30 The Wilson Bulletin — No. 86 



8. New Zealand Region, characterized by the Apterygidae, 

 Nestoridae and Stringopidae, several Ducks, Rails, Plovers, 

 Hawks and others. 



9. Nearctic Region, North America from the limit of tree 

 growth in the north to northern JNIexieo, with the exception of 

 the extreme southern part of Florida. No peculiar forms. 



10. Neotropical Region, the remainder of the Western 

 Hemisphere, is by far the richest in bird life and bird forms 

 and also in peculiar families : Rheidae, Palamedeidae, Eury- 

 pygidae, Aramidae, Thinocoridae, Tinamidae, Opisthocomidae, 

 Cracidae, Rhamphastidae, Bucconidae, Galbulidae, Momoti- 

 dae, Cotingidae, Dendrocolaptidae, Formicariidae, Pteropto- 

 chidae, Dacuididae. Also as having the center of abundance 

 there : Conuridae, Trochilidae Tyrannidae, Icteridae, Tana- 

 gridae. 



11. Birds of the Ocean. 



The migration of birds is then spoken of and no attention 

 whatever paid to the fallacies of a Gatke in his "Birds of 

 Heligoland," and the migration routes in general are given. 

 As to the origin of bird migration Weissmann's theory (1878) 

 is considered the most plausible one, namely, the emigration 

 of birds after the glacial period from the tropics during the 

 warmer season of the year and the return at the approach 

 of cold weather along the same routes, which in time became 

 an established habit through natural selection among those 

 who possessed the inherited custom. 



We beg to differ with the learned author. We think that 

 Mr. Frank ^I. Chapman has so far given the best reason for 

 the migration of birds. "Auk," XI, 1894, pp. 12-17, shows 

 that the causes of bird migration are internal and not external, 

 that many animals have an instinctive desire for seclusion 

 during the season of reproduction, and that in the case of 

 Sea-birds, for instance, dissection will show an enlargement 

 of the sexual organs and that it is this physiological change 

 which warns the birds that the season of reproduction is at 

 hand. "The object is the same wdth the Warbler, as well as 

 with the Sea-birds. Dr. Allen later on calls attention to the 

 fact, the great fundamental fact, that the life of animals, 



