as a general principle of explanation. The uncertainty that still hangs over this question and that of the heredity of acquired characters bears witness to the unsettled state of opinion regarding the whole problem, and to the inadequacy of the attempts thus far made to find its consistent and adequate solution. Here, too, accordingly, we find ourselves confronted with wide gaps in our knowledge which open the way to vitalistic or transcendental theories of development. I think we should resist the temptation to seek such refuge. It is more than probable that there are factors of evolution still unknown. We can but seek for them. Nothing is more certain than that life and the evolution of life are natural phenomena. We must approach them, and as far as I can see must attempt to analyze them, by the same methods that are employed in the study of other natural phenomena. The student of nature can do no more than strive towards the truth. When he does not find the whole truth there is but one gospel for his salvation--still to strive towards the truth. He knows that each forward step on the highway of discovery will bring to view a new horizon of regions still unknown. It will be an ill day for science when it can find no more fields to conquer. And so, if you ask whether I look to a day when we shall know the whole truth in regard to organic mechanism and organic evolution, I answer: No! But let us go forward. COLUMBIA UNIVERSITY PRESS A Series of twenty-two lectures descriptive in untechnical language of the achievements in Science, Philosophy and Art, and indicating the present status of these subjects as concepts of human knowledge, are being delivered at Columbia University, during the academic year 1907-1908, by various professors chosen to represent the several departments of instruction. MATHEMATICS, by Cassius Jackson Keyser, _Adrain Professor of Mathematics_. PHYSICS, by Ernest Fox Nichols, _Professor of Experimental Physics_. CHEMISTRY, by Charles F. Chandler, _Professor of Chemistry_. ASTRONOMY, by Harold Jacoby, _Rutherfurd Professor of Astronomy_. GEOLOGY, by James Furman Kemp. _Professor of Geology_. BIOLOGY, by Edmund B. Wilson, _Professor of Zoology_. PHYSIOLOGY, by Frederic S. Lee, _Professor of Physiology_. BOTANY, by Herbert Maule Richards, _Professor of Botany_. ZOOLOGY, by Henry E. Crampton, _Professor of Zoology_. ANTHROPOLOGY, by Franz Boas. _Professor of Anthropology_. ARCHAEOLOGY, by James Rignall Wheeler, _Professor of Greek Archaeology and Art_. HISTORY, by James Harvey Robinson, _Professor of History_. ECONOMICS, by Henry Rogers Seager, _Professor of Political Economy_. POLITICS, by Charles A. Beard, _Adjunct Professor of Politics_. JURISPRUDENCE, by Munroe Smith, _Professor of Roman Law and Comparative Jurisprudence_. SOCIOLOGY, by Franklin Henry Giddings, _Professor of Sociology_.