17. As I before observed, the sense of touch belongs to all animals. The testacea have the senses of smelling and tasting. This is plain from the baits used, as those for the purpuræ; for this creature is caught with putrid substances, and will be attracted from a great distance to such baits, as if by the sense of smell. It is evident from what follows that they possess the sense of taste; for whatever they select by smell, they all love to taste. 18. And all animals with mouths receive pain or pleasure from the contact of food. But, concerning the senses of sight and hearing, it is not possible to say anything certain, or very distinct; the solens, if a person touch them, appear to retract themselves, and try to escape when they see an instrument approaching them, for a small portion of them is beyond the shell, the remainder as it were in a retreat; the pectens, also, if a finger is brought near them, open and shut themselves as if they could see. 19. Those who seek for neritæ do not approach them with the wind, when they seek them for baits, nor do they speak, but come silently, as if the creatures could both smell and hear; they say that if they speak, they get away. Of all testacea, the echinus appears to have the best sense of smell amongst those that can move, and the tethya and balanus in those that are fixed. This is the nature of the organs of sense in all animals. CHAPTER IX. 1. The following is the nature of the voice of animals, for there is a distinction between voice and sound. Speech, again, is different from these. Voice is due to no other part except the pharynx, the creatures, therefore, without lungs are also without voice. Speech is the direction of the voice by the tongue; the vowels are uttered by the voice and the larynx, the mutes by the tongue and the lips; speech is made up of these: wherefore, no animals can speak that have not a tongue, nor if their tongue is confined. 2. The power of uttering a sound is connected with other parts also; insects have neither voice nor speech, but make a sound with the air within them, not with that which is external, for some of them breathe not, some of them buzz, as the bee with its wings, and others are said to sing, as the grasshopper. All these make a noise with the membrane which is beneath the division of their body in those which have a division, as some families of grasshoppers by the friction of the air. These insects, bees, and all other insects raise and depress their wings in flight, for the sound is the friction of the air within them. Locusts produce a sound by rubbing themselves with their legs, which are adapted for leaping. None of the malacia utter any sound or natural voice, nor do the malacostraca.