192

CHAPTER VI.

Functions and Instincts. Radiaries.

IT happens not seldom to the student of the works of creation, when he is endeavouring to thread the labyrinth of forms in any of the three kingdoms of nature, and has arrived at any given point, to feel doubtful which course to pursue. The road divides, perhaps, into two branches, which both promise to lead him right. At the very outset of the animal kingdom, as we have seen, there was some uncertainty, whether we should begin by the Infusories or Polypes, and now the Tunicaries, or Ascidians as some call them, at the first blush seem more closely connected with the Polypes, than the Radiaries, which Lamarck has placed next to them; but when we consider that the organization is much more advanced in the former than in the latter, not only in the organs of digestion, but in those of sensation, respiration, and circulation, we feel satisfied that the latter, where the object is to ascend, should first be considered. I shall, therefore, now give some account of the Radiaries.

The animals forming this class receive this appellation, because they exhibit a disposition to form rays, both in their internal and external

parts, a disposition which begins to show itself, as we have seen, both in the polypes and the infusories1 with respect to their oral appendages, and is found also in the tunicaries and cephalopods, or cuttle-fish. And this tendency in the works of the Creator to produce or imitate radiation, does not begin in the animal kingdom; the Geologist detects it in the mineral, and the Botanist in the vegetable, for Actinolites, Pyrites, and other substances exhibit it in the former, and a great variety of the blossoms of plants in the latter. We may ascend higher, and say that irradiation is the beginning of all life, from the seed in the earth and the punctum saliens in the egg, to the fœtus in the womb; and still higher in the physical world, sound radiates, light radiates, heat radiates. If we further survey the whole universe, what do we behold but radiating bodies dispersed in every direction. Suns of innumerable systems, shedding their rays upon their attendant planets; and the Great Spiritual Sun of the universe, even God himself, is described in Holy Scripture as that awful Being, "Whose goings forth have been from of old, from everlasting."

Cuvier, and after him several other modern Zoologists, have considered Lamarck's Class of Radiaries as forming a group or class of the

VOL. I.

See above, p. 154, 166, &c.

zoophytes; but when we recollect that they cannot, like the infusories and polypes, be propagated by cuttings and offsetts, this seems to indicate an animal substance in which the nervous molecules are less dispersed, and that some tendency to nervous centres has been established. In the upper classes of invertebrated animals, indeed, many will reproduce an organ when mutilated, and some even a head, but none but the polypes and infusories multiply themselves in the way above stated. It seems, therefore, most advisable to adhere to Lamarck's system, by considering the animals in question, as forming a group by themselves, and to adopt his name of Radiaries.

These are distinguished from the class immediately preceding, the polypes, by being limited as to their growth to a certain standard, as to their form by the general appearance of radiation they usually present, being either divided into rays, as in the star-fish; or having rays exhibited by their crust as in the sea-urchins; or embedded in their substance, forming appendages to their viscera, as in the sea-nettle or jelly-fish. They have not, like the polypes, a terminal mouth or orifice surrounded by food-collecting tentacles ; but one placed, most commonly, underneath their body. Their digestive organs are distinct and more complex. They are never fixed, and are to be met with only in the sea and its estu

aries. Lamarck has divided this class into two orders, the Gelatines' and the Echinoderms.2

1. The Gelatines, which some consider as a distinct class under the name of Acalephes, are distinguished by a gelatinous body, and a soft and transparent skin; they have no retractile tubes issuing from the body; no anal passage; no hard parts in the mouth; and they have no interior cavity, their viscera being imbedded in their gelatinous substance.

Some genera in this Order, like the fishes, are remarkable for an air-vessel which they can fill or empty, and so rise to the surface, or sink to the bottom at their pleasure, but it differs from that of the fishes in being external; others are distinguished by a dorsal crest, which they erect and use as a sail.5

2. The Echinoderms have an opaque, leathery, or crustaceous skin, mostly covered with tubercles, or even moveable spines, and generally pierced with holes, disposed in rows; retractile tubes which respire the water, and are used also for locomotion and prehension, emerge from these holes; a mouth generally situated below, and armed with hard parts; and a cavity simple or divided.

To begin with the Gelatines-in walking upon

1 Radiaires molasses. 2 R. Echinodermes. 3 Acalepha. Physsophora. &c. 5 Vellela.

the sea-shore, I have occasionally remarked an animal of this tribe left by the waves, not much larger than a nutmeg, of a spherical form, with several longitudinal ridges, and nearly as transparent as the purest crystal. If at all injured by the touch, it immediately dissolved. Such delicate creatures has the Creator exposed to the action of the oceanic waves, and they sail gaily on, by means of their ciliated tails, receiving no injury, frail as they are, except in being sometimes cast upon the shore. These lucid gems of the waters,' which abound equally within the polar circle and near the equator, are eminently phosphoric. Bosc says, he has seen millions, which he could scarcely distinguish during the day from the water in which they lived, but which in warm and calm nights afforded the most brilliant spectacle. From their rotatory motion, they seemed then globes of fire which rolled upon the surface of the water. The more rapid their motion, the more intense the light, and their tails always emitted more than their body. They doubtless absorb animalcules with the water that they inspire, and they swim by a motion combining rotation with contraction and dilatation. They are found from a line to six inches in diameter. Providence has destined them to be the food of a vast number of fishes, even the whale does not disdain them; and we may conjecture the havoc that one of these giants

Beroe.