Certain of the Swans and Cranes afford illustrations of musical instruments of an even more remarkable kind. Herein the windpipe at the base of the neck enters a large chamber formed by the absorption of the diploe sandwiched between the outer walls of the keel of the breastbone and the enlargement of the space so created until it can accommodate the tubular windpipe. This, entering the cavity in the form of a loop, runs the whole length of the keel, the upper limb of the loop finally running to the lungs. That we have here an indubitable musical instrument there can be no question, for its possessor is enabled thereby to utter loud, trumpet-like, if harsh, sounds. Here again only the males are so provided. The profound interest of this really extraordinary association of unrelated structures has never attracted the attention it deserves. Originally, no doubt, one would have met with nothing more than a loop of the windpipe impinging against the anterior border of a normal, blade-like keel: later there would have been formed a broad shallow surface on the keel at the point of contact with the loop, and gradually the depression must have deepened till the bony chamber came into being. By what nexus of sympathy were these reciprocal responses made? Another very singular type of looped windpipe is that wherein the trachea forms a series of coils between the body and the skin. It is surely somewhat surprising to find that precisely similar coils are met with in widely different groups of birds. Among the Passeres they occur in the Manucode: among the Plovers in the Painted Snipe (_Rhynchea rostratula_): among the game-birds in some of the Curassows, and among the Anatidæ in the aberrant Australian Black-and-White Goose (_Anseranas_).