This, then, is my night-work. I have still to tell you what I do by day, and this is more important. My first duty is to complete my Brazilian Fishes. To be sure, it is only an honorary work, but it must be finished, and is an additional means of making subsequent works profitable. This is my morning occupation, and I am sure of bringing it to a close about Easter. After much reflection, I have decided that the best way to turn my Fresh-Water Fishes to account, is to finish them completely before offering them to a publisher. All the expenses being then paid, I could afford, if the first publisher should not feel able to take them on my own terms, to keep them as a safe investment. The publisher himself seeing the material finished, and being sure of bringing it out as a complete work, the value of which he can on that account better estimate, will be more disposed to accept my proposals, while I, on my side, can be more exacting. The text for this I write in the afternoon. My greatest difficulty at first was the execution of the plates. But here, also, my good star has served me wonderfully. I told you that beside the complete drawings of the fishes I wanted to represent their skeletons and the anatomy of the soft parts, which has never been done for this class. I shall thereby give a new value to the work, and make it desirable for all who study comparative anatomy. The puzzle was to find some one who was prepared to draw things of this kind; but I have made the luckiest hit, and am more than satisfied. My former artist continues to draw the fishes, a second draws the skeletons (one who had already been engaged for several years in the same way, for a work upon reptiles), while a young physician, who is an admirable draughtsman, makes my anatomical figures. For my share, I direct their work while writing the text, and thus the whole advances with great strides. I do not, however, stop here. Having by permission of the Director of the Museum one of the finest collections of fossils in Germany at my disposition, and being also allowed to take the specimens home as I need them, I have undertaken to publish the ichthyological part of the collection. Since it only makes the difference of one or two people more to direct, I have these specimens also drawn at the same time. Nowhere so well as here, where the Academy of Fine Arts brings together so many draughtsmen, could I have the same facility for completing a similar work; and as it is an entirely new branch, in which no one has as yet done anything of importance, I feel sure of success; the more so because Cuvier, who alone could do it (for the simple reason that every one else has till now neglected the fishes), is not engaged upon it. Add to this that just now there is a real need of this work for the determination of the different geological formations. Once before, at the Heidelberg meeting, it had been proposed to me; the Director of the Mines at Strasbourg, M. Voltz,