There are still some wonderful kinds of fishes which we find mentioned by Theophrastus: he says, that when the waters subside, which have been admitted for the purposes of irrigation in the vicinity of Babylon, there are certain fish which remain in such holes as may contain water; from these they come forth for the purpose of feeding, moving along with their fins by the aid of a rapid movement of the tail. If pursued, he says, they retreat to their holes, and when they have reached them, will turn round and make a stand. The head is like that of the sea frog, while the other parts are similar to those of the gobio, and they have gills like other fish. He says also, that in the vicinity of Heraclea and Cromna, and about the river Lycus, as well as in many parts of the Black Sea, there is one kind of fish which frequents the waters near the banks of the rivers, and makes holes for itself, in which it lives, even when the water retires and the bed of the river is dry; for which reason these fishes have to be dug out of the ground, and only show by the movement of the body that they are still alive. He says also, that in the vicinity of the same Heraclea, when the river Lycus ebbs, the eggs are left in the mud, and that the fish, on being produced from these, go forth to seek their food by means of a sort of fluttering motion,—their gills being but very small, in consequence of which they are not in need of water. It is in this way that eels also can live so long out of water; and that their eggs come to maturity on dry land, like those of the sea-tortoise. In the same regions of the Black Sea, he says, various kinds of fishes are overtaken by the ice, the gobio more particularly, and they only betray signs of life, by moving when they have warmth applied by the saucepan. All these things, however, though very remarkable, still admit of some explanation.