there are some that are instructed to form associations, which yet are not united by any material tie or common body, so as to be physically inseparable. Of this description are the Salpes,1 or biphores, as the French call them. These are phosphoric animals, so transparent that all their internal organs and all their movements, and even all the contents of their intestines, may be distinctly seen. They are gelatinous like the medusas and beroes, and like them dissolve into water. Their organization, however, proves them to be Tunicaries. Certain species of these animals, in this respect unlike every other genus of the animal kingdom, have the property of uniting themselves together, not fortuitously and irregularly, but from their birth and in a certain undeviating order. Bosc observed the reunion of the confederate Salpe, which he thus describes: "Every individual is attached by its sides to two others, the mouth of which is turned to the same side; and by the back also to two others, when it is turned to the opposite side." In this circumstance it presents an analogy to the combs of the hive bee, in which each comb consists of a double set of cells placed base to base, with the mouths of each set looking opposite ways, and the cells so placed that a third of the base of three cells occupies the whole of one

1 Salpa.

2

2 Salpa confœderata.

base in the opposite set. This reunion, in the salpes, is effected by means of eight pedicles, of a nature exactly similar to that of the body. It is perfectly regular, that is to say-all the individuals are at the same distance and height, all the heads in one row are turned to the same side, and those of another to the opposite. These rows usually consist of from forty to fifty individuals, and are carried by the waves sometimes in a straight, sometimes in a curved, and sometimes in a spiral line. In the sea, during the day, they appear like white ribands, and during the night like ribands of fire, which alternately roll up and unroll, wholly or partially, either from the motion of the water, or from the will of the animals that compose them. They are found in the ocean only at a great distance from land. Professor Eschscholz mentions one, intermediate between the Salpes and Pyrosomes-and a similar one is now in the Hunterian Museum3which by means of a pedicle appeared to be attached to some common body, all of them arranged in rows with the head turned to the same side; Savigny, whose eye nothing escaped, and the acumen of whose intellect equalled that of his sight, alas now dark, further informs us, that the Salpes adhere to each other only by certain gelatinous protuberances, or as Lamarck sus

PLATE XI. FIG. 3.

3 PLATE IV. FIG. 2.

2 Anchinia.

pects, certain lateral suckers, disposed so as not to impede the motions of the muscles; but their union is only temporary. At a certain age, M. Peron observes, these animals separate, all the large individuals being solitary. The same traveller is of opinion that the concatenation of the Salpes is coeval with their birth.

The object of Divine Providence in endowing these animals with an instinct so singular can only be conjectured. They are of so very frail a nature, that perhaps when first produced, the fluctuations of the mass of waters, to the surface of which they appear to rise, might be sufficient to destroy them, or to carry them to the shore, where they would inevitably perish; but by being united in bands, they may be better able to resist their force, and perhaps the more vivid light they thus produce, may be designed for defence,1 or to answer some other important purpose. When they have attained maturity of size and strength they may be better able to direct their course and avoid these injuries. The young of terrestrial animals generally are associated, under the guidance and protection indeed of the mother, till they are of age to take care of themselves. The object of Providence in both cases is the same, though the modes of its accomplishment vary according to the situation and circumstances

See above, p 178.

of individuals. When we see such paternal care manifested for the welfare and maintenance in existence, of beings so frail, that a mere touch would dissipate them, we cannot but assent to the observation of the Psalmist, that "His tender mercies are over all his works,' the least and most insignificant as well as those that appear to occupy the most elevated place in the animal kingdom: and we may feel a comfortable assurance, built on this ground, that the eye which regards even these seemingly insignificant creatures, will, if we cast not off our confidence, never overlook us, or be indifferent to our welfare.

The last and highest tribe, belonging to the present class, are those which are never united to each other, but are solitary in all stages of their existence. These, as well as the preceding ones, make a near approach to the real Molluscans, at least their external and internal envelope bears considerable analogy with that of bivalve shells, as Lamarck acknowledges, though they differ in having a distinct organization, the shells of bivalves having neither apparent vessels nor fluids, while, in these Tunicaries, the covering, both external and internal, in some species, exhibits vascular ramifications very conspicuously.

Though several of the animals belonging to

the class of Tunicaries are interesting on account of their singularity and beauty, I shall only select two, one from the aggregated, and one from those that are simple, for description and further remarks, and then proceed to the great class of Molluscans. Who would think, asks Lamarck, that the Pyrosome, first observed by Peron and Le Sueur, was an assemblage of little aggregate animals; any one that looked at this animal, or at Savigny's figure of it,' would mistake it for a simple polype, with a number of leaf-like appendages growing from its skin: but a closer examination would give him a very different idea, and he would discover, with wonder, that it was a mass filled with animals, united by their base, exceeding the number of the above appendages. The common body that contains these creatures resembles a hollow cylinder closed at its upper extremity and open at the lower; this body or mass is gelatinous and transparent, a number of tubercles of a firmer substance than the tube, but at the same time transparent, polished, and shining, differing in size, cover the surface; some being very short, and others longer, and the longer ones terminated by a lance-shaped leaflet. At the summit of each tubercle is a circular aperture, without tentacles, opposite to which is another circular orifice which is toothed.

The pyrosomes are the largest of the phosphoric

Anim. sans. Vertèbr. PL. IV. FIG. 7.