"I felt that to reach my aim more surely it was important to complete my medical studies, and for this I came to Munich eighteen months ago. Still I could not make up my mind to renounce the natural sciences. I attended some of the pathological lectures, but I soon found that I was neglecting them; and yielding once more to my inclination, I followed consecutively the lectures of Dollinger on comparative anatomy, those of Oken on natural history, those of Fuchs on mineralogy, as well as the courses of astronomy, physics, chemistry, and mathematics. I was confirmed in this withdrawal from medical studies by the proposition of M. de Martius that I should describe the fishes brought back by Spix from Brazil, and to this I consented the more gladly because ichthyology has always been a favorite study with me. I have not, however, been able to give them all the care I could have wished, for M. de Martius, anxious to complete the publication of these works, has urged upon me a rapid execution. I hope, nevertheless, that I have made no gross errors, and I am the less likely to have done so, because I had as my guide the observations you had kindly made for him on the plates of Spix. Several of these plates were not very exact; they have been set aside and new drawings made. I beg that you will judge this work when it reaches you with indulgence, as the first literary essay of a young man. I hope to complete it in the course of the next summer. I would beg you, in advance, to give me a paternal word of advice as to the direction my studies should then take. Ought I to devote myself to the study of medicine? I have no fortune, it is true; but I would gladly sacrifice my life if, by so doing, I could serve the cause of science. Though I have not even a presentiment of any means with which I may one day travel in distant countries, I have, nevertheless, prepared myself during the last three years as if I might be off at any minute. I have learned to skin all sorts of animals, even very large ones. I have made more than a hundred skeletons of quadrupeds, birds, reptiles, and fishes; I have tested all the various liquors for preserving such animals as should not be skinned, and have thought of the means of supplying the want in countries where the like preparations are not to be had, in case of need. Finally, I have trained as traveling companion a young friend,* (* William Schimper, brother of Karl.) and awakened in him the same love of the natural sciences. He is an excellent hunter, and at my instigation has been taking lessons in drawing, so that he is now able to sketch from nature such objects as may be desirable. We often pass delightful moments in our imaginary travels through unknown countries, building thus our castles in Spain. Pardon me if I talk to you of projects which at first sight seem puerile; only a fixed aim is needed to give them reality, and to you I come for counsel. My longing is so great that