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Page:Popular Science Monthly Volume 56.djvu/492

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478
POPULAR SCIENCE MONTHLY.

water, their axes making various angles with the horizontal, their pectorals folded to their sides. When swimming slowly it is chiefly by the use of the pectorals. The strokes of the pectoral are lazily given, and the fish glides on after a stroke till its impetus is exhausted, when another stroke is delivered. The fishes frequently

PSM V56 D0492 Ipnops murrayi and chlorophtalmus gracilis from the nz deep.png
Fig. 4.Ipnops Murrayi, living at a depth of 1,500 to 2,100 fathoms.
Fig. 5.Cholorophthalmus gracilis, from 1,100 fathoms, off New Zealand.

roll slightly from side to side at the exhaustion of the result of a stroke. When swimming rapidly the pectorals are folded to the sides, and their locomotion is then similar to that of a salamander—by the motion of the tail. They readily adjust themselves to different depths, and are usually perfect philosophers, quiet, dignified, unconcerned, and imperturbed, entirely different from such eyed species as minnows and sunfishes which are sometimes found in caves and which are much more readily disturbed by any motion in the water, making it almost impossible to capture them when found in the caves. The pectorals are also almost exclusively used when quietly rising in the water. At such times the pectorals are extended laterally and then pressed to the sides, beginning with the upper rays. A downward stroke is delivered in this way not quickly, but with apparent lazy deliberation. In swimming the pectorals are brought forward upper edge foremost. The center of gravity seems to be so placed in regard to their various axes that the fish does not lose its balance whatever its position. They float horizontally in the water without any apparent effort to maintain their position, or with the main axis inclined upward, with the snout sometimes touching the surface of the water, apparently lifeless. Once one was seen resting on its tail in a nearly vertical position, and one while quietly swimming was once seen to leisurely turn a somersault and swim on undisturbed. At another time the same individual rolled completely over. When one of them is kept out of the water for a short time it frequently goes in a corkscrew-shaped path through the water, continually spinning around its long axis. In their quiet, floating position it is difficult to determine whether they are alive or not.