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Page:Popular Science Monthly Volume 21.djvu/774

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THE POPULAR SCIENCE MONTHLY.

mated "mimicry." That cuttle-fishes possess such a power is well known. The hue of an octopus may so closely resemble that of the rock to which it attaches itself, that the observer can with difficulty say which is rock and which is animal. A flounder's color is in the same way assimilated to the sand on which it rests, although in the fish the alteration of color seen in the cuttle-fishes is not represented.

The manner of production of the changes of hue and play of "shot" colors in the cuttle-fishes is really analogous to that whereby the famed chameleons effect their alterations of hue.

The locomotion of the cuttle-fishes forms a point of interest in connection with their general structure and physiology. Any one who has attentively watched the movements of an octopus in its tank must have been struck by the literally acrobatic ease with which it accommodated itself to the exigencies of its life and surroundings. In their lithe, muscular, and flexible arms, the cuttle-fishes possess an apparatus which is equally serviceable for the capture of prey, and for walking mouth downward—that is, in their structurally natural position. They possess, likewise, the power of swimming upper side forward—or popularly stated "backward"—by means of the jets of water which, by forcible contractions of the muscular mantle-sac, are projected from the tube or "funnel" situated on the hinder face of the body. These jets d'eau consist of the effete water which has been used in breathing, so that the act of expiration and the effete water of respiration together become utilized, in the economical wisdom of nature, as a means of propulsion. The mysterious backward flight of an octopus through its tank (Fig. 1), when, detaching itself from its hold on the rock, it swims gracefully and swiftly through the water, is effected in the manner just described. This form of hydraulic apparatus, imitated in experiments in marine engineering, serves but to strengthen the wise man's adage concerning the utter lack of novelty in terrestrial and mundane things.

It is equally interesting to note that some of the squids or loligos—named popularly "flying squids"—appear to be able to rise from the surface of the sea and to spring into the air after the fashion of the flying-fishes. Instances are mentioned of the flying squids having occasionally landed themselves on the decks of ships in their atmospheric leaps.

The "arms" or "feet" demand, however, a somewhat detailed mention, on account of their armature. In all cuttle-fishes, save the exceptional pearly nautilus, the arms are either eight or ten in number, and are provided with acetabula, or "suckers." Those cuttles in which ten arms are present and of these the squids and sepias form good examples—have two of these appendages produced beyond the remaining eight in length. The "suckers" (Fig. 2, a), which constitute a most noteworthy armament of the arms, are borne on short