You will have received my letter from Carlsruhe. Could I only tell you all that I have since thought and observed about the history of our earth's development, the succession of the animal populations, and their genetic classification! It cannot easily be compressed within letter limits; I will, nevertheless, attempt it when my lectures make less urgent claim upon me, and my eyes are less fatigued. I should defer writing till then were it not that to-day I have something of at least outside interest to announce. It concerns the inclosed letter received to-day. (The offer of a professorship at Heidelberg.) Should you think that I need not take it into consideration, and you have no time to answer me, let me know your opinion by your silence. I will tell you the reasons which would induce me to remain for the present in Neuchatel, and I think you will approve them. First, as my lectures do not claim a great part of my time I shall have the more to bestow on other work; add to this the position of Neuchatel, so favorable for observations such as I propose making on the history of development in several classes of animals; then the hope of freeing myself from the burden of my collections; and next, the quiet of my life here with reference to my somewhat overstrained health. Beside my wish to remain, these favorable circumstances furnish a powerful motive, and then I am satisfied that people here would assist me with the greatest readiness should my publications not succeed otherwise. As to the publication of my fishes, I can, after all, better direct the lithographing of the plates here. I have just written to Cotta concerning this, proposing also that he should advance the cost of the lithographs. I shall attend to it all carefully, and be content for the present with my small means. From the gradual sale he can, little by little, repay my expenses, and I shall ask no profit until the success of the work warrants it. I await his answer. This proposal seems to me the best and the most likely to advance the publication of this work. Since I arrived here some scientific efforts have been made with the help of M. Coulon. We have already founded a society of Natural History,* (* Societe des Sciences Naturelles de Neuchatel.) and I hope, should you make your promised visit next year, you will find this germ between foliage and flower at least, though perhaps not yet ripened into seed. . . M. Coulon told me the day before yesterday that he had spoken with M. de Montmollin, the Treasurer, who would write to M. Ancillon concerning the purchase of my collection. . .Will you have the kindness, when occasion offers, to say a word to M. Ancillon about it?. . .Not only would this collection be of the greatest value to the museum here, but its sale would also advance my farther investigations. With the sum of eighty louis, which is all that is subscribed for my professorship, I cannot continue them on any large scale.