The sperm has only a single S-shaped blowhole situated almost at the end of the snout on the left side, and its spout, which is like that of no other whale, may be easily recognized even at a considerable distance; the low, bushy, vapor column is directed diagonally forward and upward, and the animal blows much oftener and more regularly than other large cetaceans. A sperm may spout thirty or forty times when not disturbed, generally lying still but occasionally swimming slowly during the entire breathing period. [Illustration: An anterior view of a young male sperm whale. The head occupies one-third the entire length of the animal and the lower jaw is much shorter than the upper. ] When a bull is wallowing at the surface, the “hump” (corresponding to the dorsal fin of the fin whales) is first seen, and at regular intervals, as the spout is ejected, the nose appears some forty feet ahead. The length of time he stays at the surface, the number of spouts, and the interval between them are all very regular and thus the hunters, after a particular whale has been observed for a few minutes, know exactly when the animal will again appear and how long it will remain visible. After its blowing has been finished, the head gradually sinks, the back and “small” are curved upward, the flukes are lifted slowly high into the air, and the whale goes straight down. During the “big dive” the animal remains below from fifteen to forty minutes and when reappearing, if not disturbed, swims tranquilly along just below the surface at a rate of about three or four miles an hour. His body is then horizontal, with the hump projecting above the water. When frightened and speeding, a totally different attitude is assumed and the great flukes are moved violently up and down; at each downward stroke the head sinks eight or ten feet below the surface but rises with the upward motion, presenting only the cutwater-like lower portion. The upstroke of the tail appears to be the more powerful of the two, and at the same time the broad upper half of the head is lifted above the surface. A speed of ten or twelve miles an hour can be reached in this way, which the whalers describe as “going head out.” The sperm is very playful and like the humpback frequently “breaches,” or throws itself out of water, shooting into the air at an angle of about 45 degrees and falling back upon its side. It sometimes lobtails also, pounding the water into spray with its flukes. When a sperm is harpooned with a hand iron it often rolls over and over on the surface, winding the line about its body and causing the hunters a deal of trouble. [Illustration: The tongue of a sperm whale; it is strikingly different from the enormous flabby tongue of the whalebone whales. ]