The nostrils communicate directly to the lungs rather than share a portion of the throat as is customary in other air-breathing vertebrates. This means that the whale’s mouth and throat can be full of water without danger of flooding the lungs, and that it is unnecessary to empty such a spacious cavern prior to breathing. Furthermore, it is unlikely that a whale could keep his mouth closed enough to prevent flooding through the baleen because there is no upper lip over this device. Although a whale can be sighted by the telltale spout, a frightened whale may elude detection by exhaling just before surfacing, so that nothing more than a foamy patch is produced. Under these situations the whale does not expose the usual amount of buoyant head, but only the nostrils. A disturbed whale can dive, and then surface a mile or two away, or it may not move at all, preferring to hide on the bottom or among rocky reefs or in the kelp. The California gray whale was judged by whalers to be the most wary and elusive of them all. _Swimming Adaptations_ The most essential features needed for the successful invasion of the marine habitat were those necessary for efficient propulsion. Fish, eons before, had solved the hydrodynamic equations necessary for movement through such a resistive medium. This solution required a streamlined form with a tail for propulsion, placed at the very end of the body. Extra fins were employed for maneuvering and for balancing. Whales, too, have reached the same solution, and man, when he finally develops sufficient highspeed submarines, will employ the same solution, namely streamlining. As a consequence, all whales look alike, differing principally in the degree of streamlining, color or size. In a whale’s streamlined body there can be no sharp discontinuities to accommodate the head, the neck, the trunk, and lastly the tail. Instead these features must grade imperceptibly one into the other. The only allowable discontinuity is the end of the tail which is expanded into fanshaped lobes to function like a propeller. [Illustration: Gray whale rolled over on side during courtship. Note outline under water of tail and tailflukes. _Courtesy Scripps Institute of Oceanography._] These features, called tail flukes, are driven up and down in contrast to the tail of a fish which is driven sidewise. Whales have long banks of muscle along either side of the backbone which attach to the tail flukes by means of tendons. This makes it unnecessary to disturb the streamlined form by bending the hind part of the trunk as is necessary when fish drive with their tails. It also makes it possible to devote a great deal more muscle to the task. The power developed by these muscles is prodigious, capable of driving a 100-ton body through the water at speeds up to 20 knots. Wounded whales can smash a 20-foot whaleboat to bits with a single slap of the tail.