3. Fish also are mute, for they have neither lungs, trachea, nor pharynx. Some of them utter a sound and a squeak; these are said to have a voice, as the lyra[151] and chromi,[152] for these utter, as it were, a grunt; so does the capros, a fish of the Achelous, the chalceus[153] and coccyx,[154] for the one utters a sound like hissing, the other a noise like that of the cuckoo, from whence also its name is derived. Some of these utter their apparent voice by the friction of their gills, for these places are spinous, in others the sound is internal, near the stomach. For each of them has an organ of breathing, which causes a sound when it is pressed and moved about. [151] Trigla Lyra. [152] Cottus cataphractus. [153] Zeus faber. [154] Trigla hirundo. 4. Some of the selachea also appear to whistle, but they cannot be correctly said to utter a voice, only to make a sound. The pectens also make a whizzing noise when they are borne upon the surface of the water, or flying, as it is called; and so do the sea-swallows,[155] for they also fly through the air in the same way, not touching the sea, for they have wide and long fins. As the sound made by birds flying through the air is not a voice, so neither can either of these be properly so called. The dolphin also utters a whistle and lows when it comes out of the water into the air, in a different way from the animals above-mentioned--for this is a true voice, for it has lungs and a trachea, but its tongue is not free, nor has it any lips so as to make an articulate sound. [155] Flying fish. 5. The oviparous quadrupeds, with a tongue and lungs, utter a sound, though it is a weak one. Some of them hiss like serpents; others have a small weak voice, others, as the tortoise, utter a small hiss. The tongue of the frog is peculiar, for the fore-part of it is fixed, like that of a fish; but the part near the pharynx is free and folded up. With this it utters its peculiar sound. The male frogs make a croaking in the water when they invite the females to coition. 6. All animals utter a voice to invite the society and proximity of their kind, as the hog, the goat, and the sheep. The frog croaks by making its lower jaw of equal length, and stretching the upper one above the water. Their eyes appear like lights, their cheeks being swelled out with the vehemence of their croaking; for their copulation is generally performed in the night. The class of birds utter a voice: those which have a moderately wide tongue have the best voice; those also in which the tongue is thin. In some kinds both male and female have the same voice; in others it is different: the smaller kinds have more variety in their voice, and make more use of it, than the larger tribes.