liberate itself, which he compares to those of a fish that had been hooked, was held fast, and carried to the mouth of the polype and swallowed.
The body of polypes is formed of a kind of inspissated mucus, with confusedly agglomerated, and probably nervous, molecules equally distributed; it is covered by no skin, is extremely contractile, and forms an alimentary sac open at one end, serving both for mouth and anal passage. The equal distribution of nervous molecules through the whole substance of these animals, will account for their extreme tenacity of life. In fact, this uniform gelatinous mass, which is without any organized structure, may be regarded as a kind of primary substance, which possesses characters, in some respects, common to both animal and vegetable matter.
This substance without any nervous centre --though nervous influence, one would think must be in most force round the orifice where the tentacles are in action,-yet full of cerebral matter, sensible to the light without any organ of sight; extremely irritable; alternately contracting and expanding, and thus moving without any apparatus of muscles; with no trace of organization but the tubular rays that surround its mouth, which appear to perform the office of eyes, hands, feet, and lungs; this singular substance lends a clue to form the class into Orders according to the circumstances in which it is placed.
1. In the common Polypes of our ditches and stagnant waters, it is a naked branching elementary sac or canal, without any internal support, and endued with powers of locomotion.
2. In the Madrepores and others, its Maker for mighty purposes has enabled the animal to form for itself a fixed calcareous house or polypary
1 Hydra viridis, fusca, &c.