Page:Popular Science Monthly Volume 11.djvu/200

188 from side to side, and tapering to a fine extremity. In the smallest gars it was longer than the fin below, in the older it was shorter, while in the adults no trace of it appears.

These two tails have very different movements. The lower, corresponding to the caudal fin of the ordinary fish, is used in three ways. When the little gar is in a gentle current, and wishes not to be carried downward, the fin is made to execute a series of undulatory movements, such as have been described by Prof. Agassiz respecting the dorsal fins of young pipe-fishes, etc., and such as the writer has observed with the long dorsal fin of Amia.

This tail is also strongly flexed to one side, as with ordinary fishes, in order to change the course. And it is rapidly moved from side to side for all sudden and rapid locomotion, as when frightened.

The movements of the filament were first described by Prof. Agassiz, and he called attention to them upon several occasions. But his descriptions are very brief, and, upon one point, seem to require modification.

The filament is in almost constant vibration. Occasionally, when the gar is at rest, and perhaps also when it is turning, or rapidly swimming, the filament is not used. But usually the vibrations are so rapid that the tip of the filament is invisible, excepting as an indistinct blur. Generally, it is directed backward and slightly upward, but at times it is bent to one side, or elevated to nearly a right angle with the body, the tip all the while in constant vibration. Those who have watched the tail of an irritated rattlesnake, or even of a common striped snake, under strong excitement, may form a pretty correct idea of the nature of this movement. It was characterized by Prof. Agassiz as "involuntary;" and so it may be regarded, since its rapidity is such as to preclude the idea of a separate volition for each movement. But the gar, evidently, has entire control of the vibrations; for they are more or less rapid at different times, and are occasionally intermitted; the position of the whole filament is changed at will; finally, the muscular bands upon each side of the cartilaginous rod, which runs through the filament, consist of the striped variety of muscular fibre, as are the other voluntary muscles.

This is all the writer has seen of living young gar-pikes. But the explanation of the peculiar double tail is furnished by some still younger specimens, the smallest of which is shown, enlarged, in Fig. 9.

These little gars were scooped out of the Red River, near Shreveport, Louisiana, in the spring of 1871, by a lad only ten years old, who had heard the writer say that he wished for very small fishes. At that point these young gars were then as abundant as minnows, as easy to catch, and commercially as worthless. All of them are less than two inches long, and among them are two about three-fourths of an inch in length. These last are not only much smaller than any