The public of the Aquarium, seeing the flat heads of the swimming animals near the glass, would scream and wave their arms as though they could be seen by the fishy eyes of stupid fixity.  Then they would experience a certain dismay upon perceiving that the fish continued their course with indifference.

Ferragut smiled before this deception.  The crystal that separated the water from the atmosphere had the density of millions of leagues,—­an insuperable obstacle interposed between two worlds that do not know each other.

The sailor recalled the imperfect vision of the ocean inhabitants.  In spite of their bulging and movable eyes that enable them to see before and behind them, their visual power extends but a short distance.  The splendors with which Nature clothes the butterfly cannot be appreciated by them.  Absolutely color-blind, they can appreciate only the difference between light and darkness.

Complete silence accompanies their incomplete vision.  All the aquatic animals are deaf, or rather they completely lack the organs of hearing, because they are unnecessary to them.  Atmospheric agitations, thunder-bolts and hurricanes do not penetrate the water.  Only the cracking shell of certain crabs and the dolorous moaning near the surface of certain fishes, called snorers, alter this silence.

Since the ocean lacks acoustic waves, their inhabitants have never needed to form the organs that transform them into sound.  They feel impetuously the primal necessities of animal life,—­hunger and love.  They suffer madly the cruelty of sickness and pain; among themselves they fight to the death for a meal or a mate.  But all in absolute silence, without the howl of triumph or agony with which terrestrial animals accompany the same manifestations of their existence.

Their principal sense is that of smell, as is that of sight in the bird.  In the twilight world of the ocean, streaked with phosphorescent and deceptive splendors, the big fish trust only to their sense of smell and at times to that of touch.

Sometimes buried in the mud, they will ascend hundreds of yards, attracted by the odor of the fish that are swimming on the surface.  This prodigious faculty renders useless, in part, the colors in which the timid species clothe themselves in order to confound themselves with lights or shadows.  The greatest flesh-eaters see badly, but they scrape the bottom with a divining touch and scent their prey at astonishing distances.

Only the Mediterranean fishes, especially those of the Gulf of Naples, were living in the tanks of this Aquarium.  Some were lacking,—­the dolphin, of nervous movement, and the tunny, so impetuous in its career.  The captain smiled upon thinking of the mischievous pranks of these ungovernable guests whose presence had been declined.

The voracious shark (cabeza de olla), the persecuting wolf of the Mediterranean herds, was not here either.  In his place were swimming other animals of the same species, whitish and long, with great fins, with eyes always open for lack of movable eyelids, and a mouth split like a half-moon, under the head at the beginning of the stomach.