পাতা:পদার্থবিদ্যাসার.djvu/১১৭

DIALOGU1E VIII. of raha. ' Pup. To what shall we next turn omr attention ? Tut. Suppose we now take a view of the inhabitants of the watery world. What think you of creatures living in an element which would be fatal to us, and which could not live upon the earth as we do?— Water is the dwelling place of inillions of fishes. Pup. How are fishes distinguished ? Tut, Chiefly by their fins, which are named from their situation on the animal. We have accordingly breast fins; the belly fins; the vent fin, and the tail fin. Pup. Are any of these fins used for similar purposes as feet in quadrupeds Tut. The ventral fins are cousidered as analogous to feet in quadrupeds, and it is from the situation, presence, or absence, of these fins that the orders of fishes are characterized. Pup. How many orders of fishes are there? Tat. There are six:– Ist. Those that have no ventral fins, as eels, &c. 2nd. Those that have their ventral fins placed before the pectoral, as the cod fish. & - 3rd. . Those whose ventral fins are under the pectoral, as the dory, perch, &e.