With regard

to sight and hearing, we cannot make statements with
thorough confidence or on irrefutable evidence. However, the solen
or razor-fish, if you make a noise, appears to burrow in the sand, and
to hide himself deeper when he hears the approach of the iron rod (for
the animal, be it observed, juts a little out of its hole, while the
greater part of the body remains within),-and scallops, if you present
your finger near their open valves, close them tight again as though
they could see what you were doing. Furthermore, when fishermen are
laying bait for neritae, they always get to leeward of them, and never
speak a word while so engaged, under the firm impression that the
animal can smell and hear; and they assure us that, if any one
speaks aloud, the creature makes efforts to escape. With regard to
testaceans, of the walking or creeping species the urchin appears to
have the least developed sense of smell; and, of the stationary
species, the ascidian and the barnacle.

So much for the organs of sense in the general run of animals.
We now proceed to treat of voice.