Physalia, the Portuguese man-of-war, with its beautiful blue float, may at times be seen on all sides. The float, filled with air, serves to keep the animal on the surface, and, driven by the wind, to bear it from place to place. It is a curious animal, or rather cluster of animals we should say, for naturalists now consider it to be a group of individuals, having different functions, but working for the same general cause—that of supporting the mass. They say that in this group there are some whose sole purpose is to obtain food, some to digest, others to reproduce, etc., yet each is an individual animal working for the good of the whole, that Fig. 6.—Portuguese Man-of-War (Physalia arethusa). the whole may work for its good, and that in conjunction they may perform all the functions of life necessary to the well-being and general welfare of the whole united colony. The cluster has most remarkable defensive powers, being well furnished with lasso cells or stinging organs. These consist of little barbed, arrow-like points, fastened to thread-like arms, each of which is coiled up in a little cell. Whenever it is necessary to use them they are hurled out with violence, and each barb, striking the object, penetrates, for it has the power of "working into" flesh, and, being covered with a sort of poison, it in conjunction with many others benumbs the prey and renders it harmless. That the Physalia possesses this property to a marked degree, some of the sailors of the Albatross can testify, for they incautiously placed their hands in a tub of water containing one, and the shock they received was compared in violence to a strong shock from a Leyden jar. Sea-anemones possess this same property, although the common shore species can affect only very tender animals. I have seen a deep-sea anemone, six inches in length, by this means kill and afterward swallow a lively fish a foot long, that was placed in the aquarium with it. The fish barely touched the anemone, then seemed incapable of moving farther, and after a few struggles became paralyzed. These arrow-points possess the power of motion for several hours after being detached from the animal. Lasso cells can be replaced when lost, and in a very short time. On a square foot there are millions of cells. It is a curious fact that all well-defended animals
Page:Popular Science Monthly Volume 35.djvu/678
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THE POPULAR SCIENCE MONTHLY.