My gratitude to my friends at Aberdeen, in particular to Professor and Mrs. J. A. Thomson, for their hospitality and great kindness towards me cannot be expressed here; they all know that they succeeded in making me feel quite at home with them. I am very much obliged to my publishers, Messrs. A. and C. Black, for their readiness to fulfil all my wishes with respect to publication. The lectures contained in this book were written in English by a German and delivered at a Scottish university. Almost all of the ideas discussed in it were first conceived during the author’s long residence in Southern Italy. Thus this book may be witness to the truth which, I hope, will be universally recognised in the near future--that all culture, moral and intellectual and aesthetic, is not limited by the bounds of nationality. HANS DRIESCH. Heidelberg, *2nd January 1908*. CONTENTS OF THE FIRST VOLUME THE PROGRAMME PAGE On Lord Gifford’s Conception of “Science” 1 Natural Sciences and “Natural Theology” 3 Our Philosophical Basis 5 On Certain Characteristics of Biology as a Science 9 The Three Different Types of Knowledge about Nature 13 General Plan of these Lectures 15 General Character of the Organic Form 19 SECTION A.--THE CHIEF RESULTS OF ANALYTICAL BIOLOGY PART I.--THE INDIVIDUAL ORGANISM WITH REGARD TO FORM AND METABOLISM *A.* ELEMENTARY MORPHOGENESIS-- Evolutio and Epigenesis in the old Sense 25 The Cell 27 The Egg: its Maturation and Fertilisation 31 The First Developmental Processes of Echinus 33 Comparative Embryology 44 The First Steps of Analytical Morphogenesis 45 The Limits of Pure Description in Science 50 *B.* EXPERIMENTAL AND THEORETICAL MORPHOGENESIS-- 1. THE FOUNDATIONS OF THE PHYSIOLOGY OF DEVELOPMENT. “EVOLUTIO” AND “EPIGENESIS” 52 The Theory of Weismann 52 Experimental Morphology 56 The Work of Wilhelm Roux 58 The Experiments on the Egg of the Sea-urchin 59 On the Intimate Structure of the Protoplasm of the Germ 65 On some Specificities of Organisation in Certain Germs 70 General Results of the First Period of “Entwickelungsmechanik” 71 Some New Results concerning Restitutions 74