My appointment as Gifford Lecturer, the news of which reached me in February 1906, came just at the right moment in the progress of my theoretical studies. I had always tried to improve my previous books by adding notes or altering the arrangement; I also had left a good deal of things unpublished, and thus I often hoped that I might have occasion to arrange for a new, improved, and enlarged edition of those books. This work then is the realisation of my hopes; it is, in its way, a definitive statement of all that I have to say about the Organic. The first volume of this work, containing the lectures for 1907--though the division into “lectures” has not been preserved--consists of Parts I. and II. of Section A, “The Chief Results of Analytical Biology.” It gives in Part I. a shortened, revised, and, as I hope, improved account of what was published in my *Analytische Theorie der organischen Entwickelung* (1894), *Die Localisation morphogenetischer Vorgänge; ein Beweis Vitalistischen Geschehens* (1899), and *Die organischen Regulationen* (1901), though for the professed biologist the two last-named books are by no means superseded by the new work. Part II. has never been published in any systematic form before, though there are many remarks on Systematics, Darwinism, etc., in my previous papers. The second volume--to be published in the autumn, after the delivery of the 1908 lectures--will begin with the third and concluding part of the scientific section, which is a very carefully revised and rearranged second edition of my book, *Die “Seele” als elementarer Naturfactor* (1903). The greater part of this volume, however, will be devoted to the “Philosophy of the Organism,” *i.e.* Section B, which, in my opinion, includes the most important parts of the work. Some apology is needed for my presuming to write in English. I was led to do so by the conviction, mistaken perhaps, that the process of translation would rob the lectures of that individual and personal character which, as I said before, seems to me so much to be desired. I wished nothing to come between me and my audience. I accordingly wrote my manuscript in English, and then submitted it to linguistic revision by such skilled aid as I was able to procure at Heidelberg. My reviser tells me that if the result of his labours leaves much to be desired, it is not to be wondered at, but that, being neither a biologist nor a philosopher, he has done his best to make me presentable to the English reader. If he has failed in his troublesome task, I know that it is not for want of care and attention, and I desire here to record my sense of indebtedness to him. He wishes to remain anonymous, but I am permitted to say that, though resident in a foreign university, he is of Scottish name and English birth.