the "exactness" of his observations. Like observation, experimentation has been wonderfully improved of late years. The experimental sciences which make most use of it--experimental physics, chemistry, physiology, pathology, etc.--have made astounding progress. But it is just as important in the case of experiment--or observation under artificial conditions--as of simple observation that it be undertaken and carried out with a sound and clear judgment. Nature can only give a correct and unambiguous answer to the question you put it when it is clearly and distinctly proposed. This is very often not the case, and the experimenter loses himself in meaningless efforts, with the foolish hope that "something may come of it." The modern province of experimental or mechanical embryology is especially marred by these useless and perverse experiments. Equally foolish is the conduct of those biologists who would transfer the experiment that is valuable in physiology to the field of anatomy, where it is rarely profitable. In the modern controversy about evolution the attempt is frequently made to prove or refute experimentally the origin of species. It is quite forgotten that the idea of species is only relative, and that no man of science can give an absolute definition of it. Nor is it less perverse to attempt to apply experimentation to historical problems where all the conditions for a successful application are lacking. The knowledge which we obtain directly by observation and experiment is only sound when it refers to present events. We have to turn to other methods for the investigation of the past--to history and traditions; and these are less easily accessible. This branch of science has been investigated for thousands of years, as far as the history of man and civilization, of peoples and states, and their customs, laws, languages, and migrations, is concerned. In this, the oral and written tradition from generation to generation, the ancient monuments, and documents, and weapons, etc., furnish an abounding empirical material from which critical judgment can draw a host of conclusions. However, the door to error lies wide open here, as the documents are usually imperfect, and the subjective interpretation of them is often no clearer than their objective validity.