THE question of the assimilation o of immigrants under American conditions has long been looked upon as of vital importance, and it has been much discussed, but heretofore with Kttle accurate information. Speaking from general personal observation, people have thought that under the influence of the existing educational, social, and political conditions the immigrants gradually change their habits of life and their ways of thinking, and thus become Americans. The statement is often made that American citizens tend to resemble the American Indian, meaning thereby some generalised type of lains Indian, but this has never been put to scientific, test. Little or no thought, however, has been given to the possible effect of the physical and social,environment on the physical type of descendants of immigrants. The establishment by Congress of the Immigration Commission in February, 1907, gave the. opportunity for a thorough investigation of the problems of immigration, and the inquiry into the anatomical characters of immigrants and their descendants was put under the direction of Prof. Franz Boas, of Columbia University, than whom no better selection could have been made. The present short report deals with only a portion of the material collected, but results obtained are of unexpected interest and importance.