MORE than four years ago an article, headed as above, appeared in this journal (vol. x. p. 415) giving rise to some comments of more or less importance (torn, cit., pp. 459, 520, and xi. p. 5). Since that time two very remarkable treatises on the subject have come forth, the one by Dr. Palmen, on the routes taken by birds in their migrations, and the other by Dr. August Weissmann, dealing generally with the whole question.1 The first, originally published in Swedish,2 was translated into German soon after, and in due time was reviewed in these columns (vol. xv. p. 465). An excellent English version of the second has recently appeared in the “Contemporary Review” (February, 1879, p. 531), and therefore my readers may be presumed to be acquainted with the views of both authors. It cannot be denied that each of them has to some extent enlarged the boundaries of our knowledge of the subject, and still more widely those of our speculations upon it.