The hibernation theory survived for more than 2,000 years and is still occasionally repeated by credulous persons to account for failure to locate definitely the winter home of the chimney swifts (_Chaetura pelagica_), which each autumn gather in immense flocks in southern Georgia and northern Florida and then suddenly disappear. Thereare, however, records of occurrence during migration for a few points in the West Indies, Mexico, and Central America, and it is probable that these birds spend the winter season in the great rain-forest area of the Amazon Valley in Brazil, passing most of the daytime high in the air with other swifts that are local residents. Aristotle was also the originator of the theory of transmutation, basing it upon the fact that frequently one species will arrive from the north just as another species departs for more southerly latitudes. From this he reasoned that although it was commonly believed that such birds were of two different species, there really was only one, and that this one assumed the different plumages to correspond with the summer and winter seasons. Probably the most remarkable theory that has been advanced to account for migration is contained in a pamphlet mentioned by Clarke (_4, v. 1, pp. 9-11_), as published in 1703 under the title: "An Essay Toward the Probable Solution of this Question: Whence Come the Stork and the Turtle, the Crane, and the Swallow, when they Know and Observe the Appointed Time of their Coming." It was written "By a Person of Learning and Piety", whose "probable solution" was that migratory birds flew to the moon and there spent the winter. Some who easily accepted the disappearance of the larger birds as migratory travelers were unable to understand how the smaller species, some of them notoriously poor fliers, could make similar journeys. They contended that the larger species, as the storks and cranes, carried their smaller companions as living freight. In some of the Mediterranean countries it is still believed that these broad-pinioned birds serve as aerial transports for the hosts of small birds that congregate on the shores of the Mediterranean Sea, awaiting opportunity for this kind of passage to their winter homes in Africa. Similar beliefs are found among some tribes of North American Indians. ADVANTAGES OF MIGRATION