INTERNAL MIGRATIONS. 151 



are entirely unknown. Is it possible that the Knot 

 {Tringa caniUas) breeds anywliere in the Antarctic 

 regions ? We know that this bird passes to and fro 

 between the Polar regions of either hemisphere in 

 vast numbers, and still no breeding-ground has yet 

 been discovered in the Arctic regions in any way 

 proportionate to those numbers. Mr. Hudson in 

 his lately published valuable work, The Naturalist 

 in La Plata, remarks the appearance of certain 

 Northern Waders on the Pampas (notably Limosa 

 hudsonica), at a season which strongly suggests 

 their having bred in Antarctic latitudes. Again, it 

 is quite possible that many individuals of species 

 that winter in South Africa and breed in Europe, 

 as the Swallow {Hinmclo rustica), the Willow Wren 

 [Phijlloscopus trockilus), and the Sedge Warbler 

 (Acrocephalus phragmitis), for instance, might visit 

 the Northern Hemisphere in our summer, after 

 having bred in South Africa, but do not attempt to 

 breed again, and be overlooked. No one would 

 suspect such a thing to be taking place, and yet it 

 is not impossible, if not very probable. We should 

 expect to find this state of things prevailing, if at 

 all, in the Northern Hemisphere, on the southern 

 limits of the summer area of dispersal of these 

 species; in Algeria, for instance, where curiously 

 enough all three of the above-named birds are 

 found throughout the year. Probably somewhere 

 in Central Africa these birds may be found all the 

 year round, yet never breeding in those equatorial 

 districts. It is also a curious fact that the Quail 



