was a careful, minute, persevering observer, as well as a deep thinker; but he was as indolent with his pen as he was industrious with his brain. He gave his intellectual capital to his pupils without stint or reserve, and nothing delighted him more than to sit down for a quiet talk on scientific matters with a few students, or to take a ramble with them into the fields outside the city, and explain to them as he walked the result of any recent investigation he had made. If he found himself understood by his listeners he was satisfied, and cared for no farther publication of his researches. I could enumerate many works of masters in our science, which had no other foundation at the outset than these inspiriting conversations. No one has borne warmer testimony to the influence Dollinger has had in this indirect way on the progress of our science than the investigator I have already mentioned as his greatest pupil,--von Baer. In the introduction to his work on embryology he gratefully acknowledges his debt to his old teacher. "Among the most fascinating of our professors was Oken. A master in the art of teaching, he exercised an almost irresistible influence over his students. Constructing the universe out of his own brain, deducing from a priori conceptions all the relations of the three kingdoms into which he divided all living beings, classifying the animals as if by magic, in accordance with an analogy based on the dismembered body of man, it seemed to us who listened that the slow laborious process of accumulating precise detailed knowledge could only be the work of drones, while a generous, commanding spirit might build the world out of its own powerful imagination. The temptation to impose one's own ideas upon nature, to explain her mysteries by brilliant theories rather than by patient study of the facts as we find them, still leads us away. With the school of the physio-philosophers began (at least in our day and generation) that overbearing confidence in the abstract conceptions of the human mind as applied to the study of nature, which still impairs the fairness of our classifications and prevents them from interpreting truly the natural relations binding together all living beings. And yet, the young naturalist of that day who did not share, in some degree, the intellectual stimulus given to scientific pursuits by physio-philosophy would have missed a part of his training. There is a great distance between the man who, like Oken, attempts to construct the whole system of nature from general premises and the one who, while subordinating his conceptions to the facts, is yet capable of generalizing the facts, of recognizing their most comprehensive relations. No thoughtful naturalist can silence the suggestions, continually arising in the course of his investigations, respecting the origin and deeper connection of all living beings; but he is the truest student of nature who, while