Page:Popular Science Monthly Volume 3.djvu/547

Rh In a word, what is the function of this lash in each of these cells, which, combined, and taken with the skeleton, constitute a sponge? Let us try to see. If we take a morsel of a toilet-sponge, and put it under a microscope of moderate power, we find that it is made up of a mass of complicated net-work. There is more or less regularity in the meshes; and these are found of various patterns in the different species. This heap or mass of net-work, commonly called a sponge, is really the skeleton of the sponge. When living it is covered with, or literally embedded in, a glairy, gelatinous, or albuminous substance. But this is so unlike ordinary animal tissue—for it seems, really, tissue-less—that it has received the technical name sarcode. This sarcode fills the meshes above mentioned; and is held in place by innumerable tiny spicules, mixed in, so to speak, like the hair in the mortar of the plasterer. So little consistency has this sarcode, or sponge-flesh, that but for this natural felting it would dissolve and flow away. Now, take an ordinary sponge into the hand. We observe several large apertures, at or toward the top. These are called the oscula. They are the exhalant vents of the entire system. At these openings is expelled, with some force, the water that has been taken into the living mass, and deprived of its nourishment. But how is the water brought in through that glairy sarcode? Besides the oscula, which are few, and readily seen, even in the skeleton, there are innumerable tiny inlets known as pores. These are not visible in the skeleton, as they really belong to the sponge-flesh. These pores open into the meshes, and enter directly certain little cavities, or chambers, that stand connected with circuitous passages, which finally lead to the large outlets, or oscula. The pores are very small, and yet, compared with the cells, are very large. The little chamber into which the pore opens has its walls built up with these uniciliated cells. Now, if we could only peep into the privacy of that chamber, with its walls of living stones, without making any disturbance, we should find every cell lashing its cilium with great vigor, and all in such harmony of accord, that it would seem like

The beating of each lash is doubtless downward, that is, inward; the effect of which is, a vacuum above, into which the water presses through the external pore. A second result of this downward beating of the cilia from a myriad of cells is, the impulsion of the passing water through the ramifications leading to the oscula. Thus the running of the waters is the sponge's ancient "Runic rhyme." Every sponge, then, has a very complete aquiferous system: its conduits at, the entrance of and along which the busy one-lashed cells occupy themselves forcing the water along; and the oscula, which may be likened to the outlets of sewers. During this circulation of the fluid