products and her own, but devotes an enormous attention to the plantation colony because of the apparent importance of its unique products. Hence the farm colony is left free to develop along natural lines, while the plantation colony is subjected to all sorts of artificial restrictions and limitations which hamper its growth. As a result of all these factors, the plantation colony seldom achieves its independence, but remains subject to the home state indefinitely. Examples of farm colonies are the Thirteen Colonies, Canada, New Zealand, etc.; of plantation colonies, Java, Jamaica, Brazil under the Portuguese, etc. As will be seen, the farm colony has a peculiarly intimate relation with immigration movements. This preliminary survey of the earlier forms of migration prepares the way for a clear understanding of the characteristic features of the fourth form. This is immigration, which in many respects differs from any other population movement. These distinctions merit emphasis. In the first place, both of the two states concerned in an immigration movement are well established, and on approximately the same stage of civilization. Immigration can take place only over what Professor Sumner calls a single culture-area. Secondly, immigration is a distinctly individual undertaking. States may direct, control, regulate, or encourage immigration, but the motives which lead men into this form of movement are strictly individual ones, and the causes which arouse these motives are conditions which react upon the individual alone. The end sought is neither the advantage of the country of origin, nor of the country of destination, but the improvement of the condition of the individual. The two countries concerned in an immigration movement resemble each other not only in the stage of culture but in climatic conditions and circumstances of life. There has never been any immigration between the temperate zones and the tropics, in either direction, nor have the polar regions ever figured. In fact, practically all immigration, historically speaking, has been between different countries in the temperate zone. But while there are these resemblances between the countries concerned, there must also always be some differences, otherwise there would be no motive for movement. The first and primary difference between the two countries is that the one which receives the stream of immigration is newer, and therefore much less thickly settled, than the other. Other things being equal, the chances for a comfortable living are greater in a country where the ratio between men and land is still low. This ratio between men and land is of extreme importance, and ought never to be neglected in the discussion of any sociological or economic problem.[10] It is especially vital as regards migrations, which are so directly connected with the shifting of populations.