William Keith Brooks

A Remarkable Life History and Its Meaning

XAVIGATORS in tropical seas often speak of sailing for days through regions where the water of the ocean, to a depth of many feet, is filled with small transparent animals, which are attached to each other in such a way as to form chains or trains like trains of cars. Although these animals are perfectly transparent and jelly-like in appearance, the fact that their bodies are of sufficient consistency to admit of their being somewhat roughly handled, or even removed from the water, without essentially changing their shape, at once distinguishes them from such animals as jelly-fishes; and a very superficial examination is enough to show that they are quite different from these in organization. They belong to the group Tunicata, animals which have been classed with the Mollusca, although we now know that the resemblances which formerly led naturalists to this idea of their affinity are merely superficial, and without scientific value. Most of the Tunicata are, in their adult state, attached to heavy bodies which rest upon the bottom of the ocean; stones and shells, for instance. A few, however, are locomotive and are to be met with swimming at the surface; most of the latter belong to the genus Salpa, and to these we will at present confine our attention. Although the Salpme are most often met with in the warmer parts of the ocean, they are by-no means confined to the tropics, but have been found south of the most southern point of Australia, and north of Scotland and Norway. They are abundant only after the water has been for some time undisturbed by winds, and as calms are more frequent within the