Page:Popular Science Monthly Volume 46.djvu/847

Rh abide in the shallows. Inasmuch, however, as the young shad possess the continuous dorsal fin along the body incident to the earliest and lowest fishes, the so-called instinct is most likely a reversion to the ancestral habit, such forms being characteristic of deep waters.

Their burden laid down, their object accomplished, the parent fish, worn with privation and spent with effort, turn at last seaward. Emaciated and exhausted, they have become worthless to the fisherman, who frequently observes them dead or apparently dying, drifting down the stream. It is likely, however, that they recuperate rapidly upon reaching the sea, having then access to their customary food, and, if escaping marine carnivora and surviving until the following spring, they renew their arduous voyage, stronger and larger fish, once more to strenuously strive and suffer, but not probably again to return. For the mass of our migratory fish may be likened to some of our familiar wayside plants, that devote their vital energies to the fructification of their seed: with its ripening they wither, with its complete formation they die.

Of the voided eggs, but a very small fraction develop, many are unfertilized, many are devoured by various depredators, many perish by changes in temperature, by floods, or by disturbances of the place of deposit. Of the scanty remnant that become fry, there again results a trifling fraction that mature; many fall victims to innumerable enemies, to lack of sustenance, and to other fatalities. Surviving all these, the young shad in a few months descends the river; then, quitting the fresh water that has nurtured and sustained it, launches boldly out for its distant and unknown home in the obscurity of the great salt sea. Still in its new and strange element does it run the gantlet of danger and death, but instinct guides it to its ancestral abode, whence two or three years later it emerges one of a host of adult fish burdened with a sense of unaccomplished parentage.

Leaving their home in the far deep, the shad, in beginning their annual pilgrimage, rise to the surface and then direct their course landward, the earliest migrants being those in which the propagative function is most advanced. Pursuing their way over the comparative shallows that widely fringe our continent, and joined by other communities bent upon the same devoted errand, they gather in our estuaries and about the mouths of our rivers, and there they linger until the effluent waters are warmer than those of the sea. With the manifestation of this sign the waiting multitude, freighted with a dawning generation that engages their overmastering solicitude, form into rank and column, and with a common impulse set out to conclude their mission of selfimmolation and sacrifice for the maintenance of their race.