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+*** START OF THE PROJECT GUTENBERG EBOOK 44388 ***
+
+Transcriber’s notes:
+
+In this transcription, italic text is denoted by *asterisks* and bold
+text by =equal signs=. Subscripts are indicated by _underscores_ (e.g.
+*a*_1 and *b*_1 in Fig.5 caption) and superscripts by ^ (e.g. *a*^1. in
+Fig. 9 caption).
+
+Page footnotes (renumbered in consecutive order) are now located
+immediately below the relevant paragraphs.
+
+The rare spelling typos noted in the original text have been corrected
+silently (e.g. invividual-->individual, hyberbola-->hyperbola) but
+inconsistent use of the ligature æ/ae (e.g. palæontology/palaeontology),
+inconsistent use of alternative spellings (e.g. learned/learnt), and
+occasional inconsistencies of hyphenation have been left as in the
+original. Minor punctuation typos have been corrected silently (e.g.
+index entries with missing commas). The abbreviation viz. appears in
+both roman and italic font.
+
+Formatting of entries in the Table of Contents does not accurately
+match that of the corresponding headings in the text, particularly the
+heading Pt.I-B-3 which contains an extraneous α.
+
+In Figure 12 caption, multiple ditto marks have been replaced by the
+relevant text for greater clarity.
+
+
+
+
+
+ THE SCIENCE AND PHILOSOPHY
+ OF THE ORGANISM
+
+
+
+
+ AGENTS
+
+ America The Macmillan Company
+ 64 & 66 Fifth Avenue, New York
+
+ Australasia The Oxford University Press, Melbourne
+
+ Canada The Macmillan Company of Canada, Ltd.
+ 27 Richmond Street West, Toronto
+
+ India Macmillan & Company, Ltd.
+ Macmillan Building, Bombay
+ 309 Bow Bazaar Street, Calcutta
+
+
+
+
+ THE
+ SCIENCE AND PHILOSOPHY
+ OF THE ORGANISM
+
+ THE GIFFORD LECTURES DELIVERED BEFORE
+ THE UNIVERSITY OF ABERDEEN
+ IN THE YEAR 1907
+
+ BY
+ HANS DRIESCH, Ph.D.
+ HEIDELBERG
+
+
+ LONDON
+ ADAM AND CHARLES BLACK
+ 1908
+
+ *All rights reserved*
+
+
+
+
+PREFACE
+
+
+This work is not a text-book of theoretical biology; it is a systematic
+presentment of those biological topics which bear upon the true
+philosophy of nature. The book is written in a decidedly subjective
+manner, and it seems to me that this is just what “Gifford Lectures”
+ought to be. They ought never to lose, or even try to lose, their
+decidedly personal character.
+
+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.
+
+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
+
+ 2. ANALYTICAL THEORY OF MORPHOGENESIS 76
+
+ α. THE DISTRIBUTION OF MORPHOGENIC POTENCIES 76
+
+ Prospective Value and Prospective Potency 76
+ The Potencies of the Blastomeres 79
+ The Potencies of Elementary Organs in General 80
+ Explicit and Implicit Potencies: Primary and Secondary
+ Potencies 83
+ The Morphogenetic Function of Maturation in the Light of
+ Recent Discoveries 85
+ The Intimate Structure of Protoplasm: Further Remarks 88
+ The Neutrality of the Concept of “Potency” 89
+
+ β. THE “MEANS” OF MORPHOGENESIS 89
+
+ β′. The Internal Elementary Means of Morphogenesis 90
+
+ Some Remarks on the Importance of Surface Tension in
+ Morphogenesis 91
+ On Growth 93
+ On Cell-division 94
+
+ β″. The External Means of Morphogenesis 95
+
+ The Discoveries of Herbst 96
+
+ γ. THE FORMATIVE CAUSES OR STIMULI 99
+
+ The Definition of Cause 99
+ Some Instances of Formative and Directive Stimuli 102
+
+ δ. THE MORPHOGENETIC HARMONIES 107
+
+ ε. ON RESTITUTIONS 110
+
+ A few Remarks on Secondary Potencies and on Secondary
+ Morphogenetic Regulations in General 110
+ The Stimuli of Restitutions 113
+
+ 3. THE PROBLEM OF MORPHOGENETIC LOCALISATION: THE
+ THEORY OF THE HARMONIOUS-EQUIPOTENTIAL SYSTEM--FIRST
+ PROOF OF THE AUTONOMY OF LIFE 118
+
+ The General Problem 118
+ The Morphogenetic “System” 119
+ The “Harmonious-equipotential System” 122
+ Instances of “Harmonious-equipotential Systems” 126
+ The Problem of the Factor *E* 132
+ No Explanation offered by “Means” or “Formative Stimuli” 132
+ No Explanation offered by a Chemical Theory of Morphogenesis 134
+ No Machine Possible Inside the Harmonious Systems 138
+ The Autonomy of Morphogenesis proved 142
+ “Entelechy” 143
+ Some General Remarks on Vitalism 145
+ The Logic of our First Proof of Vitalism 146
+
+ 4. ON CERTAIN OTHER FEATURES OF MORPHOGENESIS ADVOCATING
+ ITS AUTONOMY 150
+
+ Harmonious-equipotential Systems formed by Wandering Cells 151
+ On Certain Combined Types of Morphogenetic Systems 153
+ The “Morphaesthesia” of Noll 157
+ Restitutions of the Second Order 158
+ On the “Equifinality” of Restitutions 159
+ Remarks on “Retro-Differentiation” 163
+
+ *C.* ADAPTATION--
+
+ INTRODUCTORY REMARKS ON REGULATIONS IN GENERAL 165
+
+ 1. MORPHOLOGICAL ADAPTATION 168
+
+ The Limits of the Concept of Adaptation 168
+ Adaptations to Functional Changes from Without 172
+ True Functional Adaptation 176
+ Theoretical Conclusions 179
+
+ 2. PHYSIOLOGICAL ADAPTATION 184
+
+ Specific Adaptedness *not* “Adaptation” 186
+ Primary and Secondary Adaptations in Physiology 188
+ On Certain Pre-requisites of Adaptations in General 189
+ On Certain Groups of Primary Physiological Adaptations 190
+
+ General Remarks on Irritability 190
+ The Regulation of Heat Production 193
+ Primary Regulations in the Transport of Materials and
+ Certain Phenomena of Osmotic Pressure 194
+ Chromatic Regulations in Algae 197
+ Metabolic Regulations 198
+
+ Immunity the only Type of a Secondary Physiological
+ Adaptation 204
+ No General Positive Result from this Chapter 209
+ A few Remarks on the Limits of Regulability 212
+
+ *D.* INHERITANCE. SECOND PROOF OF THE AUTONOMY OF LIFE--
+
+ The Material Continuity in Inheritance 214
+ On Certain Theories which Seek to Compare Inheritance to Memory 216
+ The Complex-Equipotential System and its Rôle in Inheritance 219
+ The Second Proof of Life-Autonomy. Entelechy at the Bottom
+ of Inheritance 224
+ The Significance of the Material Continuity in Inheritance 227
+ The Experimental Facts about Inheritance 228
+ The Rôle of the Nucleus in Inheritance 233
+ Variation and Mutation 237
+
+ *CONCLUSIONS FROM THE FIRST MAIN PART OF THESE LECTURES* 240
+
+
+ PART II.--SYSTEMATICS AND HISTORY
+
+ *A.* THE PRINCIPLES OF SYSTEMATICS--
+
+ Rational Systematics 243
+ Biological Systematics 246
+
+ *B.* THE THEORY OF DESCENT--
+
+ 1. GENERALITIES 250
+
+ The Covert Presumption of all Theories of Descent 253
+ The Small Value of Pure Phylogeny 255
+ History and Systematics 257
+
+ 2. THE PRINCIPLES OF DARWINISM 260
+
+ Natural Selection 261
+ Fluctuating Variation the Alleged Cause of Organic Diversity 264
+ Darwinism Fails all along the Line 269
+
+ 3. THE PRINCIPLES OF LAMARCKISM 271
+
+ Adaptation as the Starting-Point 272
+ The Active Storing of Contingent Variations as a
+ Hypothetic Principle 273
+ Criticism of the “Inheritance of Acquired Characters”
+ assumed by Lamarckism 275
+ Other Principles Wanted 281
+ Criticism of the Hypothesis of Storing and Handing Down
+ Contingent Variations 282
+
+ 4. THE REAL RESULTS AND THE UNSOLVED PROBLEMS OF TRANSFORMISM 290
+
+ 5. THE LOGICAL VALUE OF THE ORGANIC FORM ACCORDING TO THE
+ DIFFERENT TRANSFORMISTIC THEORIES 293
+
+ The Organic Form and Entelechy 294
+
+ *C.* THE LOGIC OF HISTORY 297
+
+ 1. THE POSSIBLE ASPECTS OF HISTORY 299
+
+ 2. PHYLOGENETIC POSSIBILITIES 304
+
+ 3. THE HISTORY OF MANKIND 306
+
+ Cumulations in Human History 308
+ Human History not an “Evolution” 311
+ The Problem of the “Single” as such 315
+
+ *CONCLUSIONS ABOUT SYSTEMATICS AND HISTORY IN GENERAL* 322
+
+
+
+
+THE PROGRAMME
+
+
+ON LORD GIFFORD’S CONCEPTION OF “SCIENCE”
+
+This is the first time that a biologist has occupied this place; the
+first time that a biologist is to try to carry out the intentions of the
+noble and high-minded man to whom this lectureship owes its foundation.
+
+On such an occasion it seems to be not undesirable to inquire what Lord
+Gifford’s own opinions about natural science may have been, what place
+in the whole scheme of human knowledge he may have attributed to those
+branches of it which have become almost the centre of men’s intellectual
+interest.
+
+And, indeed, on studying Lord Gifford’s bequest with the object of
+finding in it some reference to the natural sciences, one easily notes
+that he has assigned to them a very high place compared with the other
+sciences, at least in one respect: with regard to their methods.
+
+There is a highly interesting passage in his will which leaves no doubt
+about our question. After having formally declared the foundation of
+this lectureship “for Promoting, Advancing, Teaching and Diffusing
+the study of Natural Theology in the widest sense of that term,” and
+after having arranged about the special features of the lectures, he
+continues: “I wish the lecturers to treat their subject as a strictly
+natural science, the greatest of all possible sciences, indeed, in one
+sense, the only science, that of Infinite Being.... I wish it considered
+just as astronomy or chemistry is.”
+
+Of course, it is not possible to understand these words of Lord
+Gifford’s will in a quite literal sense. If, provisionally, we call
+“natural theology” the ultimate conclusions which may be drawn from a
+study of nature in connection with all other results of human sciences,
+there cannot be any doubt that these conclusions will be of a rather
+different character from the results obtained in, say, the special field
+of scientific chemistry. But, nevertheless, there are, I think, two
+points of contact between the wider and the narrower field of knowledge,
+and both of them relate to method. Lord Gifford’s own phrase, “Infinite
+Being,” shows us one of these meeting-points. In opposition to history
+of any form, natural sciences aim at discovering such truths as are
+independent of special time and of special space, such truths as are
+“ideas” in the sense of Plato; and such eternal results, indeed, always
+stand in close relation to the ultimate results of human knowledge
+in general. But besides that there is still another feature which
+may be common both to “natural theology” and to the special natural
+sciences, and which is most fully developed in the latter: freedom from
+prepossessions. This, at least, is an ideal of all natural sciences;
+I may say it is *the* ideal of them. That it was this feature which
+Lord Gifford had in view in his comparison becomes clear when we read
+in his will that the lectures on natural theology are to be delivered
+“without reference to or reliance upon any supposed special exceptional
+or so-called miraculous revelation.”
+
+So we might say that both in their logical and their moral methods,
+natural sciences are to be the prototype of “Natural Theology” in Lord
+Gifford’s sense.
+
+
+NATURAL SCIENCES AND “NATURAL THEOLOGY”
+
+But now let us study in a more systematic manner the possible relations
+of the natural sciences to natural theology as a science.
+
+How is it possible for a natural scientist to contribute to the science
+of the highest and ultimate subject of human knowledge?
+
+Almost all natural sciences have a sort of naïveté in their own spheres;
+they all stand on the ground of what has been called a naïve realism,
+as long as they are, so to say, at home. That in no way prejudices
+their own progress, but it seems to stand in the way of establishing
+contact with any higher form of human knowledge than themselves.
+One may be a first-rate organic chemist even when looking upon the
+atoms as small billiard balls, and one may make brilliant discoveries
+about the behaviour of animals even when regarding them in the most
+anthropomorphic manner--granted that one is a good observer; but it
+can hardly be admitted that our chemist would do much to advance the
+theory of matter, or our biologist to solve the problem of the relations
+between body and mind.
+
+It is only by the aid of philosophy, or I would rather say by keeping
+in constant touch with it, that natural sciences are able to acquire
+any significance for what might be called *the* science of nature in the
+most simple form. Unhappily the term “natural philosophy” is restricted
+in English to theoretical physics. This is not without a high degree of
+justification, for theoretical physics has indeed lost its naïveté and
+become a philosophy of nature; but it nevertheless is very unfortunate
+that this use of the term “natural philosophy” is established in
+this country, as we now have no proper general term descriptive of a
+natural science that is in permanent relation to philosophy, a natural
+science which does not use a single concept without justifying it
+epistemologically, *i.e.* what in German, for instance, would simply be
+called “Naturphilosophie.”
+
+Let us call it philosophy of nature; then we may say that only by
+becoming a true philosophy of nature are natural sciences of all sorts
+able to contribute to the highest questions which man’s spirit of
+inquiry can suggest.
+
+These highest questions themselves are the outcome of the combination
+of the highest results of all branches of philosophy, just as our
+philosophy of nature originated in the discussion of the results of
+all the separate natural sciences. Are those highest questions not
+only to be asked, are they to be also solved? To be solved in a way
+which does not exceed the limits of philosophy as the domain of actual
+understanding?
+
+The beginning of a long series of studies is not the right place to
+decide this important question; and so, for the present certainly,
+“natural theology” must remain a problem. In other words: it must
+remain an open question at the beginning of our studies, whether after
+all there can be any final general answer, free from contradictions,
+applicable to the totality of questions asked by all the branches of
+philosophy.
+
+But let us not be disturbed by this problematic entrance to our studies.
+Let us follow biology on its own path; let us study its transition from
+a “naïve” science to a real branch of the philosophy of nature. In this
+way we perhaps shall be able to understand what its part may be in
+solving what can be solved.
+
+That is to be our subject.
+
+
+OUR PHILOSOPHICAL BASIS
+
+We call *nature* what is given to us in space.
+
+Of course we are not obliged in these lectures to discuss the
+psychological and epistemological problems of space with its three
+dimensions, nor are we obliged to develop a general theory of reality
+and its different aspects. A few epistemological points will be
+considered later at proper times, and always in connection with results
+of theoretical biology.
+
+At present it must suffice to say that our general philosophical point
+of view will be idealistic, in the critical meaning of the word. The
+universe, and within the universe nature, in the sense just defined,
+is my phenomenon. That is what I know. I know nothing more, either
+positively or negatively; that is to say, I do not know that the world
+is *only my* phenomenon, but, on the other hand, I know nothing about
+its “absolute reality.” And more, I am not even able to describe in
+intelligible words what “absolute reality” might mean. I am fully
+entitled to state: the universe *is* as truly as I am--though in
+a somewhat different sense of “being”--and I *am* as truly as the
+universe is; but I am not entitled to state anything beyond these
+two corresponding phrases. You know that, in the history of European
+philosophy at least, Bishop Berkeley was the first clearly to outline
+the field of idealism.
+
+But my phenomenon--the world, especially nature--consists of elements
+of two different kinds: some of them are merely passive, some of them
+contain a peculiar sort of activity in themselves. The first are
+generally called sensations, but perhaps would be better called elements
+or presentations; the others are forms of construction, and, indeed,
+there is an active element embraced in them in this sense, that they
+allow, by their free combination, the discovery of principles which
+are not to be denied, which must be affirmed, whenever their meaning
+is understood. You know that I am speaking here of what are generally
+called categories and synthetic judgments *a priori*, and that it was
+Kant who, on the foundations laid by Locke, Hume, and Leibnitz, first
+gave the outlines of what may be called the real system of critical
+philosophy. Indeed, our method will be to a great extent Kantian, though
+with certain exceptions; it is to be strictly idealistic, and will not
+in the Kantian way operate with things in themselves; and it regards
+the so-called “synthetic judgment *a priori*” and the problem of the
+relation between categorical principles and experience in a somewhat
+different manner. We think it best to define the much disputed concept
+“*a priori*” as “independent of the *amount* of experience”; that is
+to say, all categories and categorical principles are brought to my
+consciousness by that fundamental event which is called experience, and
+therefore are not independent of it, but they are not inferences from
+experience, as are so-called empirical laws. We almost might say that we
+only have to be reminded of those principles by experience, and, indeed,
+we should not, I think, go very far wrong in saying that the Socratic
+doctrine, that all knowledge is recollection, holds good as far as
+categories and categorical principles are in question.
+
+But enough at present about our general philosophy.
+
+As to the philosophy of nature, there can be no doubt that, on the basis
+of principles like those we have shortly sketched, its ultimate aim must
+be to co-ordinate everything in nature with terms and principles of the
+categorical style. The philosophy of nature thus becomes a system; a
+system of which the general type is afforded by the innate constructive
+power of the Ego. In this sense the Kantian dictum remains true, that
+the Ego prescribes its own laws to nature, though, of course, “nature,”
+that is, what is given in space, must be such as to permit that sort of
+“prescription.”
+
+One often hears that all sciences, including the science of sciences,
+philosophy, have to find out what is true. What, then, may be called
+“true” by an idealistic philosopher, for whom the old realistic formula
+of the conformity between knowledge and the object cannot have any
+meaning? Besides its ordinary application to simple facts or to simple
+judgments, where the word truth only means absence of illusion or no
+false statement, truth can be claimed for a philosophical doctrine or
+for a system of such doctrines only in the sense that there are no
+contradictions amongst the parts of the doctrine or of the system
+themselves, and that there are no features in them which impel our
+categorical Ego to further analysis.
+
+Those of you who attended Professor Ward’s lectures on “Naturalism and
+Agnosticism,” or who have read his excellent book on that subject, will
+know what the aims of a theory of matter are. You will also be aware
+that, at present, there does not exist any theory of matter which can
+claim to be “true”; there are contradictions in every theory of matter,
+and, moreover, there are always some points where we are obliged to ask
+for further information and receive no answer. Experience here has not
+yet aroused all the categorical functions which are needed in order to
+form one unity out of what seem to be incompatibilities at the present
+day. Why is that? Maybe because experience is not yet complete in this
+field, but maybe also because the whole subject is so complicated
+that it takes much time to attach categorical functions to what is
+experienced.
+
+But it is not our object here to deal either with epistemology proper
+or with ontology: a full analysis of biological facts is our problem.
+Why, then, all these introductions? why all these philosophical sketches
+in fields of knowledge which have quite another relation to philosophy
+than biology has? Biology, I hear some one say, is simply and solely
+an empirical science; in some sense it is nothing but applied physics
+and chemistry, perhaps applied mechanics. There are no fundamental
+principles in biology which could bring it in any close contact with
+philosophy. Even the one and only principle which might seem to be
+an innate principle of our experience about life, the principle of
+evolution, is only a combination of more simple factors of the physical
+and chemical type.
+
+It will be my essential endeavour to convince you, in the course of
+these lectures, that such an aspect of the science of biology is wrong;
+that biology is an elemental natural science in the true sense of the
+word.
+
+But if biology is an elemental science, then, and only then, it stands
+in close relations to epistemology and ontology--in the same relations
+to them, indeed, as every natural science does which deals with true
+elements of nature, and which is willing to abandon naïve realism and
+contribute its share to the whole of human knowledge.
+
+And, therefore, a philosophical sketch is not out of place at the
+beginning of lectures on the Philosophy of the Organism. We may be
+forced, we, indeed, shall be forced, to remain for some time on the
+ground of realistic empiricism, for biology has to deal with very
+complicated experiences; but there will be a moment in our progress when
+we shall enter the realm of the elemental ontological concepts, and
+in that very moment our study of life will have become a part of real
+philosophy. It was not without good reasons, therefore, that I shortly
+sketched, as a sort of introduction to my lectures, the general point of
+view which we shall take with regard to philosophical questions, and to
+questions of the philosophy of nature in particular.
+
+
+ON CERTAIN CHARACTERISTICS OF BIOLOGY AS A SCIENCE
+
+Biology is the science of life. Practically, all of you know what a
+living being is, and therefore it is not necessary to formulate a
+definition of life, which, at the beginning of our studies, would be
+either provisional and incomplete, or else dogmatic. In some respects,
+indeed, a definition should rather be the end of a science than its
+opening.
+
+We shall study the phenomena of living organisms analytically, by the
+aid of experiment; our principal object will be to find out laws in
+these phenomena; such laws will then be further analysed, and precisely
+at that point we shall leave the realm of natural science proper.
+
+Our science is the highest of all natural sciences, for it embraces as
+its final object the actions of man, at least in so far as actions also
+are phenomena observable on living bodies.
+
+But biology is also the most difficult of all natural sciences, not
+only from the complexity of the phenomena, which it studies, but in
+particular for another reason which is seldom properly emphasised, and
+therefore will well repay us for a few words devoted to it.
+
+Except so far as the “elements” of chemistry come into account, the
+experimenter in the inorganic fields of nature is not hampered by the
+specificity of composite objects: he makes all the combinations he
+wants. He is always able to have at his disposal red rays of a desired
+wave length when and where he wants, or to have, at a given time and
+place, the precise amount of any organic compound which he wishes to
+examine. And he forces electricity and electromagnetism to obey his
+will, at least with regard to space, time, and intensity of their
+appearance.
+
+The biologist is not able to “make” life, as the physicist has made red
+rays or electromagnetism, or as the chemist has made a certain compound
+of carbon. The biologist is almost always in that strange plight in
+which the physicist would be if he always had to go to volcanoes in
+order to study the conductivity of heat, or if he had to wait for
+thunderstorms in order to study electricity. The biologist is dependent
+on the specificity of living objects as they occur in nature.
+
+A few instances may show you what great inconveniences may hence arise
+to impede practical biological research. We later on shall have to deal
+with experiments on very young embryos: parts of the germ will have
+to be destroyed in order to study what will happen with the rest. Now
+almost all germs are surrounded by a membrane; this membrane has to be
+detached before any operation is possible. But what are we to do if it
+is not possible to remove the membrane without killing the embryo? Or
+what if, as for instance in many marine animals, the membrane may be
+removed but the germs are killed by contact with sea-water? In both
+cases no experiments at all will be possible on a sort of germ which
+otherwise, for some special circumstances of its organisation, might
+have given results of importance. These results become impossible for
+only a practical, for a very secondary reason; but enough: they are
+impossible, and they might have thrown light on problems which now
+must remain problems. Quite the same thing may occur in experiments
+on physiology proper or functional physiology: one kind of animals
+survives the operation, the other kind does not, and therefore, for
+merely extrinsic reasons, the investigations have to be restricted to
+the first, though the second might have given more important results.
+And thus the biological experimenter always finds himself in a sort of
+dependence on his subjects, which can hardly be called pleasant. To a
+great extent the comparatively slow advance of biological sciences is
+due to this very fact: the unalterable specific nature of biological
+material.
+
+But there is still another feature of biology dependent on the same
+fact. If a science is tied down to specific objects in every path it
+takes, it first, of course, has to know all about those objects, and
+that requires nothing else but plain description. We now understand why
+pure description, in the most simple sense of the word, takes up such an
+enormous part of every text-book of biological science. It is not only
+morphology, the science of form, that is most actively concerned with
+description; physiology also, in its present state, is pure description
+of what the functions of the different parts of the body of animals and
+plants actually *are*, at least for about nine-tenths of its range. It
+seems to me important to press this point very emphatically, since we
+often hear that physiology is from the very beginning a much higher sort
+of knowledge than morphology, inasmuch as it is rational. That is not at
+all true of the beginning of physiology: what the functions of the liver
+or of the root are has simply to be described just as the organisation
+of the brain or of the leaf, and it makes no difference logically that
+one species of description has to use the experimental method, while the
+other has not. The experiment which only discovers what happens here or
+what happens there, possesses no kind of logical superiority over pure
+description at all.
+
+But there will be another occasion in our lectures to deal more fully
+with the logic of experiment and with the differences of descriptive
+knowledge and real rational science.
+
+
+THE THREE DIFFERENT TYPES OF KNOWLEDGE ABOUT NATURE
+
+Natural sciences cannot originate before the given phenomena of nature
+have been investigated in at least a superficial and provisional manner,
+by and for the practical needs of man. But as soon as true science
+begins in any limited field, dealing, let us say, with animals or with
+minerals, or with the properties of bodies, it at once finds itself
+confronted by two very different kinds of problems, both of them--like
+all “problems”--created in the last resort by the logical organisation
+of the human mind, or, to speak still more correctly, of the Ego.
+
+In any branch of knowledge which practical necessities have separated
+from others, and which science now tries to study methodically, there
+occur general sequences in phenomena, general orders of events. This
+uniformity is revealed only gradually, but as soon as it has shown
+itself, even in the least degree, the investigator seizes upon it. He
+now devotes himself chiefly, or even exclusively, to the generalities in
+the sequences of all changes. He is convinced that there must be a sort
+of most general and at the same time of most universal connection about
+all occurrences. This most universal connection has to be found out; at
+least it will be the ideal that always will accompany the inquiring mind
+during its researches. The “law of nature” is the ideal I am speaking
+about, an ideal which is nothing less than one of the postulates of the
+possibility of science at all.
+
+Using for our purposes a word which has been already introduced into
+terminology by the philosopher Windelband, though in a somewhat
+different sense, we shall call that part of every branch of natural
+sciences which regards the establishment of a law of nature as its
+ideal, “nomothetic,” *i.e.* “law-giving.”
+
+But while every natural science has its nomothetic side, it also has
+another half of a very different kind. This second half of every natural
+science does not care for the same general, the same universal, which
+is shown to us in every event in a different and specified kind: it
+is diversity, it is specification, that constitutes the subject of
+its interest. Its aim is to find a sufficient reason for the types of
+diversities, for the types of specifications. So in chemistry there
+has been found a systematic order in the long series of the compounds
+and of the elements; crystallography also has its different systems of
+crystals, and so on.
+
+We have already employed the word by which we shall designate this
+second half of every natural science: it is the “systematic” side of
+science.
+
+Nomothetic work on the one side and systematics on the other do, in
+fact, appear in every natural science, and besides them there are no
+other main parts. But “science” as a whole stands apart from another
+aspect of reality which is called “history.” History deals with
+particulars, with particular events at such and such a place, whilst
+science always abstracts from the particular, even in its systematic
+half.[1]
+
+[1] Windelband (*Geschichte und Naturwissenschaft*, 3 Auflage, 1904)
+gives the name “nomothetic” to the whole of our “science” and calls the
+method of history “idiographic.” We thought it better to establish three
+fundamental types of all possible branches of knowledge.
+
+
+GENERAL PLAN OF THESE LECTURES
+
+Turning now to a sort of short outline of what is to be discussed
+in the whole of our future lectures, this summer and next, it seems
+clear, without further analysis, that biology as a science has its
+nomothetic and its systematic part also; respiration and assimilation,
+for instance, have proved to be types of natural laws among living
+phenomena, and that there is a “system” of animals and plants is too
+commonly known to require further explanation here. Therefore we might
+study first biological laws, and after that biological systematics, and
+in the third place perhaps biological history. But that would hardly
+correspond to the philosophical aims of our lectures: our chief object
+is not biology as a regular science, as treated in text-books and in
+ordinary university lectures; our chief object is the Philosophy of the
+Organism, as aided and supported by scientific biology. Therefore a
+general acquaintance with biology must be assumed in these lectures, and
+the biological materials must be arranged according to their bearing on
+further, that is on philosophical, analysis.
+
+That will be done, not, of course, to the extent of my regarding every
+one of my audience as a competent biologist; on the contrary, I shall
+explain most fully all points of biology proper, and even of the most
+simple and descriptive kind of biology, which serve as bases for
+philosophical analysis. But I shall do so only if they indeed do serve
+as such bases. All our biology will be not for its own sake, but for the
+sake of philosophy.
+
+Whilst regarding the whole of the biological material with such aims,
+it seems to me best to arrange the properly scientific material which
+is to be the basis of my discussions, not along the lines which biology
+as an independent science would select,[2] but to start from the three
+different kinds of fundamental phenomena which living bodies offer to
+investigation, and to attach all systematics exclusively to one of them.
+For there will not be very much for philosophy to learn from biological
+systematics at present.
+
+[2] See J. Arth. Thomson, *The Science of Life*, London, 1899.
+
+Life is unknown to us except in association with bodies: we only know
+living bodies and call them organisms. It is the final object of all
+biology to tell us what it ultimately means to say that a body is
+“living,” and in what sorts of relation body and life stand one to the
+other.
+
+But at present it is enough to understand the terms “body” and “living”
+in the ordinary and popular sense.
+
+Regarding living bodies in this unpretentious manner, and recollecting
+what the principal characters are of all bodies we know as living ones,
+we easily find that there are three features which are never wanting
+wherever life in bodies occurs. All living bodies are specific as to
+form--they “have” a specific form, as we are accustomed to say. All
+living bodies also exhibit metabolism; that is to say, they stand in a
+relation of interchange of materials with the surrounding medium, they
+take in and give out materials, but their form can remain unchanged
+during these processes. And, in the last place, we can say that all
+living bodies move; though this faculty is more commonly known among
+animals only, even elementary science teaches the student that it also
+belongs to plants.
+
+Therefore we may ask for “laws of nature” in biology about form, about
+metabolism, and about movements. In fact, it is according to this scheme
+that we shall arrange the materials of the biological part of our
+lectures, though, as we cannot regard the three divisions as equally
+important in their bearing on our ultimate purposes, we shall not treat
+them quite on equal terms. It will appear that, at least in the present
+state of science, the problems of organic form and of organic movement
+have come into much closer relation to philosophical analysis than have
+most of the empirical data on metabolism.
+
+It is *form* particularly which can be said to occupy the very centre
+of biological interest; at least it furnishes the foundation of all
+biology. Therefore we shall begin our scientific studies with a full and
+thorough analysis of form. The science of living forms, later on, will
+afford us a key to study metabolism proper with the greatest advantage
+for our philosophical aims, and therefore the physiology of what is
+usually called the vegetative functions will be to us a sort of appendix
+to our chapters on form; only the theory of a problematic “living
+substance” and of assimilation in the most general meaning of the word
+will be reserved for the philosophical part; for very good reasons,
+as I hope to show. But our chapters on the living forms will have yet
+another appendix besides the survey of the physiology of metabolism.
+Biological systematics almost wholly rests on form, on “morphology”; and
+what hitherto has been done on the metabolical side of their problems,
+consists of a few fragments, which are far from being an equivalent to
+the morphological system; though, of course it must be granted that,
+logically, systematics, in our general meaning of the word, as the sum
+of problems about the typically different and the specific, may be
+studied on the basis of each one of the principal characteristics of
+living bodies, not only on that of their forms. Therefore, systematics
+is to be the second appendix to the chief part of our studies in
+morphology, and systematics, in its turn, will later on lead us to
+a short sketch of the historical side of biology, to the theory of
+evolution in its different forms, and to the logic of history in general.
+
+So far will our programme be carried out during this summer. Next year
+the theory of movements will conclude our merely scientific analysis,
+and the remaining part of the course next summer will be devoted to the
+philosophy of living nature. I hope that nobody will be able to accuse
+our philosophy of resting on unsound foundations. But those of you, on
+the other hand, who would be apt to regard our scientific chapters as a
+little too long compared with their philosophical results, may be asked
+to consider that a small clock-tower of a village church is generally
+less pretentious but more durable than the campanile of San Marco has
+been.
+
+Indeed, these lectures will afford more “facts” to my hearers, than
+Gifford Lectures probably have done, as a rule. But how could that
+be otherwise on the part of a naturalist? Scientific facts are the
+material that the philosophy of nature has to work with, but these
+facts, unfortunately, are not as commonly known as historical facts,
+for instance, generally are; and they must be known, in order that a
+philosophy of the organism may be of any value at all, that it may be
+more than a mere entertainment.
+
+Goethe once said, that even in so-called facts there is more “theory”
+than is usually granted; he apparently was thinking of what might be
+called the ultimate or the typical facts in science. It is with such
+typical or ultimate facts, of course, that we must become acquainted if
+our future philosophy is to be of profit to us.
+
+Certainly, there would be nothing to prevent us from arranging our
+materials in a manner exactly the reverse of that which we shall adopt;
+we could begin with a general principle about the organic, and could
+try to deduce all its special features from that principle, and such a
+way perhaps would seem to be the more fascinating method of argument.
+But though logical it would not be psychological, and therefore would
+be rather unnatural. And thus our *most* general principle about the
+organic will not come on the scene before the eighteenth of these twenty
+lectures, although it is not a mere inference or deduction from the
+former lectures: it will be a culmination of the whole, and we shall
+appreciate its value the better the more we know what that whole really
+is.
+
+
+GENERAL CHARACTER OF THE ORGANIC FORM
+
+Our programme of this year, it was said, is to be devoted wholly
+to organic forms, though one of its appendixes, dealing with some
+characteristics of the physiology of metabolism, will lead us on to a
+few other phenomena. What then are the essentials of a living form, as
+commonly understood even without a special study of biology?
+
+Living bodies are not simple geometrical forms, not, like crystals,
+merely a typical arrangement of surfaces in space, to be reduced
+theoretically, perhaps, to an arrangement of molecules. Living bodies
+are typically combined forms; that is to say, they consist of simpler
+parts of different characters, which have a special arrangement with
+regard to one another; these parts have a typical form of their own and
+may again be combinations of more simple different parts. But besides
+that, living bodies have not always the same typically combined form
+during the whole of their life: they become more complicated as they
+grow older; they all begin from one starting point, which has little
+form at all, viz., the egg. So the living form may be called a “genetic
+form,” or a form considered as a process, and therefore *morphogenesis*
+is the proper and adequate term for the science which deals with the
+laws of organic forms in general; or, if you prefer not to use the
+same word both for a science and for the subjects of that science, the
+*physiology of morphogenesis*.
+
+Now there are different branches of the physiology of morphogenesis or
+physiology of form. We may study, and indeed we at first shall study,
+what are the laws of the morphogenetic processes leading from the egg
+to the adult: that may be properly called physiology of development.
+But living forms are not only able to originate in one unchangeable
+way: they may restore themselves, if disturbed, and thus we get the
+physiology of restoration or restitution as a second branch of the
+science of morphogenesis. We shall draw very important data, some of the
+foundations indeed of our philosophical discussions, from the study of
+such restitutions. Besides that, it is to them that our survey of the
+problems of the physiology of metabolism is to be appended.
+
+Living forms not only originate from the egg and are able to restore
+themselves, they also may give origin to other forms, guaranteeing in
+this way the continuity of life. The physiology of heredity therefore
+appears as the counterpart to those branches of the physiology of form
+which deal with individual form and its restitutions. And our discussion
+on heredity may be followed by our second appendix to this chief section
+on form, an appendix regarding the outlines of systematics, evolution
+and history.
+
+Theoretical considerations on biology generally start, or at least,
+used to start, from the evolution theory, discussing all other problems
+of the physiology of form by the way only, as things of secondary
+importance. You see from our programme, that we shall go just the
+opposite way: evolution will come last of all, and will be treated
+shortly; but the morphogenesis of the individual will be treated very
+fully, and very carefully indeed.
+
+Why then this deviation from what is the common practice? Because we do
+not know very much about evolution at all, because in this field we are
+just at the very beginning of what deserves the name of exact knowledge.
+But concerning individual morphogenesis we really know, even at present,
+if not very much, at least something, and that we know in a fairly exact
+form, aided by the results of experiments.
+
+And it will not be without its reward, if we restrict our aims in such a
+manner, if we prefer to deal more fully with a series of problems, which
+may seem at the first glance to be of less interest than others. After a
+few lectures we shall find already that we may decide one very important
+question about life merely by an analysis of individual form production,
+and without any regard to problematic and doubtful parts of biology:
+that we may decide the question, whether “life” is only a combination
+of chemical and physical events, or whether it has its elemental laws,
+laws of its own.
+
+But to prepare the road that is to lead to such results we first have
+to restrict our aims once more, and therefore the next lecture of this
+course, which eventually is to touch almost every concept of philosophy
+proper, will begin with the pure description of the individual
+development of the common sea-urchin.
+
+
+
+
+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
+
+The organism is a specific body, built up by a typical combination
+of specific and different parts. It is implied in the words of this
+definition, that the organism is different, not only from crystals, as
+was mentioned in the last lecture, but also from all combinations of
+crystals, such as those called dendrites and others, which consist of a
+typical arrangement of identical units, the nature of their combination
+depending on the forces of every single one of their parts. For this
+reason dendrites, in spite of the typical features in their combination,
+must be called aggregates; but the organism is not an aggregate even
+from the most superficial point of view.
+
+We have said before, what must have been familiar to you already, that
+the organism is not always the same in its individual life, that it
+has its development, leading from simpler to more complicated forms of
+combination of parts; there is a “production of visible manifoldness”
+carried out during development, to describe the chief character of that
+process in the words of Wilhelm Roux. We leave it an open question in
+our present merely descriptive analysis, whether there was already a
+“manifoldness,” in an invisible state, before development, or whether
+the phrase “production of manifoldness” is to be understood in an
+absolute sense.
+
+It has not always been granted in the history of biology, and of
+embryology especially, that production of visible manifoldness is the
+chief feature of what is called an organism’s embryology or ontogeny:
+the eighteenth century is full of determined scientific battles over the
+question. One school, with Albert von Haller and Bonnet as its leading
+men, maintained the view that there was no production of different parts
+at all in development, this process being a mere “evolutio,” that is,
+a growth of parts already existing from the beginning, yes, from the
+very beginning of life; whilst the other school, with C. F. Wolff and
+Blumenbach at its head, supported the opposite doctrine of so-called
+“epigenesis,” which has been proved to be the right one.
+
+To some extent these differences of opinion were only the outcome of the
+rather imperfect state of the optical instruments of that period. But
+there were also deeper reasons beyond mere difficulties of description;
+there were theoretical convictions underlying them. It is *impossible*,
+said the one party, that there is any real production of new parts;
+there *must* be such a production, said the other.
+
+We ourselves shall have to deal with these questions of the theory of
+organic development; but at present our object is narrower, and merely
+descriptive. It certainly is of great importance to understand most
+clearly that there actually *is* a “production of visible manifoldness”
+during ontogenesis in the descriptive sense; the knowledge of the fact
+of this process must be the very foundation of all studies on the theory
+of development in any case, and therefore we shall devote this whole
+lecture to studies in merely descriptive embryology.
+
+But descriptive embryology, even if it is to serve merely as an
+instance of the universality of the fact of epigenesis, can only be
+studied successfully with reference to a concrete case. We select the
+development of the common sea-urchin (*Echinus microtuberculatus*) as
+such a case, and we are the more entitled to select this organism rather
+than another, because most of the analytical experimental work, carried
+out in the interests of a real theory of development, has been done
+on the germs of this animal. Therefore, to know at least the outlines
+of the individual embryology of the Echinus may indeed be called the
+*conditio sine qua non* for a real understanding of what is to follow.
+
+
+THE CELL[3]
+
+[3] E. B. Wilson, *The Cell in Development and Inheritance*, New York,
+Macmillan, 1896.
+
+You are aware that all organisms consist of organs and that each of
+their organs has a different function: the brain, the liver, the eyes,
+the hands are types of organs in animals, as are the leaves and the
+pistils in plants.
+
+You are also aware that, except in the lowest organisms, the so-called
+Protista, all organs are built up of cells. That is a simple fact of
+observation, and I therefore cannot agree with the common habit of
+giving to this plain fact the title of cell-“theory.” There is nothing
+theoretical in it; and, on the other hand, all attempts to conceive
+the organism as a mere aggregate of cells have proved to be wrong. It
+is *the whole* that uses the cells, as we shall see later on, or that
+may not use them: thus there is nothing like a “cell-theory,” even in a
+deeper meaning of the word.
+
+The cell may have the most different forms: take a cell of the skin, of
+a muscle, of a gland, of the wood in plants as typical examples. But in
+every case two parts may be distinguished in a cell: an outside part,
+the protoplasm, and an inside part, the nucleus, to leave out of special
+account several others, which, by the way, may only be protoplasmatic
+modifications.
+
+Protoplasm is a mere name for what is not the nucleus; in any case it is
+not a homogeneous chemical compound; it consists of many such compounds
+and has a sort of architecture; all organic functions are based upon
+its metabolism. The nucleus has a very typical structure, which stands
+in a close relation to its behaviour during the most characteristic
+morphological period of the cell: during its division. Let us devote a
+few words to a consideration of this division and the part the nucleus
+plays in it; it will directly bear on future theoretical considerations
+about development.
+
+There is a certain substance in every nucleus of a cell which stains
+most markedly, whenever cells are treated with pigments: the name
+of “chromatin” has been given to it. The chromatin always gives the
+reaction of an acid, while protoplasm is basic; besides that it seems to
+be a centre of oxidation. Now, when a division of a cell is to occur,
+the chromatin, which had been diffusely distributed before, in the form
+of small grains, arranges itself into a long and very much twisted
+thread. This thread breaks, as it were by sections, into almost equal
+parts, typical in number for each species, and each of these parts is
+split at full length. A certain number of pairs of small threads, the
+so-called “chromosomes,” are the ultimate result of this process, which
+intentionally has been described a little schematically, the breaking
+and the splitting in fact going on simultaneously or occasionally even
+in reverse order. While what we have described is performing in the
+nucleus, there have happened some typical modifications in protoplasm,
+and then, by an interaction of protoplasmatic and nuclear factors, the
+first step in the actual division of the cell begins. Of each pair of
+the small threads of chromatin one constituent is moved to one side of
+the cell, one to the other; two daughter-nuclei are formed in this way;
+the protoplasm itself at the same time forms a circular furrow between
+them; the furrow gets deeper and deeper; at last it cuts the cell in
+two, and the division of the cell is accomplished.
+
+Not only is the growth of the already typically formed organism carried
+out by a series of cell-divisions, but also development proper in our
+sense, as a “production of visible manifoldness,” is realised to a great
+extent by the aid of such divisions, which therefore may indeed be said
+to be of very fundamental importance (Fig. 1).
+
+[Illustration: Fig. 1.--Diagram of Cell-Division (*after* Boveri).
+
+*a.* Resting cell; the chromatin distributed in the form of small
+granules inside the nucleus. Outside the nucleus is the “centrosome,”
+not mentioned in the text.
+
+*b.* Beginning of division; the chromatin arranged in the form of a long
+thread. Centrosome divided in two.
+
+*c.* The thread of chromatin cut into four parts, the “chromosomes.”
+
+*d.* The four parts of the chromatin arranged symmetrically between the
+centrosomes and the star-like “spheres.”
+
+*e.* Each of the chromosomes split at full length.
+
+*f.* Beginning of division of protoplasm; the two parts of each
+chromosome separated.
+
+*g.* End of cell-division.]
+
+Each cell-division which promotes growth is followed by the
+enlargement of the two daughter-cells which result from it; these two
+daughter-elements attain the exact size of the mother-cell before
+division, and as soon as this size is reached a new division begins:
+so the growth of the whole is in the main the result of the growth of
+the elements. Cell-divisions during real organ-formation may behave
+differently, as will be described at a proper occasion.
+
+
+THE EGG: ITS MATURATION AND FERTILISATION
+
+We know that all the organs of an animal or plant consist of cells, and
+we know what acts a cell can perform. Now there is one very important
+organ in all living beings, which is devoted to reproduction. This
+organ, the so-called ovary in animals, is also built up of cells,
+and its single cells are called the eggs; the eggs originated by
+cell-division, and cell-division is to lead from them to the new adult.
+
+But, with a very few exceptions, the egg in the ovary is not able to
+accomplish its functions, unless certain typical events have occurred,
+some of which are of a merely preparatory kind, whilst the others are
+the actual stimulus for development.
+
+The preparatory ones are generally known under the name of “maturation.”
+The egg must be “mature,” in order that it may begin development, or
+even that it may be stimulated to it. Maturation consists of a rather
+complicated series of phenomena: later on we shall have occasion to
+mention, at least shortly, what happens in the protoplasm during its
+course; as to the nuclear changes during maturation it may be enough
+for our purposes to say, that there occur certain processes among the
+chromosomes, which lead to an extension of half of them in the form
+of two very small cells, the “directive cells” or “directive or polar
+bodies,” as they have been somewhat cautiously called.
+
+The ripe or mature egg is capable of being fertilised.
+
+Before turning to this important fact, which, by the way, will bring us
+to our specially chosen type, the Echinus, a few words may be devoted to
+the phenomenon of “parthenogenesis,” that is to say, the possibility
+of development without fertilisation, since owing to the brilliant
+discoveries of the American physiologist, Jacques Loeb, this topic forms
+one of the centres of biological interest at present. It has long been
+known that the eggs of certain bees, lice, crayfishes, and other animals
+and also plants, are capable of development without fertilisation at
+all. Now Richard Hertwig and T. H. Morgan already had shown, that at
+least nuclear division may occur in the eggs of other forms--in the egg
+of the sea-urchin for instance--when these eggs are exposed to some
+chemical injuries. But Loeb[4] succeeded in obtaining a full development
+by treating the eggs of echinoderms with chloride of magnesium; thus
+artificial parthenogenesis had been discovered. Later researches have
+shown that artificial parthenogenesis may occur in all classes of the
+animal kingdom and may be provoked by all sorts of chemical or physical
+means. We do not know at present in what the proper stimulus consists
+that must be supposed here to take the place of fertilisation; it seems,
+of course, highly probable that it is always the same in the last
+resort.[5]
+
+[4] *Amer. Journ. Physiol.* vols. iii. and iv. 1900.
+
+[5] According to Delage (*Arch. Zool. exp.*, 3 sér. 10, 1902), it is
+indifferent for the realisation of artificial parthenogenesis, whether
+but one, or both, or neither of the “polar bodies” has been formed. But
+the egg must be in the first stages of maturation to the extent that the
+“nuclear membrane” must be already dissolved.
+
+But enough about processes, which at present are of a highly scientific,
+but hardly of any philosophic interest.
+
+By fertilisation proper we understand the joining of the male element,
+the spermatozoon or the spermia, with the female element, the egg. Like
+the egg, the spermatozoon is but a cell, though the two differ very much
+from one another in the relation between their protoplasm and nucleus:
+in all eggs it is the protoplasm which is comparatively very large, if
+held together with somatic cells, in the spermatozoon it is the nucleus.
+A large amount of reserve material, destined for the growth of the
+future being, is the chief cause of the size of the egg-protoplasm. The
+egg is quite or almost devoid of the faculty of movement, while on the
+contrary, movement is the most typical feature of the spermia. Its whole
+organisation is adapted to movement in the most characteristic manner:
+indeed, most spermatozoa resemble a swimming infusorium, of the type
+of Flagellata, a so-called head and a moving tail are their two chief
+constituents; the head is formed almost entirely of nuclear substance.
+
+It seems that in most cases the spermatozoa swim around at random and
+that their union with the eggs is assured only by their enormous number;
+only in a few cases in plants have there been discovered special stimuli
+of a chemical nature, which attract the spermia to the egg.
+
+But we cannot enter here more fully into the physiology of
+fertilisation, and shall only remark that its real significance is by no
+means clear.[6]
+
+[6] The older theories, attributing to fertilisation (or to
+“conjugation,” *i.e.* its equivalent in Protozoa), some sort of
+“renovation” or “rejuvenescence” of the race, have been almost
+completely given up. (See Calkins, *Arch. für Entwickelungsmechanik*,
+xv. 1902). R. Hertwig recently has advocated the view, that abnormal
+relations between the amounts of nuclear and of protoplasmatic material
+are rectified in some way by those processes. Teleologically, sexual
+reproduction has been considered as a means of variability (Weismann),
+but also as a means of preserving the type!
+
+
+THE FIRST DEVELOPMENT PROCESS OF ECHINUS
+
+Turning now definitively to the special kind of organism, chosen of our
+type, the common sea-urchin, we properly begin with a few words about
+the absolute size of its eggs and spermatozoa. All of you are familiar
+with the eggs of birds and possibly of frogs; these are abnormally
+large eggs, on account of the very high amount of reserve material they
+contain. The almost spherical egg of our Echinus only measures about a
+tenth of a millimetre in diameter; and the head of the spermatozoon has
+a volume which is only the four-hundred-thousandth part of the volume
+of the egg! The egg is about on the extreme limit of what can be seen
+without optical instruments; it is visible as a small white point. But
+the number of eggs produced by a single female is enormous and may
+amount to hundreds of thousands; this is one of the properties which
+render the eggs of Echinus so very suitable for experimental research;
+you can obtain them whenever and in any quantity you like; and,
+moreover, they happen to be very clear and transparent, even in later
+stages, and to bear all kinds of operations well.
+
+The spermia enters the egg, and it does so in the open water--another
+of the experimental advantages of our type. Only one spermia enters
+the egg in normal cases, and only its head goes in, the tail is left
+outside. The moment that the head has penetrated the protoplasm of the
+egg a thin membrane is formed by the latter. This membrane is very soft
+at first, becoming much stronger later on; it is very important for all
+experimental work, that by shaking the egg in the first minutes of its
+existence the membrane can easily be destroyed without any damage to the
+egg itself.
+
+And now occurs the chief phenomenon of fertilisation: the nucleus of
+the spermatozoon unites with the nucleus of the egg. When speaking of
+maturation, we mentioned that half of the chromatin was thrown out of
+the egg by that process: now this half is brought in again, but comes
+from another individual.
+
+It is from this phenomenon of nuclear union as the main character of
+fertilisation that almost all theories of heredity assume their right to
+regard the nuclei of the sexual cells as the true “seat” of inheritance.
+Later on we shall have occasion to discuss this hypothesis from the
+point of view of logic and fact.
+
+After the complete union of what are called the male and the female
+“pronuclei,” the egg begins its development; and this development, in
+its first steps, is simply pure cell-division. We know already the chief
+points of this process, and need only add to what has been described,
+that in the whole first series of the cell-divisions of the egg, or,
+to use the technical term, in the whole process of the “cleavage” or
+“segmentation” of it, there is never any growth of the daughter-elements
+after each division, such as we know to occur after all cell-divisions
+of later embryological stages. So it happens, that during cleavage the
+embryonic cells become smaller and smaller, until a certain limit is
+reached; the sum of the volumes of all the cleavage cells together is
+equal to the volume of the egg.
+
+But our future studies will require a more thorough knowledge of the
+cleavage of our Echinus; the experimental data we shall have to describe
+later on could hardly be properly understood without such knowledge.
+The first division plane, or, as we shall say, the first cleavage
+plane, divides the eggs into equal parts; the second lies at right
+angles to the first and again divides equally: we now have a ring of
+four cells. The third cleavage plane stands at right angles to the
+first two; it may be called an equatorial plane, if we compare the egg
+with a globe; it also divides equally, and so we now find two rings,
+each consisting of four cells, and one above the other. But now the
+cell-divisions cease to be equal, at least in one part of the egg: the
+next division, which leads from the eight- to the sixteen-cell stage of
+cleavage, forms four rings, of four cells each, out of the two rings of
+the eight-cell stage. Only in one half of the germ, in which we shall
+call the upper one, or which we might call, in comparison with a globe,
+the northern hemisphere, are cells of equal size to be found; in the
+lower half of the egg four very small cells have been formed at one
+“pole” of the whole germ. We call these cells the “micromeres,” that
+is, the “small parts,” on the analogy of the term “blastomeres,” that
+is, parts of the germ, which is applied to all the cleavage cells in
+general. The place occupied by the micromeres is of great importance
+to the germ as a whole: the first formation of real organs will start
+from this point later on. It is sufficient thus fully to have studied
+the cleavage of our Echinus up to this stage: the later cleavage stages
+may be mentioned more shortly. All the following divisions are into
+equal parts; there are no other micromeres formed, though, of course,
+the cells derived from the micromeres of the sixteen-cell stage always
+remain smaller than the rest. All the divisions are tangential; radial
+cleavages never occur, and therefore the process of cleavage ends at
+last in the formation of one layer of cells, which forms the surface
+of a sphere; it is especially by the rounding-up of each blastomere,
+after its individual appearance, that this real surface layer of cells
+is formed, but, of course, the condition, that no radial divisions
+occur, is the most important one in its formation. When 808 blastomeres
+have come into existence the process of cleavage is finished; a sphere
+with a wall of cells and an empty interior is the result. That only 808
+cells are formed, and not, as might be expected, 1024, is due to the
+fact that the micromeres divide less often than the other elements; but
+speaking roughly, of course, we may say that there are ten steps of
+cleavage-divisions in our form; 1024 being equal to 2^{10}.
+
+We have learned that the first process of development, the cleavage, is
+carried out by simple cell-division. A few cases are known, in which
+cell-division during cleavage is accompanied by a specific migration of
+parts of the protoplasm in the interior of the blastomeres, especially
+in the first two or first four; but in almost all instances cleavage
+is as simple a process of mere division as it is in our sea-urchin.
+Now the second step in development, at least in our form, is a typical
+histological performance: it gives a new histological feature to all
+of the blastomeres: they acquire small cilia on their outer side and
+with these cilia the young germ is able to swim about after it has left
+its membrane. The germ may be called a “blastula” at this stage, as it
+was first called by Haeckel, whose useful denominations of the first
+embryonic stages may conveniently be applied, even if one does not agree
+with most, or perhaps almost all, of his speculations (Fig. 2).
+
+[Illustration: Fig. 2.--Early Development of Echinus, the Common
+Sea-urchin.
+
+*a.* Two cells.
+
+*b.* Four cells.
+
+*c.* Eight cells, arranged in two rings of four, above one another.
+
+*d.* Sixteen cells, four “micromeres” formed at the “vegetative” pole.
+
+*e.* Optical section of the “blastula,” a hollow sphere consisting of
+about one thousand cells, each of them with a small cilium.]
+
+It is important to notice that the formation of the “blastula” from the
+last cleavage stage is certainly a process of organisation, and may also
+be called a differentiation with regard to that stage. But there is in
+the blastula no trace of one *part* of the germ becoming different with
+respect to others of its parts. If development were to go on in this
+direction alone, high organisatory complications might occur: but there
+would always be only one sort of cells, arranged in a sphere; there
+would be only one kind of what is called “tissue.”
+
+But in fact development very soon loads to true differences of the
+parts of the germ with respect to one another, and the next step of the
+process will enable us to apply different denominations to the different
+parts of the embryo.
+
+At one pole of the swimming blastula, exactly at the point where the
+descendants of the micromeres are situated, about fifty cells lose
+contact with their neighbours and leave the surface of the globe, being
+driven into the interior space of it. Not very much is known about the
+exact manner in which these changes of cellular arrangement are carried
+out, whether the cells are passively pressed by their neighbours, or
+whether, perhaps, in a more active manner, they change their surface
+conditions; therefore, as in most ontogenetic processes, the description
+had best be made cautiously in fairly neutral or figurative words.
+
+The cells which in the above manner have entered the interior of the
+blastula are to be the foundation of important parts of the future
+organism; they are to form its connective tissue, many of its muscles,
+and the skeleton. “Mesenchyme,” *i.e.* “what has been infused into the
+other parts,” is the technical name usually applied to these cells.
+We now have to learn their definite arrangement. At first they lie
+as a sort of heap inside the cell wall of the blastula, inside the
+“blastoderm,” *i.e.* skin of the germ. But soon they move from one
+another, to form a ring round the pole at which they entered, and on
+this ring a process takes place which has a very important bearing upon
+the whole type of the organisation of the germ. You will have noticed
+that hitherto the germ with regard to its symmetry has been a monaxial
+or radial formation; the cleavage stages and the blastula with its
+mesenchyme were forms with two different poles, lying at the ends of one
+single line, and round this line everything was arranged concentrically.
+But now what is called “bilateral symmetry” is established; the
+mesenchyme ring assumes a structure which can be symmetrically divided
+only by one plane, but divided in such a way, that one-half of it is the
+mirror image of the other. A figure shows best what has occurred, and
+you will notice (Fig. 3) two masses of cells in this figure, which have
+the forms of spherical triangles: it is in the midst of these triangles
+that the skeleton of the larva *originates*. The germ had an upper and
+a lower side before: it now has got an upper and lower, front and back,
+*right and left* half; it now has acquired that symmetry of organisation
+which our own body has; at least it has got it as far as its mesenchyme
+is concerned.
+
+[Illustration: Fig. 3.--Formation of Mesenchyme in Echinus.
+
+*a.* Outlines of blastula, side-view; mesenchyme forms a heap of cells
+at the “vegetative” pole.
+
+*a*_1. Heap of mesenchyme-cells from above.
+
+*b.* Mesenchyme-cells arranged in a ring round the vegetative pole.
+
+*c.* Mesenchyme-cells arranged in a bilateral-symmetrical figure;
+primordia of skeleton in the midst of two spherical triangles.]
+
+We leave the mesenchyme for a while and study another kind of
+organogenesis. At the very same pole of the germ where the mesenchyme
+cells originated there is a long and narrow tube of cell growing in,
+and this tube, getting longer and longer, after a few hours of growth
+touches the opposite pole of the larva. The growth of this cellular tube
+marks the beginning of the formation of the intestine, with all that
+is to be derived from it. The larva now is no longer a blastula, but
+receives the name of “gastrula” in Haeckel’s terminology; it is built
+up of the three “germ-layers” in this stage. The remaining part of the
+blastoderm is called “ectoderm,” or outer layer; the newly-formed tube,
+“endoderm,” or inner layer; while the third layer is the “mesenchyme”
+already known to us.
+
+The endoderm itself is a radial structure at first, as was the whole
+germ in a former stage, but soon its free end bends and moves against
+one of the sides of the ectoderm, against that side of it where the two
+triangles of the mesenchyme are to be found also. Thus the endoderm
+has acquired bilateral symmetry just as the mesenchyme before, and
+as in this stage the ectoderm also assumes a bilateral symmetry
+in its form, corresponding with the symmetrical relations in the
+endoderm and the mesenchyme, we now may call the whole of our larva a
+bilateral-symmetrical organisation.
+
+It cannot be our task to follow all the points of organogenesis of
+Echinus in detail. It must suffice to state briefly that ere long a
+second portion of the mesenchyme is formed in the larva, starting from
+the free end of its intestine tube; that the formation of the so-called
+“coelum” occurs by a sort of splitting off from this same original
+organ; and that the intestine itself is divided into three parts of
+different size and aspect by two circular sections.
+
+But we must not, I think, dismiss the formation of the skeleton so
+quickly. I told you already that the skeleton has its first origin in
+the midst of the two triangular cell-masses of the mesenchyme; but what
+are the steps before it attains its typical and complicated structure?
+At the beginning a very small tetrahedron, consisting of carbonate of
+calcium, is formed in each of the triangles; the four edges of the
+tetrahedron are produced into thin rods, and by means of a different
+organogenesis along each of these rods the typical formation of the
+skeleton proceeds. But the manner in which it is carried out is very
+strange and peculiar. About thirty of the mesenchyme cells are occupied
+in the formation of skeleton substance on each side of the larva. They
+wander through the interior space of the gastrula--which at this stage
+is not filled with sea water but with a sort of gelatinous material--and
+wander in such a manner that they always come to the right places, where
+a part of the skeleton is to be formed; they form it by a process of
+secretion, quite unknown in detail; one of them forms one part, one the
+other, but what they form altogether, is one whole.
+
+When the formation of the skeleton is accomplished, the typical larva
+of our Echinus is built up; it is called the “pluteus” (Fig. 4). Though
+it is far from being the perfect adult animal, it has an independent
+life of its own; it feeds and moves about and does not go through any
+important changes of form for weeks. But after a certain period of
+this species of independent life as a “larva,” the changes of form it
+undergoes again are most fundamental: it must be transformed into the
+adult sea-urchin, as all of you know. There are hundreds and hundreds
+of single operations of organogenesis to be accomplished before that
+end is reached; and perhaps the strangest of all these operations is a
+certain sort of growth, by which the symmetry of the animal, at least
+in certain of its parts--not in all of them--is changed again from
+bilateral to radial, just the opposite of what happened in the very
+early stages.
+
+[Illustration: Fig. 4.--Larval Development of Echinus.
+
+*A.* The gastrula.
+
+*B.* Later stage, bilateral-symmetrical. Intestine begins to divide
+into three parts.
+
+*C.* Pluteus larva. S = Skeleton. I = Intestine.]
+
+But we cannot follow the embryology of our Echinus further here; and
+indeed we are the less obliged to do so, since in all our experimental
+work we shall have to deal with it only as far as to the pluteus larva.
+It is impossible under ordinary conditions to rear the germs up to the
+adult stages in captivity.
+
+You now, I hope, will have a general idea at least of the processes
+of which the individual development of an animal consists. Of course
+the specific features leading from the egg to the adult are different
+in each specific case, and, in order to make this point as clear as
+possible, I shall now add to our description a few words about what may
+be called a comparative descriptive embryology.
+
+
+COMPARATIVE EMBRYOLOGY
+
+Even the cleavage may present rather different aspects. There may be a
+compact blastula, not one surrounded by only one layer of cells as in
+Echinus; or bilaterality may be established as early as the cleavage
+stage--as in many worms and in ascidians--and not so late as in Echinus.
+The formation of the germ layers may go on in a different order and
+under very different conditions: a rather close relative of our Echinus,
+for instance, the starfish, forms first the endoderm and afterwards
+the mesenchyme. In many cases there is no tube of cells forming the
+“endoderm,” but a flat layer of cells is the first foundation of all the
+intestinal organs: so it is in all birds and in the cuttlefish. And,
+as all of you know, of course, there are very many animal forms which
+have no proper “larval” stage: there is one in the frog, the well-known
+“tadpole,” but the birds and mammals have no larvae; that is to say,
+there is no special stage in the ontogeny of these forms which leads an
+independent life for a certain time, as if it were a species by itself,
+but all the ontogenetical stages are properly “embryonic”--the germ is
+always an “embryo” until it becomes the perfect young organism. And you
+also know that not all skeletons consist of carbonate of calcium, but,
+that there are skeletons of silicates, as in Radiolaria, and of horny
+substance, as in many sponges. And, indeed, if we were to glance at the
+development of plants also, the differences would seem to us probably
+so great that all the similarities would seem to disappear.
+
+But there are similarities, nevertheless, in all development, and we
+shall now proceed to examine what they are. As a matter of fact, it was
+especially for their sake that we studied the ontogeny of a special
+form in such detail; one always sees generalities better if one knows
+the specific features of at least one case. What then are the features
+of most general and far-reaching importance, which may be abstracted
+from the individual history of our sea-urchin, checked always by the
+teachings of other ontogenies, including those of plants?
+
+
+THE FIRST STEPS OF ANALYTICAL MORPHOGENESIS
+
+If we look back upon the long fight of the schools of embryologists in
+the eighteenth century about the question whether individual development
+was to be regarded as a real production of visible manifoldness or as
+a simple growth of visibly pre-existing manifoldness, whether it was
+“epigenesis” or “evolutio,” there can be no doubt, if we rely on all
+the investigations of the last hundred and fifty years, that, taken in
+the descriptive sense, the theory of epigenesis is right. Descriptively
+speaking there *is* a production of visible manifoldness in the course
+of embryology: that is our first and main result. Any one possessed of
+an average microscope may any day convince himself personally that it is
+true.
+
+In fact, true epigenesis, in the descriptive sense of the term, does
+exist. One thing is formed “after” the other; there is not a mere
+“unfolding” of what existed already, though in a smaller form; there is
+no “evolutio” in the old meaning of the word.
+
+The word “evolution” in English usually serves to denote the theory of
+descent, that is of a real relationship of all organisms. Of course we
+are not thinking here of this modern and specifically English meaning of
+the Latin word *evolutio*. In its ancient sense it means to a certain
+degree just the opposite; it says that there is no formation of anything
+new, no transformation, but simply growth, and this is promoted not for
+the race but for the individual. Keeping well in mind these historical
+differences in the meaning of the word “evolutio,” no mistakes, it seems
+to me, can occur from its use. We now shall try to obtain a few more
+particular results from our descriptive study of morphogenesis, which
+are nevertheless of a general bearing, being real characteristics of
+organic individual development, and which, though not calculated of
+themselves to further the problem, will in any case serve to prepare for
+a more profound study of it.
+
+The totality of the line of morphogenetic facts can easily be resolved
+into a great number of distinct processes. We propose to call these
+“elementary morphogenetic processes”; the turning in of the endoderm
+and its division into three typical parts are examples of them. If we
+give the name “elementary organs” to the distinct parts of every stage
+of ontogeny which are uniform in themselves and are each the result of
+one elementary process in our sense, we are entitled to say that each
+embryological stage consists of a certain number of elementary organs.
+The mesenchyme ring, the coelum, the middle-intestine, are instances of
+such organs. It is important to notice well that the word elementary is
+always understood here with regard to visible morphogenesis proper and
+does not apply to what may be called elementary in the physiological
+sense. An elementary process in our sense is a very distinct act of
+form-building, and an elementary organ is the result of every one of
+such acts.
+
+The elementary organs are typical with regard to their position and with
+regard to their histological properties. In many cases they are of a
+very clearly different histological type, as for instance, the cells of
+the three so-called germ-layers; and in other cases, though apparently
+almost identical histologically, they can be proved to be different
+by their different power of resisting injuries or by other means. But
+there are not as many different types of histological structure as there
+are typically placed organs: on the contrary there are many elementary
+organs of the same type in different typical parts of the organism, as
+all of you know to be the case with nerves and muscles. It will not be
+without importance for our future theory of development, carefully to
+notice this fact, that specialisation in the *position* of embryonic
+parts is more strict than in their histology.
+
+But elementary organs are not only typical in position and histology,
+they are typical also with regard to their form and their relative size.
+It agrees with what has been said about histology being independent of
+typical position, that there may be a number of organs in an embryonic
+stage, all in their most typical positions, which though all possessing
+the same histology, may have different forms or different sizes or
+both: the single bones of the skeleton of vertebrates or of adult
+echinoderms are the very best instances of this most important feature
+of organogenesis. If we look back from elementary organs to elementary
+processes, the specialisation of the size of those organs may also be
+said to be the consequence of a typical duration of the elementary
+morphogenetic process leading to them.[7]
+
+[7] The phrase “*ceteris paribus*” has to be added of course, as the
+duration of each single elementary morphogenetic process is liable to
+vary with the temperature and many other conditions of the medium.
+
+I hardly need to say, that the histology, form, and size of elementary
+organs are equally an expression of their present or future
+physiological function. At least they prepare for this function by a
+specific sort of metabolism which sets in very early.
+
+The whole sequence of individual morphogenesis has been divided by some
+embryologists into two different periods; there is a first period,
+during which the foundations of the organisation of the “type” are
+laid down, and a second period, during which the histo-physiological
+specifications are modelled out (von Baer, Götte, Roux). Such a
+discrimination is certainly justified, if not taken too strictly; but
+its practical application would encounter certain difficulties in many
+larval forms, and also, of course, in all plants.
+
+Our mention of plants leads us to the last of our analytical results. If
+an animal germ proceeds in its development from a stage *d* to the stage
+*g*, passing through *e* and *f*, we may say that the whole of *d* has
+become the whole of *f*, but we cannot say that there is a certain part
+of *f* which is *d*, we cannot say that *f* is *d* + *a*. But in plants
+we can: the stage *f* is indeed equal to *a* + *b* + *c* + *d* + *e* +
+*a* [Transcriber’s note: probable typo for *f*] in vegetable organisms;
+all earlier stages are actually visible as parts of the last one. The
+great embryologist, Carl Ernst von Baer, most clearly appreciated these
+analytical differences between animal and vegetable morphogenesis. They
+become a little less marked if we remember that plants, in a certain
+respect, are not simple individuals but colonies, and that among the
+corals, hydroids, bryozoa, and ascidia, we find analogies to plants in
+the animal kingdom; but nevertheless the differences we have stated are
+not extinguished by such reasoning. It seems almost wholly due to the
+occurrence of so many foldings and bendings and migrations of cells and
+complexes of cells in animal morphogenesis, that an earlier stage of
+their development seems *lost* in the later one; those processes are
+almost entirely wanting in plants, even if we study their very first
+ontogenetic stages. If we say that almost all production of surfaces
+goes on outside in plants, inside in animals, we shall have adequately
+described the difference. And this feature again leads to the further
+diversity between animals and plants which is best expressed by calling
+the former “closed,” the latter “open” forms: animals reach a point
+where they are finished, plants never are finished, at least in most
+cases.
+
+I hope you will allow that I have tried to draw from descriptive and
+comparative embryology as many general analytical results as are
+possibly to be obtained. It is not my fault if there are not any
+more, nor is it my fault if the results reached are not of the most
+satisfactory character. You may say that these results perhaps enable
+you to see a little more clearly and markedly than before a few of the
+characters of development, but that you have not really learnt anything
+new. Your disappointment--my own disappointment--in our analysis is due
+to the use of pure description and comparison as scientific methods.
+
+
+THE LIMITS OF PURE DESCRIPTION IN SCIENCE
+
+We have analysed our descriptions as far as we could, and now we must
+confess that what we have found cannot be the last thing knowable
+about individual morphogenesis. There must be something deeper to be
+discovered: we only have been on the surface of the phenomena, we
+now want to get to the very bottom of them. Why then occurs all that
+folding, and bending, and histogenesis, and all the other processes we
+have described? There must be something that drives them out, so to say.
+
+There is a very famous dictum in the *Treatise on Mechanics* by the
+late Gustav Kirchhoff, that it is the task of mechanics to describe
+completely and in the most simple manner all the motions that occur in
+nature. These words, which may appear problematic even in mechanics,
+have had a really pernicious influence on biology. People were extremely
+pleased with them. “‘Describing’--that is just what we always have
+done,” they said; “now we see that we have done just what was right;
+a famous physicist has told us so.” They did not see that Kirchhoff
+had added the words “completely and in the most simple manner”; and
+moreover, they did not consider that Kirchhoff never regarded it as the
+ultimate aim of physics to describe thunderstorms or volcanic eruptions
+or denudations; yet it only is with such “descriptions” that biological
+descriptions of *given* bodies and processes are to be compared!
+
+Physicists always have used both experiment and hypothetical
+construction--Kirchhoff himself did so in the most gifted manner. With
+these aids they have gone through the whole of the phenomena, and what
+they found to be ultimate and truly elemental, that alone may they
+be said to have “described”; but they have “explained” by the aid of
+elementalities what proved to be not elemental in itself.[8]
+
+[8] We shall not avoid in these lectures the word “explain”--so much
+out of fashion nowadays. To “explain” means to subsume under known
+concepts, or rules, or laws, or principles, whether the laws or concepts
+themselves be “explained” or not. Explaining, therefore, is always
+relative: what is elemental, of course, is only to be described, or
+rather to be stated.
+
+It is the *method* of the physicists--not their results--that
+morphogenesis has to apply in order to make progress; and this method
+we shall begin to apply in our next lectures. Physiology proper has
+never been so short-sighted and self-satisfied as not to learn from
+other sciences, from which indeed there was very much to be learned; but
+morphology has: the bare describing and comparing of descriptions has
+been its only aim for about forty years or more, and lines of descent of
+a very problematic character were its only general results. It was not
+seen that science had to begin, not with problematic events of the past,
+but with what actually happens before our eyes.
+
+But before saying any more about the exact rational and experimental
+method in morphology, which indeed may be regarded as a new method,
+since its prevalence in the eighteenth century had been really
+forgotten, we first shall have to analyse shortly some general attempts
+to understand morphogenesis by means of hypothetic construction
+exclusively. Such attempts have become very important as points of
+issue for really exact research, and, moreover, they deserve attention,
+because they prove that their authors at least had not quite forgotten
+that there were still other problems to be solved in morphology than
+only phylogenetical ones.
+
+
+
+
+*B.* EXPERIMENTAL AND THEORETICAL MORPHOGENESIS
+
+1. THE FOUNDATIONS OF THE PHYSIOLOGY OF DEVELOPMENT. “EVOLUTIO” AND
+“EPIGENESIS”
+
+
+THE THEORY OF WEISMANN
+
+Of all the purely hypothetic theories on morphogenesis that of August
+Weismann[9] can claim to have had the greatest influence, and to
+be at the same time the most logical and the most elaborated. The
+“germ-plasma” theory of the German author is generally considered as
+being a theory of heredity, and that is true inasmuch as problems of
+inheritance proper have been the starting-point of all his hypothetic
+speculations, and also form in some respect the most valuable part
+of them. But, rightly understood, Weismann’s theory consists of two
+independent parts, which relate to morphogenesis and to heredity
+separately, and it is only the first which we shall have to take into
+consideration at present; what is generally known as the doctrine of the
+“continuity of the germ-plasm” will be discussed in a later chapter.
+
+[9] *Das Keimplasma*, Jena, 1892.
+
+Weismann assumes that a very complicated organised structure, below
+the limits of visibility even with the highest optical powers, is the
+foundation of all morphogenetic processes, in such a way that, whilst
+part of this structure is handed over from generation to generation as
+the basis of heredity, another part of it is disintegrated during the
+individual development, and directs development by being disintegrated.
+The expression, “part” of the structure, first calls for some
+explanation. Weismann supposes several examples, several copies, as it
+were, of his structure to be present in the germ cells, and it is to
+these copies that the word “part” has been applied by us: at least one
+copy has to be disintegrated during ontogeny.
+
+The morphogenetic structure is assumed to be present in the nucleus
+of the germ cells, and Weismann supposes the disintegration of his
+hypothetic structure to be accomplished by nuclear division. By the
+cleavage of the egg, the most *fundamental* parts of it are separated
+one from the other. The word “fundamental” must be understood as
+applying not to proper elements or complexes of elements of the
+organisation, but to the chief relations of symmetry; the first
+cleavage, for instance, may separate the right and the left part of
+the structure, the second one its upper and lower parts, and after the
+third or equatorial cleavage all the principal eighths of our minute
+organisation are divided off: for the minute organisation, it must now
+be added, had been supposed to be built up differently in the three
+directions of space, just as the adult organism is. Weismann concedes it
+to be absolutely unknown in what manner the proper relation between the
+parts of the disintegrated fundamental morphogenetic structure and the
+real processes of morphogenesis is realised; enough that there may be
+imagined such a relation.
+
+At the end of organogenesis the structure is assumed to have been
+broken up into its elements, and these elements, which may be chemical
+compounds, determine the fate of the single cells of the adult organism.
+
+Here let us pause for a moment. There cannot be any doubt that
+Weismann’s theory resembles to a very high degree the old “evolutio”
+doctrines of the eighteenth century, except that it is a little less
+crude. The chick itself is not supposed to be present in the hen’s egg
+before development, and ontogeny is not regarded as a mere growth of
+that chick in miniature, but what really is supposed to be present in
+the egg is nevertheless a something that in all its parts corresponds
+to all the parts of the chick, only under a somewhat different
+aspect, while all the relations of the parts of the one correspond
+to the relations of the parts of the other. Indeed, only on such an
+hypothesis of a fairly fixed and rigid relation between the parts of
+the morphogenetic structure could it be possible for the disintegration
+of the structure to go on, not by parts of organisation, but by parts
+of symmetry; which, indeed, is a very strange, but not an illogical,
+feature of Weismann’s doctrine.
+
+Weismann is absolutely convinced that there must be a theory of
+“evolutio,” in the old sense of the word, to account for the ontogenetic
+facts; that “epigenesis” has its place only in descriptive embryology,
+where, indeed, as we know, manifoldness in the *visible* sense is
+produced, but that epigenesis can never form the foundation of a real
+morphogenetic *theory*: theoretically one pre-existing manifoldness is
+transformed into the other. An epigenetic theory would lead right beyond
+natural science, Weismann thinks, as in fact, all such theories, if
+fully worked out, have carried their authors to vitalistic views. But
+vitalism is regarded by him as dethroned for ever.
+
+Under these circumstances we have a good right, it seems to me, to speak
+of a *dogmatic* basis of Weismann’s theory of development.
+
+But to complete the outlines of the theory itself: Weismann was
+well aware that there were some grave difficulties attaching to his
+statements: all the facts of so-called adventitious morphogenesis in
+plants, of regeneration in animals, proved that the morphogenetic
+organisation could not be fully disintegrated during ontogeny. But these
+difficulties were not absolute: they could be overcome: indeed, Weismann
+assumes, that in certain specific cases--and he regarded all cases of
+restoration of a destroyed organisation as due to specific properties
+of the subjects, originated by roundabout variations and natural
+selection--that in specific cases, specific arrangements of minute parts
+were formed during the process of disintegration, and were surrendered
+to specific cells during development, from which regeneration or
+adventitious budding could originate if required. “Plasma of reserve”
+was the name bestowed on these hypothetic arrangements.
+
+Almost independently another German author, Wilhelm Roux,[10] has
+advocated a theoretical view of morphogenesis which very closely
+resembles the hypothesis of Weismann. According to Roux a minute
+ultimate structure is present in the nucleus of the germ and directs
+development by being divided into its parts during the series of nuclear
+divisions.
+
+[10] *Die Bedeutung der Kernteilungsfiguren*, Leipzig, 1883.
+
+But in spite of this similarity of the outset, we enter an altogether
+different field of biological investigation on mentioning Roux’s name:
+we are leaving hypothetic construction, at least in its absoluteness,
+and are entering the realms of scientific experiment in morphology.
+
+
+EXPERIMENTAL MORPHOLOGY
+
+I have told you already in the last lecture that, while in the
+eighteenth century individual morphogenesis had formed the centre of
+biological interest and been studied experimentally in a thoroughly
+adequate manner, that interest gradually diminished, until at last
+the physiology of form as an exact separate science was almost wholly
+forgotten. At least that was the state of affairs as regards zoological
+biology; botanists, it must be granted, have never lost the historical
+continuity to such a degree; botany has never ceased to be regarded
+as one science and never was broken up into parts as zoology was.
+Zoological physiology and zoological morphology indeed were for many
+years in a relationship to one another not very much closer than the
+relation between philology and chemistry.
+
+There were always a few men, of course, who strove against the current.
+The late Wilhelm His,[11] instance, described the embryology of the
+chick in an original manner, in order to find out the mechanical
+relations of embryonic parts, by which passive deformation, as an
+integrating part of morphogenesis, might be induced. He also most
+clearly stated the ultimate aim of embryology to be the mathematical
+derivation of the adult form from the distribution of growth in the
+germ. To Alexander Goette[12] we owe another set of analytical
+considerations about ontogeny. Newport, as early as 1850, and in
+later years Pflüger and Rauber, carried out experiments on the eggs
+of the frog, which may truly be called anticipatory of what was to
+follow. But it was Wilhelm Roux,[13] now professor of anatomy at
+Halle, who entered the field with a thoroughly elaborated programme,
+who knew not only how to state the problem analytically, but also
+how to attack it, fully convinced of the importance of what he did.
+“Entwickelungsmechanik,”--mechanics of development--he called the “new
+branch of anatomical science” of which he tried to lay the foundations.
+
+[11] *Unsere Körperform*, Leipzig, 1875.
+
+[12] *Die Entwickelungsgeschichte der Unke*, Leipzig, 1875.
+
+[13] *Gesammelte Abhandlungen*, Leipzig, 1895. Most important
+theoretical papers:--*Zeitschr. Biolog.* 21, 1885; *Die
+Entwickelungsmechanik der Organismen*, Wien, 1890; *Vorträge und
+Aufsätze über Entwickelungsmechanik*, Heft i., Leipzig, 1905.
+
+I cannot let this occasion pass without emphasising in the most decided
+manner how highly in my opinion Roux’s services to the systematic
+exploration of morphogenesis must be esteemed. I feel the more obliged
+to do so, because later on I shall have to contradict not only many
+of his positive statements but also most of his theoretical views. He
+himself has lately given up much of what he most strongly advocated only
+ten years ago. But Roux’s place in the history of biological science can
+never be altered, let science take what path it will.
+
+It is not the place here to develop the logic of experiment; least of
+all is it necessary in the country of John Stuart Mill. All of you know
+that experiment, by its method of isolating the single constituents
+of complicated phenomena, is the principal aid in the discovery of
+so-called causal relations. Let us try then to see what causal
+relations Wilhelm Roux established with the aid of morphogenetic
+experiment.
+
+
+THE WORK OF WILHELM ROUX
+
+We know already that an hypothesis about the foundation of individual
+development was his starting-point. Like Weismann he supposed that
+there exists a very complicated structure in the germ, and that nuclear
+division leads to the disintegration of that structure. He next tried to
+bring forward what might be called a number of indicia supporting his
+view.
+
+A close relation had been found to exist in many cases between the
+direction of the first cleavage furrows of the germ and the direction
+of the chief planes of symmetry in the adult: the first cleavage, for
+instance, very often corresponds to the median plane, or stands at right
+angles to it. And in other instances, such as have been worked out into
+the doctrine of so-called “cell-lineages,” typical cleavage cells were
+found to correspond to typical organs. Was not that a strong support
+for a theory which regarded cellular division as the principal means
+of differentiation? It is true, the close relations between cleavage
+and symmetry did not exist in every case, but then there had always
+happened some specific experimental disturbances, *e.g.* influences of
+an abnormal direction of gravity on account of a turning over of the
+egg, and it was easy to reconcile such cases with the generally accepted
+theory on the assumption of what was called “anachronism” of cleavage.
+
+But Roux was not satisfied with mere indicia, he wanted a proof, and
+with this intention he carried out an experiment which has become
+very celebrated.[14] With a hot needle he killed one of the first two
+blastomeres of the frog’s egg after the full accomplishment of its first
+cleavage, and then watched the development of the surviving cell. A
+typical half-embryo was seen to emerge--an organism indeed, which was as
+much a half as if a fully formed embryo of a certain stage had been cut
+in two by a razor. It was especially in the anterior part of the embryo
+that its “halfness” could most clearly be demonstrated.
+
+[14] *Virchow’s Archiv.* 114, 1888.
+
+That seemed to be a proof of Weismann’s and Roux’s theory of
+development, a proof of the hypothesis that there is a very complicated
+structure which promotes ontogeny by its disintegration, carried out
+during the cell divisions of embryology by the aid of the process of
+nuclear division, the so-called “karyokinesis.”
+
+To the dispassionate observer it will appear, I suppose, that the
+conclusions drawn by Roux from his experiment go a little beyond their
+legitimate length. Certainly some sort of “evolutio” is proved by
+rearing half the frog from half the egg. But is anything proved, is
+there anything discovered at all about the nucleus? It was only on
+account of the common opinion about the part it played in morphogenesis
+that the nucleus had been taken into consideration.
+
+Things soon became still more ambiguous.
+
+
+THE EXPERIMENTS ON THE EGG OF THE SEA-URCHIN
+
+Roux’s results were published for the first time in 1888; three years
+later I tried to repeat his fundamental experiment on another subject
+and by a somewhat different method. It was known from the cytological
+researches of the brothers Hertwig and Boveri that the eggs of the
+common sea-urchin (*Echinus microtuberculatus*) are able to stand well
+all sorts of rough treatment, and that, in particular, when broken into
+pieces by shaking, their fragments will survive and continue to segment.
+I took advantage of these facts for my purposes. I shook the germs
+rather violently during their two-cell stage, and in several instances I
+succeeded in killing one of the blastomeres, while the other one was not
+damaged, or in separating the two blastomeres from one another.[15]
+
+[15] *Zeitschr. wiss. Zool.* 53, 1891.
+
+Let us now follow the development of the isolated surviving cell. It
+went through cleavage just as it would have done in contact with its
+sister-cell, and there occurred cleavage stages which were just half
+of the normal ones. The stage, for instance, which corresponded to the
+normal sixteen-cell stage, and which, of course, in my subjects was
+built up of eight elements only, showed two micromeres, two macromeres
+and four cells of medium size, exactly as if a normal sixteen-cell stage
+had been cut in two; and the form of the whole was that of a hemisphere.
+So far there was no divergence from Roux’s results.
+
+The development of our Echinus proceeds rather rapidly, the cleavage
+being accomplished in about fifteen hours. I now noticed on the evening
+of the first day of the experiment, when the half-germ was composed of
+about two hundred elements, that the margin of the hemispherical germ
+bent together a little, as if it were about to form a whole sphere
+of smaller size, and, indeed, the next morning a *whole* diminutive
+blastula was swimming about. I was so much convinced that I should get
+Roux’s morphogenetical result in all its features that, even in spite of
+this whole blastula, I now expected that the next morning would reveal
+to me the half-organisation of my subject once more; the intestine, I
+supposed, might come out quite on one side of it, as a half-tube, and
+the mesenchyme ring might be a half one also.
+
+But things turned out as they were bound to do and not as I had
+expected; there was a typically *whole* gastrula on my dish the next
+morning, differing only by its small size from a normal one; and this
+*small but whole* gastrula was followed by a whole and typical small
+pluteus-larva (Fig. 5).
+
+[Illustration: Fig. 5.--Illustration of Experiments on Echinus.
+
+*a*_1 and *b*_1. Normal gastrula and normal pluteus.
+
+*a*_2 and *b*_2. “Half”-gastrula and “half”-pluteus, that *ought* to result
+from one of the first two blastomeres, when isolated, according to the
+theory of “evolutio.”
+
+*a*_3 and *b*_3. The small *but whole* gastrula and pluteus that actually
+*do* result.]
+
+That was just the opposite of Roux’s result: one of the first two
+blastomeres had undergone a half-cleavage as in his case, but then it
+had become a whole organism by a simple process of rearrangement of its
+material, without anything that resembled regeneration, in the sense of
+a completion by budding from a wound.
+
+If one blastomere of the two-cell stage was thus capable of performing
+the morphogenetical process in its totality, it became, of course,
+*impossible* to allow that nuclear division had separated any sort of
+“germ-plasm” into two different halves, and not even the protoplasm of
+the egg could be said to have been divided by the first cleavage furrow
+into unequal parts, as the postulate of the strict theory of so-called
+“evolutio” had been. This was a very important result, sufficient
+alone to overthrow at once the theory of ontogenetical “evolutio,”
+the “Mosaiktheorie” as it had been called--not by Roux himself, but
+according to his views--in its exclusiveness.
+
+After first widening the circle of my observations by showing that
+one of the first four blastomeres is capable of performing a whole
+organogenesis, and that three of the first four blastomeres together
+result in an absolutely perfect organism, I went on to follow up
+separately one of the two fundamental problems which had been suggested
+by my first experiment: was there anything more to find out about
+the importance or unimportance of the single *nuclear* divisions in
+morphogenesis?[16]
+
+[16] *Zeitschr. wiss. Zool.* 55, 1892.
+
+By raising the temperature of the medium or by diluting the sea-water to
+a certain degree it proved at first to be possible to alter in a rather
+fundamental way the type of the cleavage-stages without any damage to
+the resulting organism. There may be no micromeres at the sixteen-cell
+stage, or they may appear as early as in the stage of eight cells;
+no matter, the larva is bound to be typical. So it certainly is not
+necessary for all the cleavages to occur just in their normal order.
+
+But of greater importance for our purposes was what followed. I
+succeeded in pressing the eggs of Echinus between two glass plates,
+rather tightly, but without killing them; the eggs became deformed to
+comparatively flat plates of a large diameter. Now in these eggs all
+nuclear division occurred at right angles to the direction of pressure,
+that is to say, in the direction of the plates, as long as the pressure
+lasted; but the divisions began to occur at right angles to their former
+direction, as soon as the pressure ceased. By letting the pressure be
+at work for different times I therefore, of course, had it quite in my
+power to obtain cleavage types just as I wanted to get them. If, for
+instance, I kept the eggs under pressure until the eight-cell stage was
+complete, I got a plate of eight cells one beside the other, instead of
+two rings, of four cells each, one above the other, as in the normal
+case; but the next cell division occurred at right angles to the former
+ones, and a sixteen-cell stage, of two plates of eight cells each, one
+above the other, was the result. If the pressure continued until the
+sixteen-cell stage was reached, sixteen cells lay together in one plate,
+and two plates of sixteen cells each, one above the other, were the
+result of the next cleavage.
+
+We are not, however, studying these things for cytological, but for
+morphogenetical purposes, and for these the cleavage phenomenon itself
+is less important than the organogenetic result of it: all our subjects
+resulted in *absolutely normal* organisms. Now, it is clear, that the
+spatial relations of the different nuclear divisions to each other are
+anything but normal, in the eggs subjected to the pressure experiments;
+that, so to say, every nucleus has got quite different neighbours if
+compared with the “normal” case. If that makes no difference, then
+there *cannot* exist any close relation between the single nuclear
+divisions and organogenesis at all, and the conclusion we have drawn
+more provisionally from the whole development of isolated blastomeres
+has been extended and proved in the most perfect manner. There ought to
+result a morphogenetic chaos according to the theory of real “evolutio”
+carried out by nuclear division, if the positions of the single nuclei
+were fundamentally changed with regard to one another (Fig. 6). But now
+there resulted not chaos, but the normal organisation: therefore it was
+disproved in the strictest way that nuclear divisions have any bearing
+on the origin of organisation; at least as far as the divisions during
+cleavage come into account.
+
+[Illustration: Fig. 6.--Pressure-experiments on Echinus.
+
+*a*_1 and *b*_1. Two normal cleavage stages, consisting of eight and
+sixteen cells.
+
+*a*_2 and *b*_2. Corresponding stages modified by exerting pressure
+until the eight-cell stage was finished. See text.]
+
+On the egg of the frog (O. Hertwig), and on the egg of annelids (E. B.
+Wilson), my pressure experiments have been carried out with the same
+result.[17]
+
+[17] In the pressure experiments I had altered the relative position of
+the nuclei *in origine*. In later years I succeeded in disturbing the
+arrangement of the fully formed cells of the eight-cell stage, and in
+getting normal larvæ in spite of that in many cases. But as this series
+of experiments is not free from certain complications--which in part
+will be understood later on (see page 73)--it must suffice here to have
+mentioned them. (For further information see my paper in *Archiv. f.
+Entwickelungsmechanik*, xiv., 1902, page 500.)
+
+
+ON THE INTIMATE STRUCTURE OF THE PROTOPLASM OF THE GERM
+
+Nuclear division, as we have seen, cannot be the basis of organogenesis,
+and all we know about the whole development of isolated blastomeres
+seems to show that there exists nothing responsible for differentiation
+in the protoplasm either.
+
+But would that be possible? It cannot appear possible on a more profound
+consideration of the nature of morphogenesis, it seems to me: as the
+untypical agents of the medium cannot be responsible in any way for
+the origin of a form combination which is most typical and specific,
+there must be somewhere in the egg itself a certain factor which is
+responsible at least for the general orientation and symmetry of it.
+Considerations of this kind led me, as early as 1893,[18] to urge the
+hypothesis that there existed, that there *must* exist, a sort of
+intimate structure in the egg, including polarity and bilaterality as
+the chief features of its symmetry, a structure which belongs to every
+smallest element of the egg, and which might be imagined by analogy
+under the form of elementary magnets.[19] This hypothetic structure
+could have its seat in the protoplasm only. In the egg of echinoderms it
+would be capable of such a quick rearrangement after being disturbed,
+that it could not be observed but only inferred logically; there might,
+however, be cases in which its real discovery would be possible. Indeed
+Roux’s frog-experiment seems to be a case where it is found to be at
+work: at least it seems very probable to assume that Roux obtained half
+of a frog’s embryo because the protoplasm of the isolated blastomere had
+preserved the “halfness” of its intimate structure, and had not been
+able to form a small whole out of it.
+
+[18] *Mitteil. Neapel. 11, 1893.*
+
+[19] But the elementary magnets would have to be bilateral!
+
+Of course it was my principal object to verify this hypothesis, and
+such verification became possible in a set of experiments which my
+friend T. H. Morgan and myself carried out together,[20] in 1895, on
+the eggs of ctenophores, a sort of pelagic animals, somewhat resembling
+the jelly-fish, but of a rather different inner organisation. The
+zoologist Chun had found even before Roux’s analytical studies, that
+isolated blastomeres of the ctenophore egg behave like parts of the
+whole and result in a half-organisation like the frog’s germ does. Chun
+had not laid much stress on his discovery, which now, of course, from
+the new points of view, became a very important one. We first repeated
+Chun’s experiment and obtained his results, with the sole exception
+that there was a tendency of the endoderm of the half-larva of Beroë
+to become more than “half.” But that was not what we chiefly wanted to
+study. We succeeded in cutting away a certain mass of the protoplasm
+of the ctenophore egg just before it began to cleave, without damaging
+its nuclear material in any way: in all cases, where the cut was
+performed at the side, there resulted a certain type of larvae from
+our experiments which showed exactly the same sort of defects as were
+present in larvae developed from one of the first two blastomeres alone.
+
+[20] *Arch. Entw. Mech.* 2, 1895.
+
+The hypothesis of the morphogenetic importance of *protoplasm* had thus
+been proved. In our experiments there was all of the nuclear material,
+but there were defects on one side of the protoplasm of the egg; and the
+defects in the adult were found to correspond to these defects in the
+protoplasm.
+
+And now O. Schultze and Morgan succeeded in performing some experiments
+which directly proved the hypothesis of the part played by protoplasm
+in the subject employed by Roux, *viz.*, the frog’s egg. The first of
+these investigators managed to rear two whole frog embryos of small
+size, if he slightly pressed the two-cell stage of that form between
+two plates of glass and turned it over; and Morgan,[21] after having
+killed one of the first two blastomeres, as was done in the original
+experiment of Roux, was able to bring the surviving one to a half or
+to a whole development according as it was undisturbed or turned.
+There cannot be any doubt that in both of these cases, it is the
+possibility of a rearrangement of protoplasm, offered by the turning
+over, which allows the isolated blastomere to develop as a whole. The
+regulation of the frog’s egg, with regard to its becoming whole, may be
+called facultative, whilst the same regulation of the egg of Echinus
+is obligatory. It is not without interest to note that the first two
+blastomeres of the common newt, *i.e.* of a form which belongs to the
+other class of Amphibia, after a separation of *any* kind, *always*
+develop as wholes, their faculty of regulation being obligatory, like
+that of Echinus.
+
+[21] *Anat. Anz.* 10, 1895.
+
+Whole or partial development may thus be dependent on the power of
+regulation contained in the intimate polar-bilateral structure of the
+protoplasm. Where this is so, the regulation and the differences in
+development are both connected with the chief relations of symmetry.
+The development becomes a half or a quarter of the normal because
+there is only one-half or one-quarter of a certain structure present,
+one-half or one-quarter with regard to the very wholeness of this
+structure; the development is whole, in spite of disturbances, if
+the intimate structure became whole first. We may describe the
+“wholeness,” “halfness,” or “quarterness” of our hypothetic structure
+in a mathematical way, by using three axes, at right angles to one
+another, as the base of orientation. To each of these, *x*, *y*, and
+*z*, a certain specific state with regard to the symmetrical relations
+corresponds; thence it follows that, if there are wanting all those
+parts of the intimate structure which are determined, say, by a negative
+value of *y*, by minus *y*, then there is wanting half of the intimate
+structure; and this halfness of the intimate structure is followed by
+the halfness of organogenesis, the dependence of the latter on the
+intimate structure being established. But if regulation has restored,
+on a smaller scale, the whole of the arrangement according to all values
+of *x*, *y* and *z*, development also can take place completely (Fig. 7).
+
+[Illustration: Fig. 7.--Diagram illustrating the intimate Regulation of
+Protoplasm from “Half” to “Whole.”
+
+The large circle represents the original structure of the egg. In all
+cases where cleavage-cells of the two-cell stage are isolated this
+original structure is only present as “half” in the beginning, say
+only on the right (+*y*) side. Development then becomes “half,” if the
+intimate structure remains half; but it becomes “whole” (on a smaller
+scale) if a new whole-structure (small circle!) is formed by regulatory
+processes.]
+
+I am quite aware that such a discussion is rather empty and purely
+formal, nevertheless it is by no means without value, for it shows
+most clearly the differences between what we have called the intimate
+structure of germs, responsible only for the general symmetry of
+themselves and of their isolated parts, and another sort of possible
+structure of the egg-protoplasm which we now shall have to consider, and
+which, at the first glance, seems to form a serious difficulty to our
+statements, as far at least as they claim to be of general importance.
+The study of this other sort of germinal structure at the same time will
+lead us a step farther in our historical sketch of the first years of
+“Entwickelungsmechanik” and will bring this sketch to its end.
+
+
+ON SOME SPECIFICITIES OF ORGANISATION IN CERTAIN GERMS
+
+It was known already about 1890, from the careful study of what has
+been called “cell-lineage,” that in the eggs of several families of
+the animal kingdom the origin of certain organs may be traced back to
+individual cells of cleavage, having a typical histological character
+of their own. In America especially such researches have been carried
+out with the utmost minuteness, E. B. Wilson’s study of the cell-lineage
+of the Annelid *Nereis* being the first of them. If it were true that
+nuclear division is of no determining influence upon the ontogenetic
+fate of the blastomeres, only peculiarities of the different parts of
+the protoplasm could account for such relations of special cleavage
+cells to special organs. I advocated this view as early as in 1894,
+and it was proved two years later by Crampton, a pupil of Wilson’s,
+in some very fine experiments performed on the germ of a certain
+mollusc.[22] The egg of this form contains a special sort of protoplasm
+near its vegetative pole, and this part of it is separated at each
+of the first two segmentations by a sort of pseudo-cleavage, leading
+to stages of three and five separated masses instead of two and four,
+the supernumerary mass being the so-called “yolk-sac” and possessing
+no nuclear elements (Fig. 8). Crampton removed this yolk-sac at the
+two-cell stage, and he found that the cleavage of the germs thus
+operated upon was normal except with regard to the size and histological
+appearance of one cell, and that the larvae originating from these
+germs were complete in every respect except in their mesenchyme, which
+was wanting. A special part of the protoplasm of the egg had thus been
+brought into relation with quite a special part of organisation, *and
+that special part of the protoplasm contained no nucleus*.
+
+[22] *Arch. Entw. Mech.* 3, 1896.
+
+[Illustration: Fig. 8.--The Mollusc Dentalium (*after* E. B. Wilson).
+
+*a.* The egg, consisting of three different kinds of protoplasmatic
+material.
+
+*b.* First cleavage-stage. There are two cells and one “pseudo-cell,”
+the yolk-sac, which contains no nucleus. This was removed in Crampton’s
+experiment.]
+
+
+GENERAL RESULTS OF THE FIRST PERIOD OF “ENTWICKELUNGSMECHANIK”
+
+This experiment of Crampton’s, afterwards confirmed by Wilson himself,
+may be said to have closed the first period of the new science of
+physiology of form, a period devoted almost exclusively to the problem
+whether the theory of nuclear division or, in a wider sense, whether the
+theory of a strict “evolutio” as the basis of organogenesis was true or
+not.
+
+It was shown, as we have seen, that the theory of the “qualitatively
+unequal nuclear division” (“qualitativ-ungleiche Kernteilung” in German)
+certainly was not true, and that there also was no strict “evolutio”
+in protoplasm. Hence Weismann’s theory was clearly disproved. There
+certainly is a good deal of real “epigenesis” in ontogeny, a good deal
+of “production of manifoldness,” not only with regard to visibility but
+in a more profound meaning. But some sort of pre-formation had also
+been proved to exist, and this pre-formation, or, if you like, this
+restricted evolution, was found to be of two different kinds. First an
+intimate organisation of the protoplasm, spoken of as its polarity and
+bilaterality, was discovered, and this had to be postulated for every
+kind of germs, even when it was overshadowed by immediate obligatory
+regulation after disturbances. Besides that there were cases in which
+a real specificity of special parts of the germ existed, a relation of
+these special parts to special organs: but this sort of specification
+also was shown to belong to the protoplasm.
+
+It follows from all we have mentioned about the organisation of
+protoplasm and its bearing on morphogenesis, that the eggs of different
+animals may behave rather differently, in this respect, and that
+the eggs indeed may be classified according to the degree of their
+organisation. Though we must leave a detailed discussion of these
+topics to morphology proper, we yet shall try shortly to summarise
+what has been ascertained about them in the different classes of the
+animal kingdom. A full regulation of the *intimate* structure of
+isolated blastomeres to a new whole, has been proved to exist in the
+highest degree in the eggs of all echinoderms, medusae, nemertines,
+Amphioxus, fishes, and in one class of the Amphibia (the *Urodela*);
+it is facultative only among the other class of Amphibia, the *Anura*,
+and seems to be only partly developed or to be wanting altogether among
+ctenophora, ascidia, annelids, and mollusca. Peculiarities in the
+organisation of *specific parts* of protoplasm have been proved to occur
+in more cases than at first had been assumed; they exist even in the
+echinoderm egg, as experiments of the last few years have shown; even
+here a sort of specification exists at the vegetative pole of the egg,
+though it is liable to a certain kind of regulation; the same is true in
+medusae, nemertines, etc.; but among molluscs, ascidians, and annelids
+no regulation about the specific organisation of the germ in cleavage
+has been found in any case.
+
+The differences in the degree of regulability of the intimate germinal
+structure may easily be reduced to simple differences in the physical
+consistency of their protoplasm.[23] But all differences in specific
+organisation must remain as they are for the present; it will be one of
+the aims of the future theory of development to trace these differences
+also to a common source.
+
+[23] It deserves notice in this connection, that in some cases the
+protoplasm of parts of a germ has been found to be more regulable in
+the earliest stages, when it is very fluid, than later, when it is more
+stiff.
+
+That such an endeavour will probably be not without success, is clear,
+I should think, from the mere fact that differences with regard to
+germinal specific pre-formation do not agree in any way with the
+systematic position of the animals exhibiting them; for, strange as it
+would be if there were two utterly different kinds of morphogenesis, it
+would be still more strange if there were differences in morphogenesis
+which were totally unconnected with systematic relationship: the
+ctenophores behaving differently from the medusae, and Amphioxus
+differently from ascidians.
+
+
+SOME NEW RESULTS CONCERNING RESTITUTIONS
+
+We now might close this chapter, which has chiefly dealt with the
+disproof of a certain sort of ontogenetic theories, and therefore
+has been almost negative in its character, did it not seem desirable
+to add at least a few words about the later discoveries relating to
+morphogenetic restorations of the adult. We have learnt that Weismann
+created his concept of “reserve plasma” to account for what little
+he knew about “restitutions”: that is, about the restoration of lost
+parts: he only knew regeneration proper in animals and the formation of
+adventitious buds in plants. It is common to both of these phenomena
+that they take their origin from typically localised points of the body
+in every case; each time they occur a certain well-defined part of the
+body is charged with the restoration of the lost parts. To explain
+such cases Weismann’s hypothesis was quite adequate, at least in a
+logical sense. But at present, as we shall discuss more fully in another
+chapter, we know of some very widespread forms of restitution, in which
+what is to be done for a replacement of the lost is not entrusted to
+*one* typical part of the body in every case, but in which the whole
+of the morphogenetic action to be performed is transferred in its
+*single* parts to the *single* parts of the body which is accomplishing
+restoration: each of its parts has to take an individual share in the
+process of restoration, effecting what is properly called a certain kind
+of “re-differentiation” (“Umdifferenzierung”), and this share varies
+according to the relative position of the part in each case. Later on
+these statements will appear in more correct form than at present, and
+then it will become clear that we are fully entitled to emphasise at the
+end of our criticism of Weismann’s theory, that his hypothesis relating
+to restorations can be no more true than his theory of development
+proper was found to be.
+
+And now we shall pass on to our positive work.
+
+We shall try to sketch the outlines of what might properly be called an
+*analytical theory of morphogenesis*; that is, to explain the sum of our
+knowledge about organic form-production, gained by experiment and by
+logical analysis, in the form of a real system, in which each part will
+be, or at least will try to be, in its proper place and in relation with
+every other part. Our analytical work will give us ample opportunity of
+mentioning many important topics of so-called general physiology also,
+irrespective of morphogenesis as such. But morphogenesis is always to
+be the centre and starting-point of our analysis. As I myself approach
+the subject as a zoologist, animal morphogenesis, as before, will be the
+principal subject of what is to follow.
+
+
+2. ANALYTICAL THEORY OF MORPHOGENESIS[24]
+
+[24] Compare my *Analytische Theorie der organischen Entwickelung*,
+Leipzig, 1894, and my reviews in *Ergebnisse der Anatomie und
+Entwickelungsgeschichte*, vols. viii. xi. xiv., 1899-1905. A shorter
+review is given in *Ergebnisse der Physiologie*, vol. v., 1906. The full
+literature will be found in these reviews.
+
+α. THE DISTRIBUTION OF MORPHOGENETIC POTENCIES
+
+*Prospective Value and Prospective Potency*
+
+Wilhelm Roux did not fail to see that the questions of the locality and
+the time of all morphogenetic differentiations had to be solved first,
+before any problem of causality proper could be attacked. From this
+point of view he carried out his fundamental experiments.
+
+It is only in terminology that we differ from his views, if we prefer
+to call our introductory chapter an analysis of the distribution of
+morphogenetic potencies. The result will be of course rather different
+from what Roux expected it would be.
+
+Let us begin by laying down two fundamental concepts. Suppose we have
+here a definite embryo in a definite state of development, say a
+blastula, or a gastrula, or some sort of larva, then we are entitled
+to study any special element of any special elementary organ of this
+germ with respect to what is actually to develop out of this very
+element in the future actual course of this development, whether it be
+undisturbed or disturbed in any way; it is, so to say, the actual, *the
+real fate* of our element, that we take in account. I have proposed to
+call this real fate of each embryonic part in this very definite line
+of morphogenesis its *prospective value* (“prospective Bedeutung” in
+German). The fundamental question of the first chapter of our analytical
+theory of development may now be stated as follows: Is the prospective
+value of each part of any state of the morphogenetic line constant,
+*i.e.* is it unchangeable, can it be nothing but one; or is it variable,
+may it change according to different circumstances?
+
+We first introduce a second concept: the term *prospective potency*
+(“prospective Potenz” in German) of each embryonic element. The term
+“prospective morphogenetic potency” is to signify the *possible
+fate* of each of those elements. With the aid of our two artificial
+concepts we are now able to formulate our introductory question thus:
+Is the prospective potency of each embryonic part fully given by
+its prospective value in a certain definite case; is it, so to say,
+identical with it, or does the prospective potency contain more than the
+prospective value of an element in a certain case reveals?
+
+We know already from our historical sketch that the latter is true: that
+the actual fate of a part need not be identical with its possible fate,
+at least in many cases; that the potency of the first four blastomeres
+of the egg of the sea-urchin, for instance, has a far wider range than
+is shown by what each of them actually performs in even this ontogeny.
+There are more morphogenetic possibilities contained in each embryonic
+part than are actually realised in a special morphogenetic case.
+
+As the most important special morphogenetic case is, of course, the
+so-called “normal” one, we can also express our formula in terms of
+special reference to it: there are more morphogenetic possibilities in
+each part than the observation of the normal development can reveal.
+Thus we have at once justified the application of analytical experiment
+to morphogenesis, and have stated its most important results.
+
+As the introductory experiments about “Entwickelungsmechanik” have shown
+already that the prospective potency of embryonic parts, at least in
+certain cases, *can* exceed their prospective value--that, at least in
+certain cases, it can be different from it--the concept of prospective
+potency at the very beginning of our studies puts itself in the centre
+of analytical interest, leaving to the concept of prospective value the
+second place only. For that each embryonic part actually has a certain
+prospective value, a specified actual fate in every single case of
+ontogeny, is clear from itself and does not affirm more than the reality
+of morphogenetic cases in general; but that the prospective value of the
+elements may change, that there is a morphogenetic power in them, which
+contains more than actuality; in other words, that the term “prospective
+potency” has not only a logical but a factual interest: all these points
+amount to a statement not only of the most fundamental introductory
+results but also of the actual *problems* of the physiology of form.
+
+If at each point of the germ something else *can* be formed than
+actually is formed, why then does there happen in each case just what
+happens and nothing else? In these words indeed we may state the chief
+problem of our science, at least after the fundamental relation of
+the superiority of prospective potency to prospective value has been
+generally shown.
+
+We consequently may shortly formulate our first problem as the question
+of the distribution of the prospective morphogenetic potencies in the
+germ. Now this general question involves a number of particular ones.
+Up to what stage, if at all, is there an absolutely equal distribution
+of the potencies over all the elements of the germ? When such an equal
+distribution has ceased to exist at a certain stage, what are then the
+relations between the parts of different potency? How, on the other
+hand, does a newly arisen, more specialised sort of potency behave with
+regard to the original general potency, and what about the distribution
+of the more restricted potency?
+
+I know very well that all such questions will seem to you a little
+formal, and, so to say, academical at the outset. We shall not fail to
+attach to them very concrete meanings.
+
+*The Potencies of the Blastomeres*
+
+At first we turn back to our experiments on the egg of the sea-urchin
+as a type of the germ in the very earliest stages. We know already that
+each of the first two, or each of the first four, or three of the first
+four blastomeres together may produce a whole organism. We may add that
+the swimming blastula, consisting of about one thousand cells, when cut
+in two quite at random, in a plane coincident with, or at least passing
+near, its polar axis, may form two fully developed organisms out of its
+halves.[25] We may formulate this result in the words: the prospective
+potency of the single cells of a blastula of Echinus is the same for
+all of them; their prospective value is as far as possible from being
+constant.
+
+[25] If the plane of section passes near the equator of the germ, two
+whole larvae may be formed also, but in the majority of cases the
+“animal” half does not go beyond the blastula. The specific features of
+the organisation of the protoplasm come into account here. See also page
+65, note 1.
+
+But we may say even a little more: what actually will happen in each of
+the blastula cells in any special case of development experimentally
+determined depends on the position of that cell in the whole, if the
+“whole” is put into relation with any fixed system of co-ordinates; or
+more shortly, “the prospective value of any blastula cell is a function
+of its position in the whole.”
+
+I know from former experience that this statement wants a few words of
+explanation. The word “function” is employed here in the most general,
+mathematical sense, simply to express that the prospective value,
+the actual fate of a cell, will change, whenever its position in the
+whole is different.[26] The “whole” may be related to any three axes
+drawn through the normal undisturbed egg, on the hypothesis that there
+exists a primary polarity and bilaterality of the germ; the axes which
+determine this sort of symmetry may, of course, conveniently be taken as
+co-ordinates; but that is not necessary.
+
+[26] A change of the position of the cell is of course effected by each
+variation of the direction of the cut, which is purely a matter of
+chance.
+
+*The Potencies of Elementary Organs in General*
+
+Before dealing with other very young germs, I think it advisable to
+describe first an experiment which is carried out at a later stage of
+our well-known form. This experiment will easily lead to a few new
+concepts, which we shall want later on, and will serve, on the other
+hand, as a basis of explanation for some results, obtained from the
+youngest germs of some other animal species, which otherwise would seem
+to be rather irreconcilable with what our Echinus teaches us.
+
+You know, from the second lecture, what a gastrula of our sea-urchin
+is. If you bisect this gastrula, when it is completely formed, or
+still better, if you bisect the gastrula of the starfish, either along
+the axis or at right angles to it, you get complete little organisms
+developed from the parts: the ectoderm is formed in the typical manner
+in the parts, and so is the endoderm; everything is proportionate and
+only smaller than in the normal case. So we have at once the important
+results, that, as in the blastula, so in the ectoderm and in the
+endoderm of our Echinus or of the starfish, the prospective potencies
+are the same for every single element: both in the ectoderm and in
+the endoderm the prospective value of each cell is a “function of its
+position” (Fig. 9).
+
+[Illustration: Fig. 9.--The Starfish, *Asterias*.
+
+*a*^1. Normal gastrula; may be bisected along the main axis or at right
+angles to it (see dotted lines).
+
+*a*^2. Normal larva, “*Bipinnaria*.”
+
+*b*^1. Small but whole gastrula that results by a process of regulation
+from the parts of a bisected gastrula.
+
+*b*^2. Small *but whole* “*Bipinnaria*,” developed out of *b*^1.]
+
+But a further experiment has been made on our gastrula. If at the moment
+when the material of the future intestine is most distinctly marked in
+the blastoderm, but not yet grown into a tube, if at this moment the
+upper half of the larva is separated from the lower by an equatorial
+section, you will get a complete larva only from that part which bears
+the “Anlage” of the endoderm, while the other half will proceed in
+morphogenesis very well but will form only ectodermal organs. By another
+sort of experiment, which we cannot fully explain here, it has been
+shown that the endoderm if isolated is also only able to form such
+organs as are normally derived from it.
+
+And so we may summarise both our last results by saying: though
+ectoderm and endoderm have their potencies equally distributed amongst
+their respective cells, they possess different potencies compared one
+with the other. And the same relation is found to hold for all cases of
+what we call elementary organs: they are “equipotential,” as we may say,
+in themselves, but of different potencies compared with each other.
+
+*Explicit and Implicit Potencies: Primary and Secondary Potencies*
+
+We shall first give to our concept of “prospective potency” a few words
+of further analytical explanation with the help of our newly obtained
+knowledge.
+
+It is clear from what we have stated that the prospective potencies of
+the ectoderm and of the endoderm, and we may add, of every elementary
+organ in relation to every other, differ between themselves and also in
+comparison with the blastoderm, from which they have originated. But the
+diversity of the endoderm with respect to the ectoderm is not of the
+same kind as its diversity in respect to the blastoderm. The potency
+of the endoderm and that of the ectoderm are both specialised in their
+typical manner, but compared with the potency of the blastoderm they
+may be said not only to be specialised but also to be *restricted*: the
+potency of the blastoderm embraces the whole, that of the so-called
+germ-layer embraces only part of the whole; and this species of
+restriction becomes clearer and clearer the further ontogeny advances:
+at the end of it in the “ultimate elementary organs” there is no
+prospective potency whatever.
+
+A few new terms will serve to state a little more accurately what
+happens. Of course, with regard to all morphogenesis which goes on
+*immediately* from the blastoderm, the potency of the blastoderm is
+restricted as much as are the potencies of the germ layers. We shall
+call this sort of immediate potency *explicit*, and then we see at
+once that, with regard to their explicit potencies, there are only
+differences among the prospective potencies of the elementary organs;
+but with respect to the *implicit* potency of any of these organs, that
+is with respect to their potency as embracing the faculties of all their
+derivations, there are also not only differences but true morphogenetic
+restrictions lying at the very foundations of all embryology.
+
+But now those of you who are familiar with morphogenetic facts will
+object to me, that what we have stated about all sorts of restrictions
+in ontogeny is not true, and you will censure me for having overlooked
+regeneration, adventitious budding, and so on. To some extent the
+criticism would be right, but I am not going to recant; I shall only
+introduce another new concept. We are dealing only with *primary*
+potencies in our present considerations, *i.e.* with potencies which
+lie at the root of true embryology, not with those serving to regulate
+disturbances of the organisation. It is true, we have in some way
+disturbed the development of our sea-urchin’s egg in order to study
+it; more than that, it would have been impossible to study it at all
+without some sort of disturbance, without some sort of operation.
+But, nevertheless, no potencies of what may properly be called the
+*secondary* or restitutive type have been aroused by our operations;
+nothing happened except on the usual lines of organogenesis. It is
+true, some sort of regulation occurred, but that is included among the
+factors of ontogeny proper.
+
+We shall afterwards study more fully and from a more general point of
+view this very important feature of “primary regulation” in its contrast
+to “secondary regulation” phenomena. At present it must be enough to
+say that in speaking of the restriction of the implicit potencies in
+form-building we refer only to potencies of the primary type, which
+contain within themselves some properties of a (primary) regulative
+character.
+
+*The Morphogenetic Function of Maturation in the Light of Recent
+Discoveries*
+
+Turning again to more concrete matters, we shall first try, with the
+knowledge acquired of the potencies of the blastoderm and the so-called
+germ layers of Echinus, to understand certain rather complicated
+results which the experimental morphogenetic study of other animal
+forms has taught us. We know from our historical sketch that there are
+some very important aberrations from the type, to which the Echinus
+germ belongs,[27] *i.e.* the type with an equal distribution of the
+potencies over all the blastomeres. We know not only that in cases where
+a regulation of the intimate structure of the protoplasm fails to occur
+a partial development of isolated cells will take place, but that there
+may even be a typical disposition of typical cells for the formation of
+typical organs only, without any regulability.
+
+[27] The reader will remember (see page 65, note 1), that even the germ
+of Echinus is not quite equipotential along its main axis, but it is
+equipotential in the strictest sense around this axis. The germs of
+certain medusae seem to be equipotential in every respect, even in their
+cleavage stages.
+
+Let us first consider the last case, of which the egg of mollusca is a
+good type: here there is no equal distribution of potencies whatever,
+the cleavage-cells of this germ are a sort of real “mosaic” with regard
+to their morphogenetic potentialities. Is this difference between the
+germ of the echinoderms and the molluscs to remain where it is, and
+not to be elucidated any further? Then there would be rather important
+differences among the germs of different animals, at least with regard
+to the degree of the specification of their cleavage cells, or if we
+ascribe differences among the blastomeres to the organisation of the
+fertilised egg ready for cleavage, there would be differences in the
+morphogenetic organisation of the egg-protoplasm: some eggs would be
+more typically specialised at the very beginning of morphogenesis than
+others.
+
+In the first years of the study of “Entwickelungsmechanik” I pointed out
+that it must never be forgotten that the egg itself is the result of
+organogenesis. If, therefore, there are real mosaic-like specifications
+in some eggs at the beginning of cleavage, or during it, there may
+perhaps have been an *earlier* stage in the individual history of
+the egg which did not show such specifications of the morphogenetic
+structure. Two American authors share the merit of having proved
+this hypothesis. Conklin showed, several years ago, that certain
+intracellular migrations and rearrangements of material do happen in
+the first stages of ovogenesis in certain cases, but it is to E. B.
+Wilson[28] that science owes a proper and definitive elucidation of the
+whole subject. Wilson’s researches, pursued not only by descriptive
+methods,[29] but also by means of analytical experiment, led him to the
+highly important discovery that the eggs of several forms (nemertines,
+molluscs), which after maturation show the mosaic type of specification
+in their protoplasm to a more or less high degree, fail to show any
+kind of specification in the distribution of their potencies before
+maturation has occurred. In the mollusc egg a certain degree of
+specification is shown already before maturation, but nothing to be
+compared with what happens afterwards; in the egg of nemertines there is
+no specification at all in the unripe egg.
+
+[28] *Journ. Exp. Zool.* 1, 1904.
+
+[29] Great caution must be taken in attributing any specific
+morphogenetic part to differently coloured or constructed materials,
+which may be observed in the egg-protoplasm in certain cases. They may
+play such a part, but in other cases they certainly do not (see Lyon,
+*Arch. Entw. Mech.* 23, 1907). The final decision always depends on
+experiment.
+
+Maturation thus becomes a part of ontogeny itself; it is not with
+fertilisation that morphogenesis begins, there is a sort of ontogeny
+anterior to fertilisation.
+
+These words constitute a summary of Wilson’s researches. Taken together
+with the general results obtained about the potencies of the blastula
+and the gastrula of Echinus, they reduce what appeared to be differences
+of degree or even of kind in the specification of the egg-protoplasm *to
+mere differences in the time of the beginning of real morphogenesis*.
+What occurs in some eggs, as in those of Echinus, at the time of the
+definite formation of the germ layers, leading to a specification and
+restriction of their prospective potencies, may happen very much earlier
+in other eggs. But there exists in *every* sort of egg an *earliest*
+stage, in which all parts of its protoplasm are equal as to their
+prospectivity, and in which there are no potential diversities or
+restrictions of any kind.
+
+So much for differences in the *real material* organisation of the germ
+and their bearing on inequipotentialities of the cleavage cells.
+
+*The Intimate Structure of Protoplasm: Further Remarks*
+
+Where a typical half- or quarter-development from isolated blastomeres
+happens to occur, we know already that the impossibility of a regulation
+of the *intimate polar-bilateral* structure may account for it. As this
+impossibility of regulation probably rests on rather simple physical
+conditions[30] it may properly be stated that equal distribution of
+potencies is not wanting but is only overshadowed here. In this respect
+there exists a logical difference of fundamental importance between
+those cases of so-called “partial” or better, “fragmental” development
+of isolated blastomeres in which a certain embryonic organ is wanting
+on account of its specific morphogenetic material being absent, and
+those cases in which the “fragmental” embryo lacks complete “halves” or
+“quarters” with regard to general symmetry on account of the symmetry
+of its intimate structure being irregularly disturbed. This logical
+difference has not always received the attention which it undoubtedly
+deserves. Our hypothetical intimate structure in itself is, of course,
+also a result of factors concerned in ovogenesis. Only in one case do
+we actually know anything about its origin: Roux has shown that in the
+frog it is the accidental path of the fertilising spermatozoon in the
+egg which, together with the polar axis, normally determines the plane
+of bilateral symmetry; but this symmetry may be overcome and replaced
+by another, if gravity is forced to act in an abnormal manner upon the
+protoplasm; the latter showing parts of different specific gravity in
+the eggs of all Amphibia.
+
+[30] It seems that these physical conditions also--besides the real
+specifications in the organisation of the egg--may be different before
+and after maturation or (in other cases) fertilisation. (See Driesch,
+*Archiv f. Entwickelungsmechanik*, 7, p. 98; and Brachet, *ibid.* 22, p.
+325.)
+
+*The Neutrality of the Concept of “Potency”*
+
+Now we may close our rather long chapter on the distribution of
+potencies in the germ; it has been made long, because it will prove to
+be very important for further analytical discussion; and its importance,
+in great measure, is due to its freedom from prepossessions. Indeed,
+the concept of prospective potency does not prejudice anything; we
+have said, it is true, that limitations of potencies may be due to
+the presence of specific parts of organisation in some cases; that,
+at least, they may be connected therewith; but we have not determined
+at all what a prospective potency really is, what the term really is
+to signify. It may seem that such a state of things gives an air of
+emptiness to our discussions, that it leaves uncertain what is the most
+important. But, I think, our way of argument, which tries to reach the
+problems of greatest importance by degrees, though it may be slow, could
+hardly be called wrong and misleading.
+
+
+β. THE “MEANS” OF MORPHOGENESIS
+
+We now proceed to an analysis of what may properly be called the *means*
+of morphogenesis, the word “means” being preferable to the more usual
+one “conditions” in this connection, as the latter would not cover the
+whole field. It is in quite an unpretentious and merely descriptive
+sense that the expression “means” should be understood at present; what
+is usually called “conditions” is part of the morphogenetic means in our
+sense.
+
+β′. *The Internal Elementary Means of Morphogenesis*
+
+We know that all morphogenesis, typical or atypical, primary or
+secondary, goes on by one morphogenetic elementary process following the
+other. Now the very foundation of these elementary processes themselves
+lies in the elementary functions of the organism as far as they result
+in the formation of stable visible products. Therefore the elementary
+functions of the organism may properly be called the internal “means” of
+morphogenesis.
+
+Secretion and migration are among such functions; the former happening
+by the aid of chemical change or by physical separation, the latter by
+the aid of changes in surface tension. But hardly anything more concrete
+has been made out about these or similar points at present.
+
+We therefore make no claim to offer a complete system of the internal
+elementary means of morphogenesis. We shall only select from the whole
+a few topics of remarkable morphogenetic interest, and say a few words
+about each.
+
+But, first of all, let us observe that the elementary means of
+morphogenesis are far from being morphogenesis themselves. The word
+“means” itself implies as much. It would be possible to understand each
+of these single acts in morphogenesis as well as anything, and yet to be
+as far from understanding the whole as ever. All means of morphogenesis
+are only to be considered as the most general frame of events within
+which morphogenesis occurs.
+
+*Some Remarks on the Importance of Surface Tension in
+Morphogenesis.*--There are a few purely physical phenomena which have
+a special importance in organic morphology, all of them connected
+with capillarity or surface tension. Soap-lather is a very familiar
+thing to all of you: you know that the soap-solution is arranged here
+in very thin planes separated by spaces containing air: it was first
+proved by Berthold[31] that the arrangement of cells in organic tissues
+follows the same type as does the arrangement of the single bubbles of
+a soap-lather, and Bütschli[32] added to this the discovery that the
+minute structure of the protoplasm itself is that of a foam also. Of
+course it is not one fluid and one gas which make up the constituents
+of the structure in the organisms, as is the case in the well-known
+inorganic foams, but two fluids, which do not mix with one another. One
+general law holds for all arrangements of this kind: the so-called law
+of least surfaces, expressed by the words that the sum of all surfaces
+existing is a minimum; and it again is a consequence of this law, if
+discussed mathematically, that four lines will always meet in one point
+and three planes in one line. This feature, together with a certain law
+about the relation of the angles meeting in one line to the size of the
+bubbles, is realised most clearly in many structures of organic tissues,
+and makes it highly probable, at least in some cases, that capillarity
+is at work here. In other cases, as for instance in many plants, a kind
+of outside pressure, the so-called tissue tension, may account for the
+arrangement in surfaces *minimae areae*. Cleavage stages are perhaps
+the very best type in which our physical law is expressed: and here
+it may be said to have quite a simple application whenever all of the
+blastomeres are of the same physical kind, whilst some complications
+appear in germs with a specialised organisation and, therefore,
+with differences in the protoplasm of their single blastomeres. In
+such instances we may say that the physical law holds as far as the
+conditions of the system permit, these conditions ordinarily consisting
+in a sort of non-homogeneity of the surfaces.
+
+[31] *Studien über Protoplasmamechanik*, Leipzig, 1886.
+
+[32] *Unters. üb. mikroskopische Schäume und das Protoplasma*, Leipzig,
+1892.
+
+It seems, from the researches of Dreyer,[33] that the formation of
+organic skeletons may also be governed by the physically conditioned
+arrangement of protoplasmatic or cellular elements, and some phenomena
+of migration and rearrangement among cleavage cells, as described by
+Roux, probably also belong here.
+
+[33] *Jena. Zeitschr.* 26, 1892.
+
+But let us never forget that the laws of surface tension only give
+us the most general type of an arrangement of elements in all these
+cases, nothing else. A physical law never accounts for the Specific!
+Capillarity gives us not the least clue to it. As the organic substance,
+at least in many cases, is a fluid, it must of course follow the general
+laws of hydrostatics and hydrodynamics, but life itself is as little
+touched by its fluid-like or foam-like properties as it is by the fact
+that living bodies have a certain weight and mass.
+
+All indeed that has been described may be said to belong, in the
+broadest meaning of the word, to what is called by Roux “correlation of
+masses,” though this author originally intended to express by this term
+only some sorts of passive pressure and deformation amongst embryonic
+parts as discovered especially by His.
+
+We must be cautious in admitting that any organic feature has been
+explained, even in the most general way, by the action of physical
+forces. What at first seems to be the result of mechanical pressure may
+afterwards be found to be an active process of growth, and what at first
+seems to be a full effect of capillarity among homogeneous elements may
+afterwards be shown to depend on specialised metabolic conditions of the
+surfaces as its principal cause.[34]
+
+[34] According to Zur Strassen’s results the early embryology of
+*Ascaris* proceeds almost exclusively by cellular surface-changes: the
+most typical morphogenetic processes are carried out by the aid of this
+“means.” As a whole, the embryology of *Ascaris* stands quite apart and
+presents a great number of unsolved problems; unfortunately, the germ of
+this form has not been accessible to experiment hitherto.
+
+There are other physical phenomena too, which assist morphogenesis;
+osmotic pressure for instance, which is also well known to operate in
+many purely physiological processes. But all these processes are only
+means of the organism, and can never do more than furnish the general
+type of events. They do not constitute life; they are *used* by life;
+let it remain an open question, for the present, how the phenomenon of
+“life” is to be regarded in general.[35]
+
+[35] Rhumbler has recently published a general survey of all attempts to
+“explain” life, and morphogenesis in particular, in a physico-chemical
+way (“Aus dem Lückengebiet zwischen organismischer und anorganismischer
+Natur,” *Ergeb. Anat. u. Entw.-gesch.* 15, 1906). This *very
+pessimistic* survey is the more valuable as it is written by a convinced
+“mechanist.”
+
+*On Growth*.--Among the internal morphogenetical means which are of
+a so-called physiological character, that is, which nobody claims to
+understand physically at present, there is in the first place *growth*,
+which must be regarded as a very essential one.
+
+Analytically we must carefully discriminate between the increase in the
+size of the cavities of an organism by a passive extension of their
+surfaces and the proper growth of the individual cells, which again
+may be due either to mere extension or to real assimilation. Osmotic
+pressure, of course, plays an important part both in the growth of the
+body-cavities and in simple cellular extension. We repeat the caution
+against believing too much to be explained by this phenomenon: it is the
+organism which by the secretion of osmotic substances in the cavities or
+the protoplasm of the cells prepares the ground for growth even of this
+osmotic sort. The real cellular growth which proceeds on the basis of
+assimilation cannot, of course, be accounted for by osmotic events, not
+even in its most general type.
+
+Ontogenetical growth generally sets in, both in animals and in plants,
+after the chief lines of organisation are laid out; it is only the
+formation of the definite histological structures which usually runs
+parallel to it.
+
+*On Cell-division.*--We have already said a good deal about the
+importance of cell-division in ontogeny: it accompanies very many of the
+processes of organisation in all living beings. But even then, there are
+the Protozoa, in the morphogenesis of which it does not occur at all,
+and there have also become known many cases of morphogenesis in higher
+animals, mostly of the type of regulation, in which cellular division
+is almost or wholly wanting. Therefore, cellular division cannot be
+the true reason of differentiation, but is only a process, which
+though necessary in some cases, cannot be essential to it. It must be
+conceded, I believe, that the same conclusion can be drawn from all our
+experiments on very young stages of the germ.
+
+The investigations of the last few years have made it quite clear that
+even in organisms with a high power of morphogenetic regulation it is
+always the form of the whole, but not the individual cell, which is
+subjected to the regulation processes. Starting from certain results
+obtained by T. H. Morgan, I was able to show that in all the small but
+whole larvae, reared from isolated blastomeres, the size of the cells
+remains normal, only their number being reduced; and Boveri has shown
+most clearly that it is always the size of the nucleus--more correctly,
+the mass of the chromatin--which determines how large a cell of a
+certain histological kind is to be. In this view, the cell appears even
+more as a sort of material used by the organism as supplied, just as
+workmen can build the most different buildings with stones of a given
+size.
+
+
+β″. *The External Means of Morphogenesis*
+
+We now know what internal means of morphogenesis are, and so we may
+glance at some of the most important “outer means” or “conditions” of
+organisation.
+
+Like the adult, the germ also requires a certain amount of heat, oxygen,
+and, when it grows up in the sea, salinity in the medium. For the germ,
+as for the adult, there exists not only a minimum but also a maximum
+limit of all the necessary factors of the medium; the same factor which
+at a certain intensity promotes development, disturbs it from a certain
+other intensity upwards.
+
+Within the limits of this minimum and this maximum of every outside
+agent there generally is an increase in the rate of development
+corresponding to the increase of intensity of the agent. The
+acceleration of development by heat has been shown to follow the law of
+the acceleration of chemical processes by a rise of temperature; that
+seems to prove that certain chemical processes go on during the course
+of morphogenesis.
+
+Almost all that has been investigated of the part played by the external
+conditions of development has little bearing on specific morphogenesis
+proper, and therefore may be left out of account here: we must, however,
+lay great stress on the general fact that there *is* a very close
+dependence of morphogenesis on the outside factors, lest we should be
+accused afterwards of having overlooked it.
+
+Of course all “external” means or conditions of morphogenesis can
+actually relate to morphogenetic processes only by becoming in some way
+“internal,” but we unfortunately have no knowledge whatever how this
+happens. We at present are only able to ascertain what must necessarily
+be accomplished in the medium, in order that normal morphogenesis may go
+on, and we can only suppose that there exist certain specific internal
+general states, indispensable for organogenesis but inaccessible to
+present modes of investigation.[36]
+
+[36] Compare the analytical discussions of Klebs, to whom we owe a great
+series of important discoveries in the field of morphogenetic “means”
+in botany. (*Willkürliche Entwickelungsänderungen bei Pflanzen*, Jena,
+1903; see also *Biol. Centralblatt*, vol. xxiv., 1904, and my reply to
+Klebs, *ibid.* 23, 1903.)
+
+*The Discoveries of Herbst.*--There are but few points in the doctrine
+of the external means or conditions of organogenesis which have a
+more special bearing on the specification of proper form, and which
+therefore require to be described here a little more fully. All
+these researches, which have been carried out almost exclusively by
+Herbst,[37] relate to the effect of the chemical components of sea-water
+upon the development of the sea-urchin. If we select the most important
+of Herbst’s results, we must in the first place say a few words on
+the part taken by lime or calcium, not only in establishing specific
+features of form, but in rendering individual morphogenesis possible at
+all. Herbst has found that in sea-water which is deprived of calcium the
+cleavage cells and many tissue cells also completely lose contact with
+each other: cleavage goes on quite well, but after each single division
+the elements are separated; at the end of the process you find the 808
+cells of the germ together at the bottom of the dish, all swimming about
+like infusoria. There seems to be some influence of the calcium salts
+upon the physical state of the surfaces of the blastomeres.
+
+[37] *Arch. Entw. Mech.* 17, 1904.
+
+It is not without interest to note that this discovery has an important
+bearing on the technical side of all experiments dealing with the
+isolation of blastomeres. Since the separation of the single cleavage
+elements ceases as soon as the germs are brought back from the mixture
+without lime into normal sea-water, it of course is possible to separate
+them up to any stage which it is desired to study, and to keep them
+together afterwards. Thus, if for instance you want to study the
+development of isolated cells of the eight-cell stage, you will leave
+the egg in the artificial mixture containing no calcium until the
+third cleavage, which leads from the four- to the eight-cell stage, is
+finished. The single eight cells brought back to normal sea-water at
+this point will give you the eight embryos you want. All researches
+upon the development of isolated blastomeres since the time of Herbst’s
+discovery have been carried out by this method, and it would have been
+quite impossible by the old method of shaking to pursue the study into
+such minute detail as actually has been done. It may be added that
+calcium, besides its cell-uniting action, is also of primary importance
+in the formation of the skeleton.
+
+Among all the other very numerous studies of Herbst we need only mention
+that potassium is necessary for the typical growth of the intestine,
+just as this element has been found necessary for normal growth in
+plants, and that there must be the ion SO_4, or in other terms,
+sulphur salts present in the water, in order that the germs may acquire
+their pigments and their bilateral symmetry. This is indeed a very
+important result, though it cannot be said to be properly understood. It
+is a fact that in water without sulphates the larvae of Echinus retain
+the radial symmetry they have had in the very earliest stages, and may
+even preserve that symmetry on being brought back to normal sea-water if
+they have spent about twenty-four hours in the artificial mixture.
+
+We may now leave the subject of Herbst’s attempts to discover the
+morphogenetic function of the single constituents of normal sea-water,
+and may devote a few words to the other branch of his investigations,
+those dealing with the morphogenetic effects of substances which are not
+present in the water of the sea, but have been added to it artificially.
+Here, among many other achievements, Herbst has made the most
+important discovery that all salts of lithium effect radical changes
+in development.[38] I cannot describe fully here how the so-called
+“lithium larva” originates; let me only mention that its endoderm is
+formed outside instead of inside, that it is far too large, that there
+is a spherical mass between the ectodermal and the endodermal part of
+the germ, that a radial symmetry is established in place of the normal
+bilateralism, that no skeleton exists, and that the mesenchyme cells
+are placed in a quite abnormal position. All these features, though
+abnormal, are typical of the development in lithium. The larvae present
+no really pathological appearance at all, and, therefore, it may indeed
+be said that lithium salts are able to change fundamentally the whole
+course of morphogenesis. It detracts nothing from the importance of
+these discoveries that, at present, they stand quite isolated: only with
+lithium salts has Herbst obtained such strange results, and only upon
+the eggs of echinids, not even upon those of asterids, do lithium salts
+act in this way.
+
+[38] *Zeitschr. wiss. Zool.* 55, 1902; and *Mitt. Neapel.* 11, 1903.
+
+
+γ. THE FORMATIVE CAUSES OR STIMULI
+
+*The Definition of Cause*
+
+We cannot begin the study of the “causes” of the differentiation of
+form without a few words of explanation about the terminology which we
+shall apply. Causality is the most disputed of all categories; many
+modern scientists, particularly in physics, try to avoid the concept of
+cause altogether, and to replace it by mere functional dependence in
+the mathematical meaning of the term. They claim to express completely
+by an equation all that is discoverable about any sort of phenomena
+constantly connected.
+
+I cannot convince myself that such a very restricted view is the right
+one: it is very cautious, no doubt, but it is incomplete, for we *have*
+the concept of the acting “cause” in our Ego and are *forced* to search
+for applications of it in Nature. On the other hand, it does not at all
+escape me that there are many difficulties, or rather ambiguities, in
+applying it.
+
+We may call the “cause” of any event, the sum total of all the
+constellations of facts which must be completed in order that the event
+may occur; it is in this meaning, for instance, that the first principle
+of energetics applies the term in the words *causa aequat effectum*.
+But, by using the word only in this very general sense, we deprive
+ourselves of many conveniences in the further and more particular study
+of Nature. Would it be better to say that the “cause” of any event is
+the very last change which, after all the constellations necessary for
+its start are accomplished, must still take place in order that the
+event may actually occur? Let us see what would follow from such a use
+of the word causality. We here have an animal germ in a certain stage,
+say a larva of Echinus, which is just about to form the intestine; all
+the internal conditions are fulfilled, and there is also a certain
+temperature, a certain salinity, and so on, but there is no oxygen in
+the water: the intestine; of course, will not grow in such a state of
+things, but it soon will when oxygen is allowed to enter the dish.
+Is, therefore, oxygen the cause of the formation of the intestine of
+echinus? Nobody, I think, would care to say so. By such reasoning,
+indeed, the temperature, or sodium, might be called the “cause” of
+any special process of morphogenesis. It, therefore, seems to be of
+little use to give the name of cause to that factor of any necessary
+constellation of events which accidentally happens to be the last that
+is realised. But what is to be done then?
+
+Might we not say that the cause of any morphogenetic process is that
+typical property, or quality, or change, on which its specific character
+depends, on which depends for example, the fact that now it is the
+intestine which appears, while at another time it is the lens of the
+eye? We might very well, but we already have our term for this sort
+of cause, which is nothing else than our prospective potency applied
+to that elementary organ from which the new process takes its origin.
+The prospective potency indeed is the truly immanent cause of every
+specification affecting single organogenetic processes. But we want
+something more than this.
+
+We may find what we want by considering that each single elementary
+process or development not only has its specification, but also has
+its specific and typical place in the whole--its locality. Therefore
+we shall call the “cause” of a single morphogenetic process, that
+occurrence on which depends its *localisation*, whether its specific
+character also partly depends on this “cause” or not.[39]
+
+[39] In certain cases part of the specific feature of the process in
+question may also depend on the “cause” which is localising it, *e.g.*
+in the galls of plants.
+
+This definition of “cause” in morphology may be artificial; in any
+case it is clear. And at the same time the concepts of the prospective
+potency and of the “means” of organogenesis now acquire a clear and
+definite meaning: potency is the real basis of the specific character
+of every act in morphogenesis, and “means,” including conditions, are
+the sum of all external and internal general circumstances which must be
+present in order that morphogenetic processes may go on, without being
+responsible for their specificity or localisation.
+
+It is implied in these definitions of cause and potency, that the former
+almost always will be of that general type which usually is called a
+stimulus or “Auslösung,” to use the untranslatable German word. There is
+no quantitative correspondence between our “cause” and the morphogenetic
+effect.
+
+*Some Instances of Formative and Directive Stimuli*
+
+Again it is to Herbst that we owe not only a very thorough logical
+analysis of what he calls “formative and directive stimuli”[40] but also
+some important discoveries on this subject. We cannot do more here than
+barely mention some of the most characteristic facts.
+
+[40] Herbst, “Ueber die Bedeutung die Reizphysiologie für die kausale
+Auffassung von Vorgängen in der tierischen Ontogenese” (*Biol.
+Centralblatt*, vols. xiv., 1894, and xv., 1895); *Formative Reize in der
+tierischen Ontogenese*, Leipzig, 1901. These important papers must be
+studied by every one who wishes to become familiar with the subject. The
+present state of science is reviewed in my articles in the *Ergebnisse
+der Anatomie und Entwickelungsgeschichte*, vols. xi. and xiv., 1902 and
+1905.
+
+Amongst plants it has long been known that the direction of light or of
+gravity may determine where roots or branches or other morphogenetic
+formations are to arise; in hydroids also we know that these factors
+of the medium may be at work[41] as morphogenetic causes, though most
+of the typical architecture of hydroid colonies certainly is due to
+internal causes, as is also much of the organisation in plants.
+
+[41] Compare the important papers by J. Loeb, *Untersuchungen zur
+physiologischen Morphologie der Tiere*, Würzburg, 1891-2.
+
+Light and gravity are external formative causes; beside that they are
+merely “localisers.” But there also are some external formative stimuli,
+on which depends not only the place of the effect, but also part of its
+specification. The galls of plants are the most typical organogenetic
+results of such stimuli. The potencies of the plant and the specific
+kind of the stimulus equally contribute to their specification; for
+several kinds of galls may originate on one sort of leaves.
+
+Scarcely any exterior formative stimuli are responsible for animal
+organisation; and one would hardly be wrong in saying that this
+morphogenetic independence in animals is due to their comparatively
+far-reaching functional independence of those external agents which
+have any sort of direction. But many organogenetic relations are known
+to exist between the single parts of animal germs, each of these parts
+being in some respect external to every other; and, indeed, it might
+have been expected already *a priori*, that such formative relations
+between the parts of an animal embryo must exist, after all we have
+learned about the chief lines of early embryology. If differentiation
+does not go on after the scheme of Weismann, that is, if it is not
+carried out by true “evolutio” from within, how could it be effected
+except from without? Indeed, every embryonic part may in some respect be
+a possible cause for morphogenetic events, which are to occur on every
+other part: it is here that the very roots of epigenesis are to be found.
+
+Heliotropism and geotropism are among the well-known physiological
+functions of plants: the roots are seen to bend away from the light and
+towards the ground; the branches behave just in the opposite way. It now
+has been supposed by Herbst that such “directive stimuli” may also be
+at work among the growing or wandering parts of the embryo, that their
+growth or their migration may be determined by the typical character of
+other parts, and that real morphogenetic characters can be the result of
+some such relation; a sort of “chemotropism” or “chemotaxis” may be at
+work here. Herbst himself has discussed theoretically several cases of
+organogenesis in which the action of directive stimuli is very probable.
+What has become actually known by experiment is not very much at
+present: the mesenchyme cells of Echinus are directed in their migration
+by specified places in the ectoderm, the pigment cells of the yolk-sac
+of the fish fundulus are attracted by its blood vessels, and nerves
+may be forced to turn into little tubes containing brain substance;
+but of course only the first two instances have any bearing on typical
+morphogenesis.
+
+The first case of an “internal formative stimulus” in the proper sense,
+that is, of one embryonic part causing another to appear, was discovered
+by Herbst himself. The arms of the so-called pluteus of the sea-urchin
+are in formative dependence on the skeleton--no skeleton, no arms; so
+many skeleton primordia,[42] in abnormal cases, so many arms; abnormal
+position of the skeleton, abnormal position of the arms: these three
+experimental observations form the proof of this morphogenetic relation.
+
+[42] I use the word “primordia” for the German “Anlage”; it is better
+than the word “rudiment,” as the latter may also serve to signify
+the very last stage of a certain formation that is disappearing
+(phylogenetically).
+
+It may be simple mechanical contact, or it may be some chemical
+influence that really constitutes the “stimulus” in this case;
+certainly, there exists a close and very specific relation of the
+localisation of one part of the embryo to another. Things are much the
+same in another case, which, after having been hypothetically stated
+by Herbst on the basis of pathological data, was proved experimentally
+by Spemann. The lens of the eye of certain Amphibia is formed of their
+skin in response to a formative stimulus proceeding from the so-called
+primary optic vesicle. If this vesicle fails to touch the skin, no lens
+appears; and, on the other hand, the lens may appear in quite abnormal
+parts of the skin if they come into contact with the optic vesicle after
+transplantation.
+
+But formative dependence of parts may also be of different types.
+
+We owe to Herbst the important discovery that the eyes of crayfishes,
+after being cut off, will be regenerated in the proper way, if the optic
+ganglion is present, but that an antenna will arise in their place
+if this ganglion has also been removed. There must in this case be
+some unknown influence of the formative kind on which depends, if not
+regeneration itself, at least its special character.
+
+In other cases there seems to be an influence of the central nervous
+system on the regenerative power in general. Amphibia, for instance,
+are said to regenerate neither their legs (Wolff), nor their tail
+(Godlewski), if the nervous communications have been disturbed. But
+in other animals there is no such influence; and in yet others, as
+for instance, in Planarians, it must seem doubtful at present whether
+the morphogenetic influence of the nervous system upon processes of
+restoration is more than indirect; the movements of the animal, which
+become very much reduced by the extirpation of the ganglia, being one of
+the main conditions of a good regeneration.
+
+Of course, all we have said about the importance of special materials
+in the ripe germ, as bearing on specifically localised organisations,
+might be discussed again in our present chapter, and our intimate
+polar-bilateral structure of germs may also be regarded as embracing
+formative stimuli, at any rate as far as the actual poles of this
+structure are concerned. This again would bring us to the problem of
+so-called “polarity” in general, and to the “inversion” of polarity,
+that is to a phenomenon well known in plants and in many hydroids and
+worms, viz., that morphogenetic processes, especially of the type of
+restitutions, occur differently, according as their point of origin
+represents, so to speak, the positive or the negative, the terminal or
+the basal end of an axis, but that under certain conditions the reverse
+may also be the case. But a fuller discussion of these important facts
+would lead us deeper and deeper into the science of morphogenesis
+proper, without being of much use for our future considerations.
+
+And so we may close this section[43] on formative stimuli or “causes”
+of morphogenesis by shortly adding, more on account of its factual
+than of its logical interest, that the phenomenon of the determination
+of sex,[44] according to the latest researches, seems to depend on
+cytological events occurring in the very earliest embryonic stages,
+say even before ontogeny, and not on formative stimuli proper[45]: it
+seems, indeed, as if the sexual products themselves would account for
+the sex of the individual produced by them, particularly if there were
+differences in their chromatin.[46]
+
+[43] A full analysis of the subject would not only have to deal with
+formative stimuli as inaugurating morphogenetic processes, but also with
+those stimuli which terminate or stop the single acts of morphogenesis.
+But little is actually known about this topic, and therefore the reader
+must refer to my other publications. I will only say here, that the end
+of each single morphogenetic act may either be determined at the very
+beginning or occur as an actual stopping of a process which otherwise
+would go on for ever and ever; in the first case some terminating
+factors are included in the very nature of the morphogenetic act itself.
+
+[44] A full account of the present state of the subject will be found in
+Morgan’s *Experimental Zoology*, New York, 1907.
+
+[45] But there certainly exist many formative relations between the real
+sexual organs and the so-called secondary sexual characters. Herbst has
+given a full analytical discussion of all that is known on this subject;
+but the facts are much more complicated than is generally supposed, and
+do not lend themselves therefore to short description. See also Foges,
+*Pflüger’s Arch.* 93, 1902.
+
+[46] It seems that in some cases (*Dinophilus*, certain Arthropods)
+the sexual products are invariably determined as “arrenogennetic”
+or as “thelygennetic” (Wilson, *Journ. Exp. Zool.* ii. and iii.
+1905-6), whilst in others (Amphibia) the state of maturation or
+“super”-maturation determines the sex of the future organism (R.
+Hertwig, *Verh. D. Zool. Ges.* 1905-7).
+
+
+δ. THE MORPHOGENETIC HARMONIES
+
+Let us now turn again to considerations of a more abstract kind: we have
+become acquainted with some morphogenetic interactions among the parts
+of a developing embryo; and, indeed, we can be sure that there exist far
+more of such interactions than we know at present.
+
+But it is far from being true that the development of each embryonic
+part depends on the existence or development of every other one.
+
+On the contrary, it is a very important and fundamental feature
+of organogenesis that it occurs in separate lines, that is to
+say, in lines of processes which may start from a common root, but
+which are absolutely independent of one another in their manner of
+differentiation. Roux has coined the term “self-differentiation” to
+denote this phenomenon, and we admit that this term may be conveniently
+used for the purpose, if only it can be kept in mind that its sense is
+always relative, and that it is also negative. Suppose a part, *A*,
+shows the phenomenon of self-differentiation: this means that the
+further development of *A* is not dependent on certain other parts,
+*B*, *C*, and *D*; it does *not* mean at all that *A* has not been
+formatively dependent on some other parts, *E* or *F* at the time of
+its first appearance, nor does it imply that there might not be many
+formative actions among the constituents of *A* itself.
+
+We indeed are entitled to say that the ectoderm of Echinus shows
+“self-differentiation” with regard to the endoderm; it acquires its
+mouth, for instance, as has been shown by experiment, even in cases
+where no intestine is present at all (Fig. 10); but ectoderm and
+endoderm both are formatively dependent on the intimate and the material
+organisation of the blastoderm. It further seems from the most recent
+experiments that the nerves and the muscles of the vertebrates are
+independent of each other in their differentiation, but that their fate
+is probably determined by formative processes in the very earliest
+stages of ontogeny.
+
+[Illustration: Fig. 10.--Pluteus-larva of Sphaerechinus.
+
+The Intestine (i) is developed outside instead of inside (by means of
+raising the temperature); but the mouth (r) is formed in its normal
+place. S = Skeleton.]
+
+The phenomenon of self-differentiation, properly understood, now may
+help to the discovery of one most general character of all development.
+If the phenomenon of self-differentiation really occurs in ontogeny
+in its most different aspects, and if, on the other hand, in spite
+of this relative morphogenetic independence of embryonic parts, the
+resulting organism is one whole in organisation and in function, some
+sort of *harmony of constellation*, as it may properly be styled, must
+be said to be one of the most fundamental characters of all production
+of individual form. In establishing this harmony we do nothing more
+than describe exactly what happens: the harmony is shown by the fact
+that there is a whole organism at the end, in spite of the relative
+independence of the single events leading to it.
+
+But still another sort of harmony is revealed in morphogenesis, by an
+analysis of the general conditions of the formative actions themselves.
+In order that these actions may go on properly the possibility must be
+guaranteed that the formative causes may always find something upon
+which to act, and that those parts which contain the potencies for the
+next ontogenetic stage may properly receive the stimuli awaking these
+potencies: otherwise there would be no typical production of form at
+all. This, the second species of harmonious relations to be described in
+ontogeny, may be called *causal harmony*; the term simply expresses the
+unfailing relative condition of formative causes and cause-recipients.
+
+Finally, in *functional harmony* we have an expression descriptive
+of the unity of organic function, and so we may state, as the latest
+result of our analytical theory of development up to this point, that
+individual morphogenesis is marked by a *threefold harmony* among its
+parts.
+
+
+ε. ON RESTITUTIONS[47]
+
+[47] Driesch, *Die organischen Regulationen*, Leipzig, 1901; Morgan,
+*Regeneration*, New York, 1901.
+
+At this stage we leave for a while our analytical studies of ontogeny
+proper. We must not forget that typical ontogenesis is not the only form
+in which morphogenesis can occur: the organic form is able to restore
+disturbances of its organisation, and it certainly is to be regarded as
+one of the chief problems of analytical morphogenesis to discover the
+specific and real stimulus which calls forth the restoring processes.
+For simply to say that the disturbance is the cause of the restoration
+would be to evade the problem instead of attacking it. But there are
+still some other problems peculiar to the doctrine of restitutions.
+
+*A few Remarks on Secondary Potencies and on Secondary Morphogenetic
+Regulations in General*
+
+We have only briefly mentioned in a previous chapter that there
+exist many kinds of potencies of what we call the secondary or truly
+restitutive type, and that their distribution may be most various and
+quite independent of all the potencies for the primary processes
+of ontogeny proper. Let us first add a few words about the concept
+of “secondary restitution” and about the distribution of secondary
+potencies in general.
+
+Primary ontogenetic processes founded upon primary potencies may *imply*
+regulation, or more correctly, restitution in many cases: so it is,
+when fragments of the blastula form the whole organism, or when the
+mesenchyme cells of Echinus reach their normal final position by an
+attraction on the part of specific localities of the ectoderm in spite
+of a very abnormal original position enforced upon them by experiment.
+In these cases we speak of primary regulations or restitutions;
+disturbances are neutralised by the very nature of the process in
+question. We speak of secondary restitution whenever a disturbance
+of organisation is rectified by processes foreign to the realm of
+normality; and these abnormal lines of events are revealed to us in the
+first place by the activity of potencies which remain latent in ontogeny
+proper.
+
+We know already that a certain kind of secondary restitution has
+been discovered lately, very contradictory to the theoretical views
+of Weismann; the process of restoration being carried out not by any
+definite part of the disturbed organisation, but by all the single
+elements of it. The problem of the distribution of secondary potencies
+in these cases of so-called “re-differentiation” is to form our special
+study in the next chapter. In all other cases restoration processes
+start from specific localities; if they occur on the site of the
+wound which caused the disturbance, we speak of regeneration; if they
+occur at some distance from the wound, we call them adventitious
+processes. Besides these three types of processes of restitution there
+may be mentioned a fourth one, consisting in what is generally called
+compensatory hypertrophy; the most simple case of such a compensatory
+process is when one of a pair of organs, say a kidney, becomes larger
+after the other has been removed.[48] Finally, at least in plants, a
+change of the directive irritability, of so-called “geotropism” for
+instance, in certain parts may serve to restore other more important
+parts.
+
+[48] But real compensatory differentiation occurs in the cases of
+so-called “hypertypy” as first discovered by Przibram and afterwards
+studied by Zeleny: here the two organs of a pair show a different degree
+of differentiation. Whenever the more specialised organ is removed the
+less developed one assumes its form. Similar cases, which might simply
+be called “compensatory heterotypy,” are known in plants, though only
+relating to the actual fate of undifferentiated “Anlagen” in these
+organisms. A leaf may be formed out of the Anlage of a scale, if all the
+leaves are cut off, and so on.
+
+In two of these general types of restitution, in regeneration proper and
+in the production of adventitious organs, the potencies which underlie
+these processes may be said to be “complex.” It is a complicated series
+of events, a proper morphogenesis in itself, for which the potency
+has to account, if, for instance, a worm newly forms its head by
+regeneration, or if a plant restores a whole branch in the form of an
+adventitious bud.
+
+Such generalisations as are possible about the distribution of complex
+potencies are reserved for a special part of our future discussion.
+
+Secondary restitution is always, like ontogeny, a process of
+morphogenesis, and therefore all the questions about single formative
+stimuli, and about internal and external conditions or means, occur
+again. But of course we cannot enter into these problems a second time,
+and may only say that, especially in regeneration proper, the specific
+type of the regenerative formation of any part may differ very much from
+the ontogenetic type of its origin: the end of both is the same, but the
+way can be even fundamentally different in every respect.
+
+*The Stimuli of Restitutions*[49]
+
+[49] For a fuller analysis compare my opening address delivered before
+the section of “Experimental Zoology” at the Seventh Zoological
+Congress, Boston, 1907: “The Stimuli of Restitutions” (see Proceedings
+of that Congress).
+
+But now we turn to the important question: what is the precise
+stimulus[50] that calls forth processes of restitution; or, in other
+words, what must have happened in order that restitution may occur?
+
+[50] The problem of the stimulus of a secondary restitution as a
+whole must not be confused with the very different question, what the
+single “formative stimuli” concerned in the performance of a certain
+restitutive act may be. With regard to restitution as a *whole* these
+single “formative stimuli” might properly be said to belong to its
+“internal means”--in the widest sense of the word.
+
+That the operation in itself, by its removing of mechanical obstacles,
+cannot be the true stimulus of any restitutions, is simply shown by all
+those restitutions that do not happen at the place of the wound. If we
+took a narrower point of view, and if we only considered regeneration
+proper from the wound itself, we might probably at first be inclined to
+advocate the doctrine that the removing of some obstacles might in fact
+be the stimulus to the process of restoration; but, even then, why is
+it that just what is wanted grows out? Why is there not only growth,
+but specific growth, growth followed by specification? The removing
+of an obstacle could hardly account for that. But, of course, taking
+account of all the adventitious restitutions--that is, all restorations
+not beginning at the wound itself--the theory that the removing of
+obstacles is the stimulus to restoration becomes, as we have said, quite
+impossible.[51]
+
+[51] T. H. Morgan is very right in stating that, in regeneration, the
+“obstacle” itself is newly formed by the mere process of healing,
+previous to all restitution, and that true restitution happens all the
+same.
+
+But where then is the stimulus to be found? There is another rather
+simple theory of the “Auslösung” of restitutions,[52] which starts
+from the phenomena of compensatory hypertrophy and some occurrences
+among plants. The removal of some parts of the organism, it is said,
+will bring its other parts into better conditions of nutrition, and
+therefore these parts, particularly if they are of the same kind, will
+become larger. Granted for the moment that such a view may hold in cases
+when one of a pair of glands becomes larger after the other has been
+removed, or when pruning of almost all the leaves of a tree leads to the
+rest becoming larger, it certainly must fail to explain the fact that
+in other cases true *new* formations may arise in order to restore a
+damaged part, or that the latter may be regenerated in its proper way.
+For *merely quantitative* differences in the mixture of the blood or of
+the nourishing sap in plants can never be a sufficient reason for the
+highly typical and *qualitative* structure of newly-formed restitutions.
+And even in the most simple cases of a mere increase in the size of
+some parts, that is, in the simplest cases of so-called compensatory
+hypertrophy,[53] it is at least doubtful, if not very improbable, that
+the compensation is accomplished in such a purely passive way, because
+we know that in other cases it is usually the growth of the young parts
+that actively attracts the nourishment: there is first differentiation
+and growth, and *afterwards* there is a change in the direction of the
+nourishing fluids.
+
+[52] I merely mention here the still “simpler” one--applicable of course
+to regeneration proper exclusively--that for the simple reason of being
+“wounded,” *i.e.* being a surface open to the medium, the “wound” brings
+forth all that is necessary to complete the organism.
+
+[53] That compensatory hypertrophy cannot be due to “functional
+adaptation”--to be analysed later on--was proved by an experiment of
+Ribbert’s. Compensation may occur before the function has made its
+appearance, as was shown to be the case in the testicles and mammae of
+rabbits. (*Arch. Entw. Mech.* 1, 1894, p. 69.)
+
+The process of true regeneration, beginning at the locality of the wound
+itself, has been shown by Morgan, even as regards its rate, to occur
+quite irrespectively of the animal being fed or not.[54] There could
+hardly be a better demonstration of the fundamental fact that food
+assists restitution, but does not “cause” it in any way.
+
+[54] At any given time only the absolute size of the regenerated part is
+greater in animals which are well fed; the degree of differentiation is
+the same in all. Zeleny has found that, if all five arms of a starfish
+are removed, each one of them will regenerate more material in a given
+time than it would have done if it alone had been removed. But these
+differences also only relate to absolute size and not to the degree
+of differentiation. They possibly may be due in fact to conditions of
+nourishment, but even here other explanations seems possible (Zeleny,
+*Journ. exp. Zool.* 2, 1905).
+
+But in spite of all we have said, there seems to be some truth in
+regarding the nutritive juices of animals and plants as somehow
+connected with the stimulus of restitutions: only in this very cautious
+form, however, may we make the hypothesis. It has been shown for both
+animals and plants, that morphogenesis of the restitutive type may be
+called forth even if the parts, now to be “regenerated” have not been
+actually removed; *e.g.* in the so-called super-regeneration of legs
+and tails in Amphibia, of the head in Planarians, of the root-tip in
+plants and in some other cases. Here it has always been a disturbance
+of the normal connection of some parts with the rest of the organism
+which proved to be the reason of the new formation. This shows that
+something to do with the communication among parts is at least connected
+with restitution, and this communication may go on either by the unknown
+action of specific tissues or by the aid of the blood or sap.[55] But
+in what this change or break of specific communication consists, is
+absolutely unknown. One might suppose that each part of the organisation
+constantly adds some sort of ferment to the body fluids outside or
+inside the cells, that the removing of any part will change the
+composition of these fluids in this particular respect, and that this
+change acts as a sort of communication to summon the restituting parts
+of the whole to do their duty.[56]
+
+[55] For a good discussion of “super-regeneration” in the roots of
+plants see Němec, *Studien über die Regeneration*, Berlin, 1905. Goebel
+and Winkler have succeeded in provoking the “restitution” of parts which
+were not removed at all by simply stopping their functions (leaves of
+certain plants were covered with plaster, etc.). (*Biol. Centralbl.* 22,
+1902, p. 385; *Ber. Bot. Ges.* 20, 1902, p. 81.) A fine experiment is
+due to Miehe. The alga *Cladophora* was subjected to “plasmolysis,” each
+cell then formed a new membrane of its own around the smaller volume of
+its protoplasm; after that the plants were brought back to a medium of
+normal osmotic pressure, and then each single cell grew up into a little
+plant (all of them being of the same polarity!). Two questions seem
+to be answered by this fact: loss of communication is of fundamental
+importance to restitution, and the removal of mechanical obstacles plays
+no part in it, for the mechanical resistances were the same at the end
+of the experiment as they had been at the beginning. (*Ber. Bot. Ges.*
+23, 1905, p. 257.) For fuller analysis of all the problems of this
+chapter see my Organische Regulationen, my reviews in the *Ergebnisse
+der Anatomie und Entwickelungsgeschichte*, vols. viii. xi. xiv., and
+my Boston address mentioned above. Compare also Fitting, *Ergebn. d.
+Physiol.* vols. iv. and v.
+
+[56] The so-called “inner secretion” in physiology proper would offer a
+certain analogy to the facts assumed by such an hypothesis. Compare the
+excellent summary given by E. Starling at the seventy-eighth meeting of
+the German “Naturforscherversammlung,” Stuttgart, 1906.
+
+But I see quite well that such a theory is very little satisfactory;
+for what has to be done in restitution in each case is not a simple
+homogeneous act, for which one special material might account, but is
+a very complicated work in itself. It was the defect of the theory of
+“organ-forming substances” as advocated by Sachs, that it overlooked
+this point.
+
+So all we know about the proper stimuli of restitutions is far from
+resting on any valid grounds at all; let us not forget that we are
+here on the uncertain ground of what may be called the newest and
+most up-to-date branch of the physiology of form. No doubt, there
+will be something discovered some day, and the idea of the “whole” in
+organisation will probably play some part in it. But in what manner that
+will happen we are quite unable to predict.
+
+This is the first time that, hypothetically at least, the idea of the
+whole has entered into our discussion. The same idea may be said to
+have entered it already in a more implicit form in the statement of the
+threefold harmony in ontogeny.
+
+Let us now see whether we can find the same problem of the “whole”
+elsewhere, and perhaps in more explicit and less hypothetical form.
+Let us see whether our analytical theory of development is in fact as
+complete as it seemed to be, whether there are no gaps left in it which
+will have to be filled up.
+
+
+3. THE PROBLEM OF MORPHOGENETIC LOCALISATION
+
+α. THE THEORY OF THE HARMONIOUS-EQUIPOTENTIAL SYSTEM
+
+FIRST PROOF OF THE AUTONOMY OF LIFE
+
+We have come to the central point of the first part of these lectures;
+we shall try in this chapter to decide a question which is to give life
+its place in Nature, and biology its place in the system of sciences.
+One of the foundation stones is to be laid upon which our future
+philosophy of the organism will rest.
+
+
+*The General Problem*
+
+Our analytical theory of morphogenesis has been founded upon three
+elementary concepts: the prospective potency, the means, and the
+formative stimulus. Its principal object has been to show that all
+morphogenesis may be resolved into the three phenomena expressed by
+those concepts; in other terms, that morphogenesis may be proved to
+consist simply and solely of what is expressed by them. Have we indeed
+succeeded in attaining this object? Has nothing been left out? Is it
+really possible to explain every morphogenetic event, at least in the
+most general way, by the aid of the terms potency, means, and stimulus?
+
+All of these questions are apt to lead us to further considerations.
+Perhaps these considerations will give us a very clear and simple result
+by convincing us that it is indeed possible to analyse morphogenesis in
+our schematic way.
+
+But if the answer were a negative one? What would that suggest?
+
+The full analysis of morphogenesis into a series of single formative
+occurrences, brought about by the use of given means and on the basis of
+given potencies, might assure us, perhaps, that, though not yet, still
+at some future time, a further sort of analysis will be possible: the
+analysis into the elemental facts studied by the sciences of inorganic
+nature. The organism might prove to be a machine, not only in its
+functions but also in its very origin.
+
+But what are we to say if even the preliminary analysis, which possibly
+might lead to such an ultimate result, fails?
+
+Let us then set to work. Let us try to consider most carefully the topic
+in which our concept of the formative cause or stimulus may be said
+to be centred, the *localisation* of all morphogenetic effects. Is it
+always possible in fact to account for the typical localisation of every
+morphogenetic effect by the discovery of a single specific formative
+stimulus? You will answer me, that such an analysis certainly is not
+possible at present. But I ask you again, are there any criteria that it
+is possible, at least in principle; or are there any criteria which will
+render such an aim of science impossible for all future time?
+
+
+*The Morphogenetic “System”*
+
+We know from our experimental work that many, if not all, of the
+elementary organs in ontogeny show one and the same prospective
+potency distributed equally over their elements. If we now borrow a
+very convenient term from mechanics, and call any part of the organism
+which is considered as a unit from any morphogenetic point of view, a
+morphogenetic “*system*,” we may sum up what we have learnt by saying
+that both the blastoderm of the echinoderms, at least around its
+polar axis, and also the germ-layers of these animals, are “systems”
+possessing an equal potentiality in all of their elements, or, in short,
+that they are *equipotential systems*.
+
+But such a term would not altogether indicate the real character of
+these systems.
+
+Later on we shall analyse more carefully than before the distribution
+of potencies which are the foundation both of regeneration proper and
+of adventitious growth, and then we shall see that, in higher plants
+for instance, there is a certain “system” which may be called the
+organ proper of restitutions, and which also in each of its elements
+possesses the same restoring potency; I refer to the well-known cambium.
+This cambium, therefore, also deserves the name of an “equipotential
+system.” But we know already that its potencies are of the complex
+type, that they consist in the faculty of producing the *whole*, of
+such a complicated organisation as a branch or a root, that the term
+“equipotential system” is here only to signify that such a complicated
+unit may arise out of each of the cells of the cambium.
+
+The potencies we have been studying in the blastula or gastrula of
+echinoderms are not of the complex type: our systems are equipotential
+to the extent that each of their elements may play every *single* part
+in the totality of what will occur in the whole system; it is to
+this *single* part that the term “function of the position” relates.
+We therefore might call our systems equipotential systems with single
+potencies; or, more shortly, singular-equipotential systems.
+
+But even this terminology would fail to touch precisely the very
+centre of facts: it is not only the simplicity or singularity of
+their potencies which characterises the rôle of our systems in
+morphogenesis,[57] but far more important with respect to the production
+of form are two other leading results of the experimental researches.
+The proper act to be performed by every element in each actual case is
+in fact a single one, but the potency of any element as such consists
+in the possibility of many, nay of indefinitely many, single acts:
+that then might justify us in speaking of our systems as “indefinite
+equipotential,” were it not that another reason makes another title seem
+still more preferable. There are indeed indefinite singular potencies at
+work in all of our systems during ontogeny: but the sum of what happens
+to arise in every case out of the sum of the single acts performed by
+all of the single equipotential cells is not merely a sum but a unit;
+that is to say, there exists a sort of harmony in every case among the
+*real products* of our systems. The term *harmonious-equipotential
+system* therefore seems to be the right one to denote them.
+
+[57] The name of singular-equipotential systems might also be applied
+to elementary organs, the single potencies of which are awaked to
+organogenesis by specific formative stimuli from without; but that is
+not the case in the systems studied in this chapter.
+
+We now shall try first to analyse to its very extremes the meaning of
+the statement that a morphogenetic system is harmonious-equipotential.
+
+
+*The “Harmonious-Equipotential System”*
+
+We have an ectoderm of the gastrula of a starfish here before us; we
+know that we may cut off any part of it in any direction, and that
+nevertheless the differentiation of the ectoderm may go on perfectly
+well and result in a typical little embryo, which is only smaller in
+its size than it would normally be. It is by studying the formation of
+the highly complicated ciliary band, that these phenomena can be most
+clearly understood.
+
+Now let us imagine our ectoderm to be a cylinder instead of being
+approximately a sphere, and let us imagine the surface of this cylinder
+unrolled. It will give us a plane of two definite dimensions, *a* and
+*b*. And now we have all the means necessary for the analytical study of
+the differentiation of an harmonious-equipotential system.
+
+Our plane of the dimensions *a* and *b* is the basis of the normal,
+undisturbed development; taking the sides of the plane as fixed
+localities for orientation, we can say that the actual fate, the
+“prospective value” of every element of the plane stands in a fixed and
+definite correlation to the length of two lines, drawn at right angles
+to the bordering lines of the plane; or, to speak analytically, there
+is a definite actual fate corresponding to each possible value of *x*
+and of *y*. Now, we have been able to state by our experimental work,
+that the prospective value of the elements of our embryonic organ is not
+identical with their “prospective potency,” or their possible fate, this
+potency being very much richer in content than is shown by a single case
+of ontogeny. What will be the analytical expression of such a relation?
+
+Let us put the question in the following way: on what factors does
+the fate of any element of our system depend in all possible cases
+of development obtainable by means of operations? We may express our
+results in the form of an equation:--
+
+ *p.v. (X) = f( ... )*
+
+*i.e.* “the prospective value of the element *X* is a function of
+...”--of what?
+
+We know that we may take off any part of the whole, as to quantity, and
+that a proportionate embryo will result, unless the part removed is of
+a very large size. This means that the prospective value of any element
+certainly depends on, certainly is a function of, the *absolute size*
+of the actually existing part of our system in the particular case. Let
+*s* be the absolute size of the system in any actual experimental case
+of morphogenesis: then we may write *p.v. (X) = f(s ... )*. But we
+shall have to add still some other letter to this *s*.
+
+The operation of section was without restriction either as to the
+amount of the material removed from the germ, or as to the direction of
+the cut. Of course, in almost every actual case there will be both a
+definite size of the actual system and a definite direction of the cut
+going hand-in-hand. But in order to study independently the importance
+of the variable direction alone, let us imagine that we have isolated
+at one time that part of our system which is bounded by the lines *a_1
+b_1*, and at another time an equal amount of it which has the lines
+*a_2 b_2* as its boundaries. Now since in both cases a typical small
+organism may result on development, we see that, in spite of their equal
+size the prospective value of every element of the two pieces cut
+out of the germ may vary even in relation to the direction of the cut
+itself. Our element, *X*, may belong to both of these pieces of the same
+size: its actual fate nevertheless will be different. Analytically, it
+may be said to change in correspondence to the actual position of the
+actual boundary lines of the piece itself with regard to the fundamental
+lines of orientation, *a* and *b*; let this actual position be expressed
+by the letter *l*, *l* marking the distance of one[58] of the actual
+boundary lines of our piece from *a* or *b*: then we are entitled to
+improve our formula by writing *p.v. (X) = f(s, l ... )* (Fig.
+11).
+
+[58] The distance of the other boundary line from *a* or *b* would be
+given by the value of *s*.
+
+[Illustration: Fig. 11.--Diagram to show the Characteristics of an
+“Harmonious-equipotential System.”
+
+The element *X* forms part of the systems *a b* or *a_1 b_1* or
+*a_2 b_2*; its prospective value is different in each case.]
+
+But the formula is not yet complete: *s* and *l* are what the
+mathematicians call variables: they may have any actual value and there
+will always be a definite value of *p.v.*, *i.e.* of the actual fate
+which is being considered; to every value of *s* and *l*, which as
+we know are independent of each other, there corresponds a definite
+value of the actual prospectivity. Now, of course, there is also a
+certain factor at work in every actual case of experimental or normal
+development, which is *not* a variable, but which is the same in all
+cases. This factor is a something embraced in the prospective potency
+of our system, though not properly identical with it.
+
+The prospective potency of our system, that is to say of each of its
+elements, is the sum total of what can be done by all; but the fact
+that a typically proportionate development occurs in every possible
+case, proves that this sum comes into account, not merely as a sum,
+but as a sort of order: we may call this order the “relation of
+localities in the absolutely normal case.” If we keep in mind that the
+term “prospective potency” is always to contain this order, or, as we
+may also call it, this “relative proportionality,” which, indeed, was
+the reason for calling our systems “harmonious,” then we may apply it
+without further explanation in order to signify the *non-variable*
+factor on which the prospective value of any element of our systems
+depends, and, if we denote the prospective potency, embracing order,
+by the letter *E*, we are now able to complete our formula by saying
+*p.v. (X) = f(s, l, E)*. So far the merely analytical study of the
+differentiation of harmonious-equipotential systems.[59]
+
+[59] A far more thorough analysis of this differentiation has been
+attempted in my paper, “Die Localisation morphogenetischer Vorgänge. Ein
+Beweis vitalistischen Geschehens,” Leipzig, 1899.
+
+
+*Instances of “Harmonious-Equipotential Systems”*
+
+We must try at first to learn a few more positive facts about our
+systems, in order that we may know how important is the part which they
+play in the whole animal kingdom, and in order that our rather abstract
+analysis may become a little more familiar to us. We know already that
+many of the elementary morphogenetic organs have been really proved to
+be harmonious-equipotential systems, and that the same probably is true
+of many others; we also know that the immature egg of almost all animals
+belongs to this type, even if a fixed determination of its parts may
+be established just after maturation. Moreover, we said, when speaking
+about some new discoveries on form-restitution, that there are many
+cases in which the processes of restitution do not proceed from single
+localities, the seat of complex potencies in the organism, but in which
+each *single* part of the truncated organism left by the operation has
+to perform one *single* act of restoration, the full restitution being
+the result of the totality of all. These cases must now be submitted to
+a full analysis.
+
+All of you have seen common sea-anemones or sea-roses, and many of you
+will also be familiar with the so-called hydroid polyps. *Tubularia*
+is one genus of them: it looks like a sea-anemone in miniature placed
+on the top of a stem like a flower. It was known already to Allman
+that *Tubularia* is able to restore its flower-like head when that
+is lost, but this process was taken to be an ordinary regeneration,
+until an American zoologist, Miss Bickford, succeeded in showing that
+there was no regeneration process at all, in the proper sense of the
+word, no budding of the missing part from the wound, but that the new
+tubularian head was restored by the combined work of many parts of the
+stem. Further analysis then taught us that *Tubularia* indeed is to be
+regarded as the perfect type of an harmonious-equipotential system: you
+may cut the stem at whatever level you like: a certain length of the
+stem will always restore the new head by the co-operation of its parts.
+As the point of section is of course absolutely at our choice, it is
+clear, without any further discussion, that the prospective value of
+each part of the restoring stem is a “function of its position,” that
+it varies with its distance from the end of the stem; and so at once
+we discover one of the chief characteristics of our systems. But also
+the second point which enters into our formula can be demonstrated in
+*Tubularia*: the dependence of the fate of every element on the actual
+size of the system. You would not be able to demonstrate this on very
+long stems, but if you cut out of a *Tubularia* stem pieces which are
+less than ten millimetres in length, you will find the absolute size
+of the head restored to be in close relation to the length of the stem
+piece, and this dependence, of course, includes the second sort of
+dependence expressed in our formula.
+
+The figures will serve to show you a little more concretely what has
+been described. The head of *Tubularia* consists of a sort of broad base
+with a thin proboscis upon it, both bearing a large number of tentacles;
+these tentacles are the first things to be seen as primordia (“Anlagen”)
+in the process of restitution. You notice two rings of longitudinal
+lines inside the stem; the lines will become walls and then will
+separate from the stem until they are only connected with it at their
+basal ends; the new tentacles are ready as soon as that has happened,
+and a process of growth at the end will serve to drive the new head out
+of the so-called perisarc or horny skeleton, which surrounds the stem.
+By comparing the two figures, 12 *e*, and *g*, you easily find out that
+the absolute lengths of the two tentacle rings are very different, and
+that both are in proportion[60] to the actual size of the stem (Fig. 12).
+
+[60] This statement is *not strictly* correct for *Tubularia*. I found
+(*Archiv f. Entwickelungsmechanik*, ix. 1899), that a reduction of the
+length of the stem is always followed by a reduction of the size of the
+hydranth-primordium, but there is no real proportionality between them.
+It is only for theoretical simplification that a strict proportionality
+is assumed here, both in the text and the diagram. But there is an
+almost strict proportionality in all cases of “closed forms.”
+
+[Illustration: Fig. 12.--Tubularia.
+
+*a.* Diagram of the “Hydranth,” with its short and long tentacles.
+
+*b.* Restitution of a new hydranth inside the perisarc (*p*).
+
+*c.* The same--later stage; the tentacles are complete; the whole
+hydranth will be driven out of the perisarc by a process of growth that
+occurs at the locality marked ⬆.
+
+*d.* A stem of *Tubularia* cut either at *a_1 b_1* or at *a_2 b_2*,
+or at *a_1 c*.
+
+*e.* Position of tentacles in the piece cut at *a_1 b_1*.
+
+*f.* Position of tentacles in the piece cut at *a_2 b_2*,
+which is equal in length to *a_1 b_1*.
+
+*g.* Position of tentacles in the piece cut at *a_1 c*,
+which is half as long as *a_1 b_1*.]
+
+So we find our formula *p.v. (X) = f(s, l, E)* very well
+illustrated in *Tubularia*. The formula indeed may help us to predict,
+in any case, where a certain part of the polyp’s organisation is
+to originate, at least if we know all that is included under our
+letter *E*, *i.e.* the normal proportion of our form. Of course such
+prediction would not have much practical importance in all our cases of
+morphogenesis, but nevertheless I should like to state here that it is
+possible; for many scientific authors of recent times have urged the
+opinion that prediction of, and domination over, what will happen, can
+be the only true aims of sciences at all. I myself judge these aims to
+be of second or third-rate importance only, but, if they may be reached
+by what our purely theoretical study teaches, so much the better.
+
+Another very typical case of a morphogenetic system of the harmonious
+type is supplied by the phenomena of restoration in the ascidian
+*Clavellina*. I cannot fully describe the organisation of this form
+(Fig. 13a), and it must suffice to say that it is very complicated,
+consisting of two very different chief parts, the branchial apparatus
+and the so-called intestinal sac; if these two parts of the body of
+*Clavellina* are separated one from the other, each may regenerate the
+other in the typical way, by budding processes from the wound. But, as
+to the branchial apparatus, there may happen something very different:
+it may lose almost all of its organisation and become a small white
+sphere, consisting only of epithelia corresponding to the germ-layers,
+and of mesenchyme between them, and then, after a certain period of
+rest, a new organisation will appear. Now this new organisation is
+not that of a branchial apparatus but represents a very small but
+complete ascidian (Fig. 13). Such a fact certainly seems to be very
+important, not to say very surprising; but still another phenomena may
+be demonstrated on the animal which seems to be even more important. You
+first isolate the branchial apparatus from the other part of the body,
+and then you cut it in two, in whatever direction you please. Provided
+they survive and do not die, as indeed many of them do, the pieces
+obtained by this operation will each lose their organisation, as did the
+whole branchial apparatus, and then will each acquire another one, and
+this new organisation is also that of a *complete* little *Clavellina*.
+So we see that not only is the branchial apparatus of our animal capable
+of being transformed into a whole animal by the co-operative work of
+all its parts, but even each part of it may be transformed into a small
+*whole*, and it is quite at our disposal how large this part shall be,
+and what sort of a fragment of the original branchial apparatus it shall
+represent.
+
+[Illustration: Fig. 13.--Clavellina.
+
+*a.* Diagram of the normal animal: *E* and *J* = openings; *K* =
+branchial apparatus; *D* = intestine; *M* = stomach; *H* = heart.
+
+*b.* The isolated branchial apparatus.
+
+*c-e.* Different stages of reduction of the branchial apparatus.
+
+*f.* The new *whole* little ascidian.]
+
+We could hardly imagine a better instance of an harmonious-equipotential
+system.
+
+I cannot give you a description of all the other types of our systems
+subservient to restitution, and I can only mention here that the common
+hydra and the flatworm *Planaria* are very fine examples of them. But
+to one special case of harmonious equipotentiality you must allow me to
+direct your further attention.
+
+It has been known for many years that the Protozoa are also capable of
+a restoration of their form and organisation after disturbances, if at
+least they contain a certain amount of their nuclear substance. This
+process of restoration used to be regarded as belonging to the common
+type of regeneration proper, until T. H. Morgan succeeded in showing
+that in the genus *Stentor* it follows just the very lines which we know
+already from our study of embryonic organs or from *Tubularia*; that
+an harmonious-equipotential system is at the basis of what goes on.
+Now, you know that all Protozoa are but one highly organised cell: we
+have therefore here an instance where the so-called “elements” of our
+harmonious-morphogenetic system are not cells, but something inside of
+cells; and this feature must appear to be of very great moment, for it
+first shows, as we have already pointed out on another occasion, that
+morphogenesis is not dependent on cell-division, and it states at the
+same time that our concept of the harmonious-equipotential system may
+cover a very great area--that, in fact, it is a scheme of a very wide
+extent.
+
+
+*The Problem of the Factor* E
+
+We turn back again to considerations of a more abstract form. We left
+our analysis of the differentiation of the harmonious-equipotential
+systems, and particularly of the phenomena of localisation during this
+differentiation, at the point where we had succeeded in obtaining an
+equation as the expression of all those factors on which the prospective
+value, the actual fate, of any element of our systems depends, *p.v. (X)
+= f(s, l, E)* was the short expression of all the relations involved;
+*s* and *l*, the absolute size of the system and the relative position
+of the element with respect to some fixed points, were independent
+variables; *E* was a constant, namely, the prospective potency, with
+special regard to the proportions embraced by it.
+
+We shall now study the significance of the factor *E*.
+
+What does this *E* mean? Is it a short expression merely for an actual
+sum of elemental agents having a common resultant? And, if so, of what
+kind are these agents? Or what may *E* mean, if it can be shown *not* to
+be a short sign for a mere sum?
+
+
+*No Explanation Offered by “Means” or “Formative Stimuli”*
+
+For practical purposes it seems better if we modify the statement of our
+question. Let us put it thus: *E* is one of the factors responsible,
+among variables, for the localisation of organic differentiation;
+what then do we actually know about the causal factors which play a
+localising part in organogenesis? We, of course, have to look back to
+our well-studied “formative stimuli.” These stimuli, be they “external”
+or “internal,” come from without with respect to the elementary organ
+in which any sort of differentiation, and therefore of localisation,
+occurs: but in our harmonious systems no localising stimulus comes from
+without, as was the case, for instance, in the formation of the lens of
+the eye in response to the optical vesicle touching the skin. We know
+absolutely that it is so, not to speak of the self-evident fact that the
+general “means” of organogenesis have no localising value at all.[61]
+
+[61] One might object here that in a piece of a *Tubularia* stem, for
+instance, the tissues are in direct contact with the sea-water at
+the two points of the wounds only, and that at these very points a
+stimulus might be set up--say by a process of diffusion--which gradually
+decreases in intensity on its way inward. And a similar argument might
+apply to the small but whole blastula of Echinus, and to all other
+cases. But, in the first place, stimuli which only differ in intensity
+could hardly call forth the typical and typically localised single
+features realised in differentiation. On the other hand--and this will
+overthrow such an hypothesis completely--the dependence of the single
+localised effects in every case on the *absolute size* of the fragment
+or piece chosen for restoration renders quite impossible the assumption
+that all the singularities in the differentiation of the harmonious
+systems might be called forth by single stimuli originating in two
+fixed places in an *independent* way. These would never result in any
+“harmonious,” any proportionate structure, but a structure of the
+“normal” proportionality *and size* at its two ends and non-existent in
+the middle!
+
+So we see there is nothing to be done, either with the means or with the
+formative stimuli; both are entirely unable to account for those kinds
+of localisation during differentiation which appear in our harmonious
+systems.
+
+But is there no possibility of explaining the phenomena of organogenetic
+localisation by any other sort of interaction of parts? Two such
+possibilities may at the first glance seem to exist.
+
+
+*No Explanation Offered by a Chemical Theory of Morphogenesis*
+
+Though never set forth, in the form of a properly worked-out theory,
+the view has sometimes been advocated by biologists, that a chemical
+compound of a very high degree of complication might be the very basis
+of both development and inheritance, and that such a chemical compound
+by its disintegration might direct morphogenesis.
+
+Let us first examine if such a view may hold for the most general
+features of organic morphogenesis. It seems to me that from the very
+beginning there exists one very serious objection to every chemical
+theory of form-building, in the mere fact of the possibility of the
+restoration of form starting from atypical localities. The mere fact,
+indeed, that there is such a thing as the regeneration of a leg of a
+newt--to say nothing about restitution of the harmonious type--simply
+contradicts,[62] it seems to me, the hypothesis, that chemical
+disintegration of one compound may govern the course of morphogenetic
+events: for whence comes the re-existence of the hypothetical compound,
+newly to be disintegrated, after disintegration *has* been completed
+once already? And we even know that regeneration may go on several times
+running from the same locality!
+
+[62] See my article in *Biolog. Centralblatt*, 27, 1907, p. 69. The
+question is rendered still more complicated by the fact that in the case
+of the regeneration, say, of a leg it is not the original “morphogenetic
+compound” which is again required for disintegration, after it has
+become disintegrated once already, but only a specific part of it: just
+that part of it which is necessary for producing the leg! On the other
+hand, it would be impossible to understand, on the basis of physical
+chemistry, how the isolated branchial apparatus of *Clavellina* could
+be transformed, by chemical processes exclusively, into a system of
+which only a certain *part* consists of that substance of which the
+starting-point had been composed in its *completeness*.
+
+But, if we intentionally disregard this difficulty, in spite of
+its fundamental character, how could the hypothesis of chemical
+disintegration give the reason for the differentiation of our
+harmonious-equipotential systems, with special regard to the
+localisation of it; how could it account, in other words, for the
+appearance of typically localised specifications in an organ for which
+no external localising causes can be predicated?
+
+Let us remember that a few original intimate differences exist in our
+harmonious systems: the main directions of the intimate protoplasmic
+structure including polarity and bilaterality. There are therefore
+three times two specified poles in each of these systems, at least in
+bilateral organisms, but no other differences are present in them.
+A few very simple cases of harmonious differentiation might indeed
+be understood on the theory of a disintegrating chemical compound
+in connection with these few differences. Imagine that the original
+compound, of the quantity *a*, is disintegrated to the amount of
+*a*_1; from *a*_1 are formed the two more simple compounds, *b*
+and *c*, both of them in definite quantities; then we have the three
+chemical individuals, *a-a*_1, *b* and *c*, as the constituents of
+our harmonious system; and it now might be assumed, without any serious
+difficulty, though with the introduction of some new hypotheses, that
+the two poles of one of the fundamental axes of symmetry attract *b* and
+*c* respectively, *a-a*_1 remaining unattracted between them. We thus
+should have the three elementary constituents of the system separated
+into three parts, and as they all three are of a definite quantity,
+their separation would mean that the system had been divided into three
+parts, *a-a*_1, *b* and *c*, also with regard to its proper form.
+It is clear, that by taking away any part of the original system, by
+means of operations, there would be taken away a certain amount of the
+original compound; say that *a/n* is left; then, of course, the three
+constituents after the partial disintegration would be *a-a_1/n*,
+*b/n* and *c/n*, and so it follows that the proportionality of
+localisation would really be preserved in any case.
+
+But these considerations, evident as they seem to be in the most
+simple case, fail to satisfy in a really general sense: for two
+different reasons. First, they could never account for the fact that
+the differentiated organism by no means consists of so many different
+compounds as it shows single parts of its differentiation, but that,
+on the contrary, it only consists, as we know, of a certain rather
+limited number of true different morphogenetic elements, these
+elements occurring again and again--as for instance, nervous or
+muscular elements--but typical each time in locality, quantity, and
+form. And in the second place, the very *form* of elementary organs,
+their form as such, does not at all go hand-in-hand with chemical
+differences; this feature alone would absolutely overthrow any sort
+of a chemical morphogenetic theory to account for the problem of
+localisation. Take the typically arranged ring of the mesenchyme
+cells in our Echinus-gastrula, with its two spherical triangles, so
+typically localised; look at any sort of skeleton, in Radiolaria, or in
+starfishes, or in vertebrates: here you have form, real form, but form
+consisting of only one material. Not only is the arrangement of the
+elements of form typical here, *e.g.* the arrangement of the single
+parts of the skeleton of the hand or foot, but also the special form
+of each element is typical, *e.g.* the form of each single bone of the
+foot; and, on a purely chemical theory of morphogenesis the sufficient
+reason for the production of typical form in such a sense would be
+wanting. For atoms or molecules by themselves can only account for form
+which is arranged, so to speak, according to spatial geometry--as in
+fact they do in crystallography; but they can never account for form
+such as the skeleton of the nose, or hand, or foot. You will answer
+me perhaps, that there may be non-chemical agents in the germ,[63]
+responsible for typical form-localisation, but by such reasoning you
+would be departing from a purely chemical theory. Our next paragraph
+will be devoted to this side of the question.
+
+[63] Besides the specified poles determined by the polar-bilateral
+structure of the protoplasm.
+
+That is the principal reason for rejecting all sorts of chemical
+morphogenetic theories put forward to explain the problem of
+localisation; it is more explicit, and therefore, I suppose, still
+more convincing than the more general consideration that the very
+fact of restitutions in itself must contradict the hypothesis that
+a disintegration of compounds might be the directive agency in
+morphogenesis. To sum up: Specificity of organic form does not go
+hand-in-hand with specificity of chemical composition, and therefore
+cannot depend on it; and besides that, specific organic form is such
+that it can never be explained by atomic or molecular arrangement in
+the chemical sense; for, to state it in a short but expressive manner,
+the “form” of an atom or molecule can never be that of a lion or a
+monkey. To assume that would be to go beyond the limits of chemistry in
+chemistry itself.
+
+
+*No Machine Possible Inside the Harmonious Systems*
+
+And now we turn to the last possibility which is left to us in our
+endeavour to “understand” the localisation of the differentiation in our
+harmonious-equipotential systems by the means of physics and chemistry.
+Outside causes have failed to account for it, chemical disintegration
+of a compound has failed too. But could there not exist some sort of
+complicated interactions amongst the parts of the harmonious system
+themselves? Could there not exist some kind of a real machine in the
+system, which, if once set going, would result in the differentiations
+that are to take place? Then we might say that the “prospective
+potency” of the system is in fact that machine; we should know what the
+letter *E* of our equation stood for: viz., a resultant action of many
+complicated elemental interactions, and nothing more.
+
+Weismann, we know already, had assumed that a sort of machine was the
+prime mover of morphogenesis. We have seen that his theory cannot be
+true; the results of experiments most strongly contradict it. But, of
+course, the experiments only showed us that *such* a machine as *he*
+had imagined to exist could not be there, that development could not be
+governed by the disintegration of a given complicated structure into its
+simplest parts. But might not some other machine be imaginable?
+
+We shall understand the word “machine” in a most general sense. A
+machine is a typical configuration of physical and of chemical
+constituents, by the acting of which a typical effect is attained.
+We, in fact, lay much stress upon embracing in our definition of a
+machine the existence of chemical constituents also; we therefore
+understand by the word “machine” a configuration of a much higher
+degree of complication than for instance a steam-engine is. Of course
+a machine, whose acting is to be typical with regard to the three
+dimensions in space, has to be typically constructed with regard to
+these three dimensions itself; a machine that was an arrangement of
+elements in a strict plane could never have typical effects at right
+angles to that plane. This is a point which must well be kept in mind
+in all hypothetical considerations about machines that claim to explain
+morphogenesis.
+
+It must be granted that a machine, as we understand the word, might very
+well be the motive force of organogenesis in general, if only normal,
+that is to say, if only undisturbed development existed, and if a taking
+away of parts of our systems led to fragmental development.
+
+But we know that, at least in our harmonious-equipotential systems,
+quite another process occurs after parts have been taken away: the
+development that occurs is not fragmental but whole, only on a smaller
+scale.
+
+And we know, further, that this truly whole development sets in
+irrespective of the amount and direction of the separation. Let us first
+consider the second of these points. There may be a whole development
+out of each portion of the system--above certain limits--which is, say,
+of the volume *V*. Good! Then there ought to exist a machine, like
+that which exists in the whole undisturbed system, in this portion *V*
+also, only of smaller dimensions; but it also ought to exist in the
+portion *V*_1 which is equal to *V* in amount, and also in *V*_2, in
+*V*_3, *V*_4 and so on. Indeed, there do exist almost indefinitely
+many *V*_n all of which can perform the whole morphogenesis, and all
+of which therefore ought to possess the machine. But these different
+portions *V*_n are only partly different from each other in spatial
+relation. Many parts of *V*_2 are also parts of *V*_1 and of *V*_3
+and of *V*_4 and so on; that is to say, the different volumes *V*_n
+overlap each other successively and in such a manner that each following
+one exceeds the preceding one in the line by a very small amount only.
+But what then about our machines? Every volume which may perform
+morphogenesis completely must possess the machine in its totality. As
+now every element of one volume may play any possible elemental rôle in
+every other, it follows that each part of the whole harmonious system
+possesses any possible elemental part of the machine equally well, all
+parts of the system at the same time being constituents of different
+machines.
+
+A very strange sort of machine indeed, which is the same in all its
+parts (Fig. 14)!
+
+[Illustration: Fig. 14.--An “Harmonious-equipotential System” of
+whatever kind.
+
+According to the “machine-theory” of life this system ought to possess
+a certain unknown very complicated machine *in its completeness*:
+
+ (*a*) in its total length,
+ and (*b*) in each of the equal volumes *v*, *v*_1, *v*_2, *v*_3 and
+ so on,
+ and (*c*) in each of the unequal volumes *w*, *x*, *y*, and so on,
+ and (*d*) in every imaginable volume, no matter of what size.
+
+Therefore the “machine-theory” of life is absurd.]
+
+But we have forgotten, I see, that in our operation the absolute amount
+of substance taken away from the system was also left to our choice.
+From this feature it follows that not only all the different *V*_n,
+all of the same size, must possess the hypothetic machine in its
+completeness, but that all amounts of the values *V*_n-*n*, *n* being
+variable, must possess the totality of the machine also: and all values
+*V*_n-*n*, with their variable *n*, may again overlap each other.
+
+Here we are led to real absurdities!
+
+But what is the conclusion of our rather wild considerations?
+
+It seems to me that there is only one conclusion possible. If we
+are going to explain what happens in our harmonious-equipotential
+systems by the aid of causality based upon the constellation of single
+physical or chemical factors and events, there *must* be some such
+thing as a machine. Now the assumption of the existence of a machine
+proves to be absolutely absurd in the light of the experimental facts.
+*Therefore there can be neither any sort of a machine nor any sort of
+causality based upon constellation underlying the differentiation of
+harmonious-equipotential systems.*
+
+For a machine, typical with regard to the three chief dimensions
+of space, cannot remain itself if you remove parts of it or if you
+rearrange[64] its parts at will.
+
+[64] The pressure experiments and the dislocation experiments come into
+account here; for the sake of simplicity they have not been alluded to
+in the main line of our argument.
+
+Here we see that our long and careful study of morphogenesis has been
+worth while: it has afforded us a result of the very first importance.
+
+
+*The Autonomy of Morphogenesis Proved*
+
+No kind of causality based upon the constellations of single physical
+and chemical acts can account for organic individual development; this
+development is not to be explained by any hypothesis about configuration
+of physical and chemical agents. Therefore there must be something
+else which is to be regarded as the sufficient reason of individual
+form-production. We now have got the answer to our question, what
+our constant *E* consists in. It is not the resulting action of a
+constellation. It is not only a short expression for a more complicated
+state of affairs, it expresses *a true element of nature*. Life, at
+least morphogenesis, is not a specialised arrangement of inorganic
+events; biology, therefore, is not applied physics and chemistry: life
+is something apart, and biology is an independent science.
+
+All our results at present, indeed, are negative in their form; our
+evidence was throughout what is called *per exclusionem*, or indirect
+or apagogic. There were excluded from a certain number of possibilities
+all except one; a disjunctive proposition was stated in the form: *E*
+is either this, or that, or the other, and it was shown that it could
+not be any of all these except one, therefore it was proved to be that
+one. Indeed, I do not see how natural science could argue otherwise;
+no science dealing with inorganic phenomena does; something new and
+elemental must always be introduced whenever what is known of other
+elemental facts is proved to be unable to explain the facts in a new
+field of investigation.
+
+We shall not hesitate to call by its proper name what we believe we have
+proved about morphogenetic phenomena. What we have proved to be true
+has always been called *vitalism*, and so it may be called in our days
+again. But if you think a new and less ambitious term to be better for
+it, let us style it the doctrine of the *autonomy of life*, as proved
+at least in the field of morphogenesis. I know very well that the word
+“autonomy” usually means the faculty of *giving* laws to oneself, and
+that in this sense it is applied with regard to a community of men;
+but in our phrase autonomy is to signify the *being subjected* to laws
+peculiar to the phenomena in question. This meaning is etymologically
+defensible, and besides that I perhaps may remind you of a certain
+chapter of Professor Ward’s Gifford Lectures, in which he holds the view
+that, psychologically and epistemologically, there is more than a mere
+verbal relation between the civil and the natural “law.”
+
+Vitalism then, or the autonomy of life, has been proved by us
+indirectly, and cannot be proved otherwise so long as we follow the
+lines of ordinary scientific reasoning. There can indeed be a sort of
+direct proof of vitalism, but now is not the time to develop this proof,
+for it is not of the purely scientific character, not so naïve as our
+present arguments are, if you choose to say so. An important part of our
+lectures next summer will be devoted to this direct proof.
+
+
+“*Entelechy*”
+
+But shall we not give a name to our vitalistic or autonomous factor
+*E*, concerned in morphogenesis? Indeed we will, and it was not without
+design that we chose the letter *E* to represent it provisionally. The
+great father of systematic philosophy, Aristotle, as many of you will
+know, is also to be regarded as the founder of theoretical biology.
+Moreover, he is the first vitalist in history, for his theoretical
+biology is throughout vitalism; and a very conscious vitalism indeed,
+for it grew up in permanent opposition to the dogmatic mechanism
+maintained by the school of Democritus.
+
+Let us then borrow our terminology from Aristotle, and let that factor
+in life phenomena which we have shown to be a factor of true autonomy be
+called *Entelechy*, though without identifying our doctrine with what
+Aristotle meant by the word έντελέχεια. We shall use this word only as a
+sign of our admiration for his great genius; his word is to be a mould
+which we have filled and shall fill with new contents. The etymology of
+the word ἐντελέχεια allows us such liberties, for indeed we have shown
+that there is at work a something in life phenomena “which bears the end
+in itself,” ὃ ἔχει ἐν ἑαυτᾣ τὸ τέλος.
+
+Our concept of entelechy marks the end of our analysis of individual
+morphogenesis. Morphogenesis, we have learned, is “epigenesis” not only
+in the descriptive but also in the theoretical sense: manifoldness
+in space is produced where no manifoldness was, real “evolutio” is
+limited to rather insignificant topics. But was there nothing “manifold”
+previous to morphogenesis? Nothing certainly of an *extensive*
+character, but there was something else: there was entelechy, and thus
+we may provisionally call entelechy an “*intensive manifoldness*.”
+That then is our result: not evolutio, but epigenesis--“epigenesis
+vitalistica.”
+
+
+*Some General Remarks on Vitalism*
+
+We now shall leave entelechy where it stands: next summer we shall turn
+back to it and shall make its full logical and ontological analysis
+our chief study. At present we are satisfied with having proved its
+existence in nature, with having laid some of the foundations of a
+doctrine to be based upon it. I hope that these foundations will evince
+themselves strong: that is all-important.[65] It indeed has been the
+fault of all vitalism in the past that it rested on weak foundations.
+Therefore the discussion of the basis underlying our doctrine of the
+autonomy of life is to occupy us still a considerable time. We shall
+devote to it two more of this year’s lectures and three of the next; we
+shall examine all sorts of phenomena of life in order to find out if
+there are any further proofs of vitalism, independent perhaps, of what
+we way call our *first proof*, which is based upon the analysis of the
+*differentiation of harmonious-equipotential systems*. We shall find
+some more independent proofs; and besides that we shall find many kinds
+of phenomena upon which future times perhaps may erect more of such
+independent proofs.
+
+[65] My “first proof of vitalism” was first developed in the paper, “Die
+Localisation morphogenetischer Vorgänge,” Leipzig, 1899. (See additional
+remarks in *Organische Regulationem*, Leipzig, 1901, and in *Archiv
+für Entwickelungsmechanik*, 14, 1902.) I cannot admit that any really
+serious objection has been brought forward against it. (See my articles
+in *Biologisches Centralblatt*, 22, 23, 27, and in *Ergebnisse d. Anat.
+u. Entwickelungsgesch*. 11, 14.) An historical sketch of vitalism will
+be found in my book, *Der Vitalismus als Geschichte und als Lehre*,
+Leipzig, 1905.
+
+For we shall be chary of bestowing the name “proof” except on what is a
+proof indeed, of course according to our critical conviction. Vitalistic
+views in biology have arisen in rather numerous forms during the last
+fifteen years, especially in Germany--though in very strong contrast to
+the so-called official German biology--but I can only admit that one of
+all the arguments of “neo-vitalism” has proved its statements. I refer
+to the theory of “morphaesthesia” as developed by Noll, which we shall
+study briefly in the next lecture. I cannot concede that Reinke or
+Schneider or Pauly have really proved what they believe, and I cannot
+even allow to the most original thinker in this field, Gustav Wolff,
+that he has given a real demonstration of his views. He states that the
+existence of so-called “primary purposefulness,” that is, the existence
+of adaptive processes, which cannot be imagined to have arisen on
+Darwinian principles, is able to prove vitalism; but I say that it only
+proves teleology, which is a broader concept than vitalism.
+
+The possibility of a machine at the root of the phenomena in question
+always has to be excluded in order that vitalism may be proved, and I
+cannot grant that the necessity of such an exclusion has been actually
+shown by any of my fellow-combatants against so-called mechanism, except
+Noll.[66]
+
+[66] We are dealing here with morphogenesis and so-called vegetative
+physiology only; to certain psychologists, who have refuted the theory
+of psycho-physical parallelism, I must grant that they also have proved
+vitalism. (See Volume II.)
+
+
+*The Logic of our First Proof of Vitalism*
+
+Let us devote the end of our present lecture to an account of the
+logical means by which it has been possible to develop what we hope will
+be regarded as a true *proof* of life autonomy.
+
+Firstly, we have looked upon the phenomena of morphogenesis without
+any prepossessions; we may say that we have fully surrendered ourselves
+to them; we have not attacked them with any sort of dogmatism except
+the inherent dogmatism of all reasoning. But this dogmatism, if it may
+be called so, does not postulate that the results of the inorganic
+doctrines must hold for the organic world, but only that both the
+inorganic and the organic must be subject to certain most general
+principles.
+
+By studying life as a given phenomenon, by fully devoting ourselves to
+our problem, we not only have analysed into its last elements what was
+given to us as our subject, but we also, more actively, have created new
+combinations out of those elements: and it was from the discussion of
+these positive constructions that our argument for vitalism was derived.
+
+We have analysed morphogenesis into elementary processes, means,
+potency, formative stimulus, just as the physicist analyses mechanics
+into time, velocity, mass, and force; we have then rearranged
+our elements into “systems”--the equipotential systems, the
+harmonious-equipotential system in particular, just as the physicist
+composes his elements into the concepts of momentum or of kinetic energy
+or of work. And finally, we have discussed our compositions and have
+obtained our result, just as the physicist gets his ultimate results by
+discussing work and kinetic energy and momentum.
+
+Of course the comparison is by no means intended to show that mechanics
+and biology are sciences of the same kind. In my opinion, they are not
+so at all; but nevertheless there do exist similarities of a logical
+kind between them.
+
+And it is not the formal, logical character alone which allows us to
+compare biology with other natural sciences: there is still something
+more, there is one kind of assumption or postulate, or whatever you
+may choose to call it, without which all science whatever would be
+altogether *impossible*. I refer to the concept of *universality*. All
+concepts about nature which are gained by positive construction out of
+elements resulting from analysis, claim to be of *universal validity*;
+without that claim there could indeed be no science.
+
+Of course this is no place for a lecture on methodology, and it
+therefore must suffice to make one remark with special regard to
+our purpose, which we should like to emphasise. Our concept of the
+harmonious-equipotential system--say rather, our concept of the
+prospective potency itself--presumes the understanding that indeed *all*
+blastomeres and *all* stems of *Tubularia*, including those upon which
+we have *not* carried out our experiments, will behave like those we
+have experimented with; and those concepts also presume that a certain
+germ of Echinus, *A*, the blastomeres of which were not separated,
+would have given two whole larvae, if separation had taken place, while
+another germ, *B*, which actually gave us two larvae after separation,
+would only have given one without it. Without this presumption the
+concept of “potency” is meaningless, and, indeed, every assumption of a
+“faculty” or a “possibility” would be meaningless in the whole area of
+science.
+
+But this presumption can never be proved; it can only be postulated. It
+therefore is only with this postulate that our first proof of vitalism
+holds; but this restriction applies to *every* law of nature.
+
+I cannot force you to agree with this postulate: but if you decline
+you are practically saying that there exists a sort of pre-established
+harmony between the scientific object and the scientist, the scientist
+always getting into his hands such objects only as have been
+predestinated from the very beginning to develop two larvae instead of
+one, and so on.
+
+Of course, if that is so, no proof of natural laws is possible at all;
+but nature under such views would seem to be really dæmonic.
+
+And so, I hope, you will grant me the postulate of the universality
+of scientific concepts--the only “hypothesis” which we need for our
+argument.
+
+
+4. ON CERTAIN OTHER FEATURES OF MORPHOGENESIS ADVOCATING ITS AUTONOMY
+
+Our next studies on the physiology of form will be devoted in the first
+place to some additional remarks about our harmonious-equipotential
+systems themselves, and about some other kinds of morphogenetic
+“systems” which show a certain sort of relationship with them. For it is
+of the greatest importance that we should become as familiar as possible
+with all those facts in the physiology of form upon the analysis of
+which are to be based almost all of the future theories that we shall
+have to develop in biology proper and philosophical. Our discussions, so
+far as they relate to questions of actual fact, will contain only one
+other topic of the same importance.
+
+But though it is designed to complete and to deepen our analysis,
+the present considerations may yet be said to mark a point of rest
+in the whole of our discussions: we have followed one single line of
+argumentation from the beginning until now; this line or this stream of
+thought, as you might call it, is now to break into different branches
+for a while, as if it had entered from a rocky defile into a plain.
+It seems to me that such a short rest will be not unconducive to a
+right understanding of all we have made out; and such a full and real
+conceiving again, such a realising of our problems of morphogenesis and
+their solutions, will be the best preparation for the philosophical part
+of these lectures.
+
+
+HARMONIOUS-EQUIPOTENTIAL SYSTEMS FORMED BY WANDERING CELLS
+
+All of the harmonious-equipotential systems which we have studied so
+far were the bases of histological differentiation; that is to say, the
+processes of their differentiation consisted in specifically localised
+elements of theirs becoming different *in situ*. Now we know at least
+one type of systems which also may be called harmonious-equipotential,
+but the differentiation of which does not simply relate to elements at
+a fixed place. An additional phenomenon enters here into the sphere of
+the others. The elements not only become different where they are, but
+a specific changing of locality, a specific kind of wandering, goes
+hand-in-hand with differences relating to the prospective value to be
+attained. I am speaking of the formation of the larval skeleton of
+our well-known Echinus. We know that the mesenchyme cells, which have
+left the blastoderm and are arranged in a sort of ring of bilateral
+structure, are the starting-point of this skeleton: it indeed originates
+in a sort of secretive process on the part of the cells; the cells
+are moving about and are secreting carbonate of lime during their
+wandering. The experiments now have shown, as we know, that a whole,
+though smaller, skeleton may also be formed, if only a half or a quarter
+of the mesenchyme cells are present, as happens to be the case in all
+experiments with isolated blastomeres of the two or four-cell stage of
+cleavage. It is clear that in these cases the performance of each single
+cell must be different from what it is in the normal case, and that
+the same sort of differences in the morphogenetic performances appears
+again, if the two- and the four-cell stage are compared with each other.
+And there are still some other phenomena showing the possibility of
+different performances being carried out by the individual cells. Peter
+has shown that the number of mesenchyme cells may vary enormously under
+certain conditions; but, in spite of that, the skeleton always will
+be complete. It may be said that this line of research is only of a
+relative value to our own questions, as, of course, variability relates
+to different individuals: but it seems to me that it adds a very good
+supplementary instance to what the experiment on the individual itself
+has established.
+
+We should only be repeating ourselves if we were to analyse again what
+happens here as the expression of the harmonious-equipotentiality
+itself. But indeed there occurs something new in this instance: the
+single mesenchyme cell not only has to perform in each case that single
+act of specific secretion which the case requires, but it also has to
+wander to the right place in order to perform it; there must be some
+order, not only about the acts of secretion after wandering, but also in
+the migrations themselves. If undisturbed ontogeny alone were possible,
+and if therefore a theory like that of Weismann were in place, we might
+say perhaps that each mesenchyme-cell is specified not only as to its
+performance in secretion, but also with regard to its chemotactical
+irritability, the latter being typically localised, so that its effect
+becomes typical, thanks to the typical arrangement of all the cells
+with respect to each other. But that is certainly not the case. Now, you
+may ask yourselves if you could imagine any sort of a machine, which
+consists of many parts, but not even of an absolutely fixed number, all
+of which are equal in their faculties, but all of which in each single
+case, in spite of their potential equality, not only produce together
+a certain typical totality, but also arrange themselves typically in
+*order* to produce this totality. We *are* indeed familiar with certain
+occurrences in nature where such curious facts are observed, but I doubt
+if you would speak of “machines” in these cases. The mesenchyme-cells,
+in fact, behave just as a number of workmen would do who are to
+construct, say, a bridge. All of them *can* do every single act, all of
+them also *can* assume every single position: the result always is to
+be a perfect bridge; and it is to be a perfect bridge even if some of
+the workmen become sick or are killed by an accident. The “prospective
+values” of the single workman change in such a case.
+
+I well know that it is only an analogy which I am offering to you.
+The mesenchyme-cells have not “learned,” have no “experience.” All
+that is to occupy us next summer. But in spite of it, there is truth
+in the analogy; and perhaps you will prefer it to the merely abstract
+consideration.
+
+
+ON CERTAIN COMBINED TYPES OF MORPHOGENETIC SYSTEMS
+
+For the sake of completeness it may be remarked, only by the way, that
+the type of the proper harmonious-equipotential system may go hand in
+hand with another type of “systems” which play a part in morphogenesis;
+a type which we have shortly mentioned already and which will be studied
+fully a few chapters later. We know that there are equipotential systems
+with complex potencies: that is to say, systems which may produce a
+whole organism equally well from any one of their elements; we know the
+cambium of Phanerogams to be such a system. Now it is easily understood
+that the germ of our Echinus, say in the stage of two or four or eight
+cleavage cells, is not only an harmonious-equipotential system, but
+a complex-equipotential system too. Not only may there arise a whole
+organism out of 2/4 or 3/4 or 3/8, 4/8, 5/8, 6/8, 7/8 of its elements,
+in which cases the harmonious rôle of the single element with regard to
+its single performance in a totality is variable, but there may also
+arise four whole single larvae out of the four cells of the four-cell
+stage, or eight single whole larvae out of the eight-cell stage.[67]
+In these cases, of course, each of the four or eight elements has
+performed not a part of the totality, changing with its “position,” but
+the totality itself. With respect to these possible performances the
+“systems” present in the four or eight-cell stages of cleavage must be
+called complex-equipotential ones.
+
+[67] The eight larvae would be incomplete in some respect, but not with
+regard to symmetry. They would be “whole” ones, only showing certain
+defects in their organisation. See page 65 note 1, and page 73.
+
+We propose to give the name of *mixed-equipotential systems* to all
+those equipotential systems which, at the same time, may be regarded
+as belonging to the harmonious or to the complex type. It is not only
+among cleavage-stages that they are to be found; you may also find them
+very clearly exhibited in our ascidian *Clavellina* for instance. We
+know already that the branchial apparatus of this form is typically
+harmonious-equipotential, but it is complex-equipotential too, for it
+also may regenerate what is wanting in the proper way, by a budding
+from the wound; and the same is true of many other cases, the flatworm
+*Planaria* for instance.
+
+Another type of systems, which might be said to be of a higher degree,
+is exhibited in some very strange phenomena of regeneration. It was
+first shown most clearly by some experiments of Godlewski’s that a
+whole tail may be regenerated from a wound inflicted on the body of
+a newt, even if this wound involves section of only a portion of the
+body-diameter. Section of the whole of the body-diameter of course
+would cause the formation of the whole tail also; but it was found that
+even an incomplete cross-section of the body is capable of performing
+the whole on a smaller scale. The series of possible cross-sections
+which are all capable of regeneration would have to be called a
+system of the complex type in this case; but, now we learn that every
+*single* cross-section is of the harmonious type, we must speak of
+*complex-harmonious systems*. What we have described is not the only
+instance of our new type of morphogenetic systems. Some other instances
+had been discovered a few years earlier, though nobody had pointed
+out their true significance. In the flatworm *Planaria* a partial
+cross-section is also capable of forming a whole structure, say a head,
+and all cases of so-called “super-regeneration” after the infliction of
+a complicated wound probably belong here also.
+
+You may say that our two additions to the theory of systems are merely
+formal, and indeed I am prepared to concede that we shall not learn
+anything altogether new from their discussion: their analysis would lead
+either to what was our “first proof” of the autonomy of life-phenomena
+or to what will be our “second” one. But the mere descriptions of the
+facts discovered here will interest you, I think, and will fill your
+minds with more vivid pictures of the various aspects of form-autonomy.
+
+While dealing with our harmonious-equipotential systems as the
+starting-points of processes of restitution, *e.g.* in *Tubularia*,
+*Clavellina*, the flatworms, and other instances, we always have
+regarded cross-sections of the body as constituting the elements of
+equipotentiality. Now cross-sections, of course, are by no means simple
+in themselves, but are made up of very different tissues, which are
+derivates of all three of the original germ layers--ectoderm, mesoderm,
+and endoderm. Owing to this composite character of the cross-sections,
+taken as elements of harmonious systems, a special phenomenon of
+morphogenesis is presented to us, which teaches somewhat more than the
+mere concept of harmonious-equipotentiality can express. If composite
+elements concerned in morphogenesis result in one whole organisation
+in spite of the development of the single tissues of these elements
+going on independently, then there must be a sort of correspondence
+or reciprocity of the harmonious development among these tissue
+constituents themselves; otherwise a proportionate form could not be the
+final result. We may conveniently speak of a *reciprocity of harmony* as
+existing between the single tissues or germ layers which constitute many
+harmonious-equipotential systems, and there can be little doubt that we
+have here an important feature with regard to general morphogenesis.[68]
+
+[68] Reciprocal harmony may be reduced in some cases to the given
+proportions of one original harmonious system, from which the single
+constituents of the complicated system, showing reciprocal harmony, are
+derived. Then we have only an instance of “harmony of constellation”
+(see p. 109). But reciprocal harmony seems to become a problem itself,
+if it occurs in restitutions starting from quite a typical point,
+selected by the experimenter. It will be a problem of future research
+to give an exact formula of what happens here. Reciprocal harmony also
+occurs in regeneration proper. It is known that the formation of the
+regenerative bud and the differentiation of this bud follow each other.
+As the bud is composed of different elementary systems, it follows that
+these different systems, of which every single one is harmonious, also
+have to work in reciprocity to each other, in order that one whole
+proportionate formation may result.
+
+A few other groups of morphogenetic facts may find their proper place
+here, though they are not properly to be regarded as additions to the
+theory of harmonious systems but as forming a sort of appendix to it.
+
+
+THE “MORPHAESTHESIA” OF NOLL[69]
+
+[69] *Biol. Centralblatt.* 23, 1903.
+
+We may briefly mention that group of botanical phenomena, by which
+the botanist Noll has been led to the concept of what he calls
+“morphaesthesia,” or the “feeling” for form; a concept, the full
+discussion of which would lead to almost the same conclusions as our
+analysis of the harmonious systems has done. In the Siphoneae, a
+well-known order of marine algae with a very complicated organisation
+as to their exterior form, the protoplasm which contains the nuclei is
+in a constant state of circulation round the whole body, the latter
+not being divided by proper cell-walls. On account of this constant
+movement it is certainly impossible to refer morphogenetic localisation
+to definite performances of the nuclei. Nor can any sort of structure
+in the outer protoplasmic layer, which is fixed, be responsible for
+it, for there is no such structure there: hence there must be a sort
+of feeling on the part of the plant for its relative body localities,
+and on account of this feeling morphogenesis occurs. This “feeling” is
+styled “morphaesthesia” by Noll, and to it he tries to refer all sorts
+of different botanical form-phenomena,[70] for instance what is called
+“autotropism,” that is, the fact that branches of plants always try to
+reassume their proper angle with regard to their orientation on the main
+axis, if this orientation has been disturbed. It may be an open question
+if this particular application of the theory is right: certainly
+there seems to be much truth in the establishment of the concept of
+morphaesthesia, and we only have to object to its psychological name.
+But that may be done in a more general form on a later occasion.
+
+[70] Certain phenomena of the physiology of growth of *Geranium
+Robertianum*, recently discussed by Francé from a vitalistic point of
+view (*Zeitschr. Entw. lehre*. 1, 1907, Heft iv.), might also belong
+here. I cannot see an independent proof of vitalism in these facts if
+taken by themselves; a pre-existing “machine” cannot be absolutely
+excluded here.
+
+
+RESTITUTIONS OF THE SECOND ORDER
+
+In the hydroid polyp *Tubularia*, already familiar to us as being a most
+typical representative of the harmonious-equipotential systems, a very
+interesting phenomenon has been discovered[71], almost unparalleled at
+present but nevertheless of a general importance, a phenomenon that
+we may call a restitution of a restitution, or a restitution of the
+second order. You know that the first appearance of the new head of
+*Tubularia*, after an operation, consists in the formation of two rings
+of red lines, inside the stem, these rings being the primordia of the
+new tentacles. I removed the terminal ring by a second operation soon
+after it had arisen, disturbing in this way the process of restitution
+itself: and then the process of restitution itself became regulated. The
+organism indeed changed its course of morphogenesis, which was serving
+the purposes of a restitution, in order to attain its purpose in spite
+of the new disturbance which had occurred. For instance, it sometimes
+formed two rings out of the one that was left to it, or it behaved
+in a different way. As this difference of morphogenetic procedure is
+a problem by itself, to be discussed farther on, we shall postpone a
+fuller description of this case of a restitution of the second degree.
+
+[71] Driesch, *Arch. Entw. Mech.* 5, 1897.
+
+At present I do not see any way of proving independently the autonomy of
+life by a discussion of these phenomena; their analysis, I think, would
+again lead us to our problem of localisation and to nothing else; at
+least in such an exact form of reasoning as we demand.
+
+
+ON THE “EQUIFINALITY” OF RESTITUTIONS[72]
+
+[72] Driesch, *Arch. Entw. Mech.* 14, 1902.
+
+I have told you already that *Tubularia* in the phenomena of the
+regulation of restitutions offers us a second problem of a great general
+importance, the problem of the *Equifinality of Restitutions*. There
+indeed may occur restitutions, starting from one and the same initial
+state and leading to one and the same end, but using very different
+means, following very different ways in the different individuals of one
+and the same species, taken from the same locality, or even colony.
+
+Imagine that you have a piece of paper before you and wish to sketch
+a landscape. After drawing for some time you notice that you have
+miscalculated the scale with regard to the size of the paper, and
+that it will not be possible to bring upon the paper the whole of the
+landscape you want. What then can you do? You either may finish what you
+have begun to draw, and may afterwards carefully join a new piece of
+paper to the original one and use that for the rest of the drawing; or
+you may rub out all you have drawn and begin drawing to a new scale; or
+lastly, instead of continuing as you began, or erasing altogether, you
+may compromise as best you can by drawing here, and erasing there, and
+so you may complete the sketch by changing a little, according to your
+fancy, the proportions as they exist in nature.
+
+This is precisely analogous to the behaviour of our *Tubularia*.
+*Tubularia* also may behave in three different ways, if, as I described
+to you, the terminal one of its two newly arisen rings of tentacle
+primordia is removed again. It may complete what is left, say the basal
+tentacle ring, then put forth from the horny skeleton (the “perisarc”)
+the new head as far as it is ready, and finally complete this head
+by a regular process of budding regeneration. But it also may behave
+differently. It may “erase” by a process of retro-differentiation all
+that has been left of what had already been formed, and then may form
+*de novo* the totality of the primordia of a new head. Or, lastly, it
+may remove a part of the middle of the one ring of tentacle rudiments
+which was left, and may use this one ring for the formation of two,
+which, of course, will not be quite in the normal relations of place
+with regard to each other and to the whole, but will be regulated
+afterwards by processes of growth. Thus, indeed, there is a sort of
+equifinality of restitution: one starting-point, one end, but three
+different means and ways.
+
+It would, of course, contradict the principle of univocality, as we
+shall see more fully later on, to assume that there actually are
+different ways of regulation whilst all the conditions and stimuli are
+the same. We are obliged to assume, on the contrary, that this is not
+the case, that there are certain differences in the constellation, say
+of the general conditions of age or of metabolism, which are responsible
+for any given individual choosing one process of restitution instead
+of another; but even then the phenomenon of equifinality remains very
+striking.
+
+It has long been known that restitution in general does not always
+follow the same lines of morphogenesis as are taken by ontogeny, and it
+was this feature that once led Roux to point out that the adult forms
+of organisms seem to be more constant than their modes of origin. But,
+comparing ontogeny with restitution in general, we see that only the
+ends are the same, not the points of starting; the latter are normal or
+non-typical in ontogeny, atypical in restitution. In the new discoveries
+of an equifinality of restitutions we have the *same* starting-point,
+which is decidedly non-typical but atypical, *i.e.* dependent on our
+arbitrary choice, leading by *different* ways always to the *same* end.
+
+There may be many who will regard the fact of equifinality as a proof of
+vitalism. I should not like to argue in this easy way; I indeed prefer
+to include part of the phenomena of equifinality in our first proof of
+autonomy, and part in the second one, which is to follow.
+
+Another important phenomenon of the equifinality of regulation was
+discovered by Morgan. A species of the flatworm *Planaria* was found to
+restore its totality out of small pieces either by regeneration proper,
+if the pieces were fed, or by a sort of rearrangement of material,
+on the basis of its harmonious-equipotentiality, if they were kept
+fasting. It is important to note that here we see one of the conditions
+determining the choice of the way to restoration, as we also do in the
+well-known equifinal restitutions of the root in plants, where the
+behaviour of the organism depends on the distance of the operation-wound
+from the tip.[73] In *Tubularia* the actual stage of restitution that
+has been already reached by the stem when the second operation takes
+place, may account for the specification of its future organogenesis,
+but this is not at all clearly ascertained at present.
+
+[73] The root may be restored by regeneration proper, or by the
+production of adventitious roots, or by one of the side-roots changing
+its geotropism from horizontal to positive, according to the smaller or
+greater distance of the wound from the tip.
+
+*Clavellina* also shows equifinality in its restitution, as has already
+been shortly mentioned. The isolated branchial apparatus may restitute
+itself by retro-differentiation to an indifferent stage followed by
+renovation; or it may regenerate the intestine-sac in the proper way.
+Nothing is known here about the conditions, except perhaps that young
+individuals seem more apt to follow the first of these two ways, older
+ones the second; but there are exceptions to this rule.
+
+The discussion of other instances of equifinality, though important in
+themselves, would not disclose anything fundamentally new, and so we may
+close the subject with the remark that nothing can show better than the
+fact of the equifinality of restitutions how absolutely inadequate all
+our scientific conceptions are when confronted with the actual phenomena
+of life itself. By analysis we have found differences of potencies,
+according as they are simple or complex; by analysis we have found
+differences of “systems,” differences of means, and indeed we were glad
+to be able to formulate these differences as strictly as possible: but
+now we see how, in defiance of our discriminations, one and the same
+species of animals behaves now like one sort of our “systems,” and now
+like the other; how it uses now one sort of “potencies,” now another.
+
+But even if it is granted that, in the presence of such phenomena of
+life, our endeavour seems to be like a child’s play on the shores of the
+ocean, I do not see any other way for us to go, so long, at least, as
+our goal is human science--that is, a study of facts as demanded by our
+mental organisation.
+
+
+REMARKS ON “RETRO-DIFFERENTIATION”
+
+We shall finish this part of our studies by mentioning a little more
+explicitly one fundamental fact which has already entered incidentally
+into our considerations, viz. *retro-* or *back-differentiation*.[74]
+We know that it occurs in *Clavellina* and in *Tubularia*; we may add
+that it also happens in *Hydra*, and that in the flatworm *Planaria*
+the pharynx, if it is too large for a piece that is cut out, may be
+differentiated back and be replaced by a new pharynx, which is smaller.
+
+[74] “Retro”-differentiation, of course, is not “Re”-differentiation
+(“Umdifferenzierung,” see p. 111), though it may help it to occur.
+
+It is not death and sloughing of parts that occurs in these cases,[75]
+but a real process of active morphogenesis; not, however, a process
+consisting in the production of visible manifoldness, but the opposite.
+Loeb was the first to lay much stress upon this topic, and indeed, there
+may appear a very strange problem in its wake: the problem, whether
+*all* morphogenesis might be capable perhaps of going backwards under
+certain conditions.
+
+[75] Of course such a real decay of parts may happen in other cases.
+
+It is important to note that in most[76] cases retro-differentiation
+occurs in the service of restitution: it goes on wherever restitution
+requires it. This fact alone would show that not very much could be
+explained here by the discovery of modern chemistry, important as
+it is, that one and the same “ferment” or “enzyme” may affect both
+the composition and the decomposition of the same compound. We could
+regard what is called “catalysis” solely as an agent in the service of
+entelechy. But this point also will become clearer in another part of
+the work.
+
+[76] Certain cases of retro-differentiation occurring under conditions
+of strict fasting will be described in a later chapter.
+
+
+
+
+*C.* ADAPTATION
+
+INTRODUCTORY REMARKS ON REGULATIONS IN GENERAL
+
+
+We have finished our long account of individual morphogenesis proper.
+If we look back upon the way we have traversed, and upon those topics
+in particular which have yielded us the most important general results,
+the material for the higher analysis which is to follow, it must
+strike us, I think, that all these results relate to regulations.
+In fact, it is “secondary” form-regulations, according to our
+terminology, that we have been studying under the names of equifinality,
+back-differentiation, restitution of the second order, and so on, and
+our harmonious-equipotential systems have figured most largely in
+processes of secondary form-regulations also. But even where that has
+not been the case, as in the analysis of the potencies of the germ in
+development proper, form-regulations of the other type have been our
+subject, regulations of the primary or immanent kind, the connection
+of normal morphogenetic events being regulatory in itself. It was not
+the phenomenon of organic regulation as such that afforded us the
+possibility of establishing our proof of the autonomy of morphogenesis:
+that possibility was afforded us by the analysis of the distribution of
+potencies; but upon this distribution regulation is based, and thus
+we may be said to have studied some types of regulation more or less
+indirectly when analysing potencies.
+
+It therefore seems to me that we shall have hopes of a successful issue
+to our inquiries, if we now, on passing to what is called the physiology
+of the vegetative functions, proceed to focus our attention on the
+concept of regulation as such. And that is what we shall do: on our
+way through the whole field of physiology, we shall always stop at any
+occurrence that has any sort of regulatory aspect, and shall always ask
+ourselves what this feature has to teach us.
+
+But let us first try to give a proper definition of our concept. We
+shall understand by “regulation” any occurrence or group of occurrences
+on a living organism which takes place after any disturbance of
+its organisation or normal functional state, and which leads to a
+reappearance of this organisation or this state, or at least to a
+certain approach thereto. Organisation is disturbed by any actual
+removal of parts; the functional state may be altered by any change
+among the parts of the organism on the one hand, by any change of the
+conditions of the medium on the other; for physiological functioning
+is in permanent interaction with the medium. It is a consequence of
+what we have said that any removal of parts also changes the functional
+state of the organism, but nevertheless organisation is more than a mere
+sum of reactions in functional life. All regulations of disturbances
+of organisation may be called *restitutions*, while to regulations of
+functional disturbances we shall apply the name *adaptations*. It is
+with *adaptations* that we have to deal in the following.
+
+Let us begin our studies of adaptations in a field which may justly
+be called a connecting link between morphogenesis and physiology
+proper, not yet wholly separated from the science of the organic form,
+morphology.
+
+
+1. MORPHOLOGICAL ADAPTATION
+
+*Morphological adaptation* is a well-established fact, and I need only
+mention the striking differences between the land and water form of
+amphibious plants, or the differences between the same species of plants
+in the Alps and in the plains, or the very different aspect of the arms
+of an athlete and of an ascetic, to recall to your memory what is meant
+by this term.
+
+Morphological adaptation is no part of individual morphogenesis proper,
+but occurs at the end of it; at least it never occurs previous to the
+full individual life of an organism, previous to its true functional
+life; for it relates to the functions of the complete organism.
+
+
+THE LIMITS OF THE CONCEPT OF ADAPTATION
+
+It is especially, though by no means exclusively, among plants that
+morphological adaptation assumes its most marked forms; and this topic,
+indeed, may very easily be understood if we remember that plant-life
+is in the very closest permanent dependence on the medium, and that
+this medium is liable to many changes and variations of all kinds.
+In order to elucidate our problem, it therefore seems convenient to
+restrict our considerations for a while to the study of plants. There
+exist very many external formative stimuli in the morphogenesis of
+vegetation: would it then be possible to regard every effect of such
+an external formative stimulus as a real morphological adaptation?
+No; for that would not meet the point. The general *harmony* of form
+is indeed concerned if gravity forces roots to shoot forth below at a
+spot where they can enter the ground, or if light induces branches and
+leaves to originate at places where they can obtain it for assimilation;
+but gravity and light themselves are mere formative stimuli--of the
+localising type--in these instances, for they relate only to the
+individual production of form, not to the functioning of already
+existing form. We therefore are warned not to confuse the effects of
+formative stimuli from without with real adaptive effects until we have
+fully analysed the particular case.
+
+We have drawn a sharp line between causes and means of morphogenesis,
+applying the term “means” to those conditions of the morphogenetic
+process which relate neither to the specificity nor to the localisation
+of its constituents, though they are necessary for the accomplishment
+of the process in the most thorough manner. Would it be possible to
+connect our new concept of an adaptation with our well-established
+concept of a means of morphogenesis in such a way that we might speak
+of a morphological “adaptation” whenever any specific feature about
+morphogenesis proves to be immediately dependent for its success on some
+specific means, though it does not owe its localisation to that means
+as its “cause”? It seems to me that such a view would also fall wide
+of the mark. It is well known, for instance, that the flowers of many
+plants never fully develop in the dark; light is necessary for their
+morphogenesis. Is, therefore, their growth in the presence of light to
+be called a morphological “adaptation” to light? Certainly not: they
+simply *cannot* originate without light, because they require it for
+some reason. It is precisely here that our conception of light as a
+“means” of morphogenesis is most fully justified. There are many[77]
+such cases; and there are still others of an apparently different
+type, but proving the same. All pathological forms produced in plants
+by animal parasites or by parasitic fungi could hardly be called
+adaptations, but must be attributed to some abnormality of means or of
+stimuli. It may be that the organism reacts as well as possible in these
+cases, and that if it reacted otherwise it would die--we know absolutely
+nothing about this question. But even then there would only be some sort
+of regulation *in* the process of pathological morphogenesis, but *the
+process* itself could hardly be called adaptive.
+
+[77] Klebs has suppressed the reproductive phase of organisation
+altogether, in fungi as well as in flowering plants, or has made it
+occur abnormally early, merely by changing the “external conditions”
+and by altering the “internal” ones correspondingly. There is hardly
+anything like an adaptation in these cases, which, by the way, offer
+certain difficulties to analysis, as the boundaries between “cause” and
+“means” are not very sharp here.
+
+So far we have only learned what is not to be regarded as morphological
+adaptation. No response to external formative stimuli is in itself an
+example of adaptation, nor are processes dependent for their existence
+on any kind of condition or means to be called, simply because they are
+dependent on them, adaptations to those agents. What then, after all, is
+a morphological adaptation?
+
+Let us remember what the word adaptation is really to mean in our
+discussions: a state of functioning is adapted--a state of functioning
+must therefore have been disturbed; but as functioning itself, at least
+in plants, certainly stands in close relations to the medium, it follows
+that all adaptations are in the last resort connected with those factors
+of the medium which affect functioning. In being correctives to the
+disturbances of functioning they become correctives to the disturbing
+factors themselves.
+
+But again, the question seems to arise whether these factors of the
+medium, when they provoke an adaptation by some change that is followed
+by functional disturbance, do so in the capacity of “causes” or of
+“means,” and so it might seem that we have not gained very much so far
+by our analysis. The reproach, however, would not be quite justified,
+it seems to me: we indeed have gained a new sort of analytical concept,
+in the realm of causal concepts in general, by clearly stating the
+point that adaptations are related directly to functionality, and only
+indirectly, through functionality, to external changes. By the aid of
+this logical formulation we now are entitled to apply the term “cause,”
+in our restricted sense of the word, to every change of the medium
+which is followed by any sort of adaptation in regard *to itself*. Our
+definition stated that a “cause” is any one of the sum of necessary
+factors from without that accounts either for the localisation *or* for
+*the specification* of the effect, and the definition holds very well in
+this case. Indeed, the specification of the effect is determined *by*
+the outside factor in every case of an adaptation *to* it, by the mere
+*fact* of its being a specific adaptation to this specific factor.
+
+We must not forget that in this chapter we are not studying real
+individual morphogenesis as the realisation of what has been inherited,
+but that at present we regard morphogenesis proper as an accomplished
+fact. Morphogenesis proper has laid the general lines of organisation;
+and now adaptation during the functional life, so to speak, imposes a
+second kind of organisation upon the first. It is for that reason that
+the meaning of the word “cause” is now becoming a little different from
+what it was before.
+
+In order to study a little more in detail what has been discovered
+about morphological adaptation in animals and plants, let us separate
+our materials into two groups, one of them embracing adaptations with
+regard to functional changes from without, the other adaptations to
+those functional changes which come from the very nature of functioning.
+Almost all of our previous general considerations have applied to the
+former group, with which we shall now proceed to deal.
+
+
+ADAPTATIONS TO FUNCTIONAL CHANGES FROM WITHOUT[78]
+
+[78] Compare Herbst, *Biol. Centralbl.* 15, 1895; and Detto, *Die
+Theorie der direkten Anpassung*, Jena, 1904. A full account of the
+literature will be found in these papers.
+
+The differences between plants grown in very dry air, very moist air,
+and water, respectively, are most distinctly seen in all the tissues
+that assist in what is called transpiration, that is, the exchange of
+water-vapour between the plant and the medium, but especially in the
+epidermis and the conductive fibres, both of which are much stronger
+in plants grown in the dry. Indeed, it seems from experiments that
+transpiration is the most essential factor to which “adaptation” occurs
+in amphibious plants, though the changes of the mechanical conditions
+according to the medium also seem to have some sort of structural
+effect. If plants stand very deeply in water, the conditions of
+illumination, so important for assimilation in plants, may have been
+altered, and therefore much of the structural change can be attributed
+also to them. It is unimportant in our general question what is due to
+one of these factors and what to the other. That there is a real sort
+of adaptation cannot be doubtful; and the same is true, as experimental
+observations of the last few years have shown, with regard to the
+structural differences between so-called sun-leaves and shade-leaves
+of plants grown in the air: it has been actually shown here that the
+functional life of the former goes on better in the sun, of the latter
+better in the shade.
+
+It is very important to emphasise this point, as the adaptive character
+of all sorts of structural differences in plants dependent on light
+and on moisture has lately been denied, on the supposition that there
+is only a stopping of organogenesis in the case of the more simple,
+a continuance in the case of the more complicated modification, but
+nothing else. Indeed, all morphological adaptation has been conceived
+as only consisting in differences dependent upon the absence or the
+presence of necessary means or causes of development, and as offering
+no problem of its own. We have gained the right position from which
+to oppose this argument, it seems to me, in our formula that all
+adaptations do relate *not* directly *to* the agents of the medium,
+but to changes of functional states induced *by* those agents; that
+adaptations only *are* “adaptations” by being correctives to the
+functional state.
+
+There simply *is* an “adaptation” of structure in *such* a sense in all
+the cases we have mentioned. We can say neither more nor less. Granted
+that one of the outside factors which comes into account is merely a
+necessary “means”: then why is the histological consequence of the
+presence of the means an actual adaptation to it as far as its relation
+to functioning is concerned--why is the consequence of its absence also
+an adaptation to this absence in its relation to functioning? Why, to
+complete the series, is the degree of the consequence of its presence an
+adaptation to the degree of its presence?
+
+All these relationships, which are so many facts, have been absolutely
+overlooked by those who have been pleased to deny morphological
+adaptation to functional changes from without.
+
+To do full justice to them we may speak of “primary” regulative
+adaptations in all the cases mentioned above, applying the word
+“primary,” just as was done with regard to restitutions, to the fact
+that there is some sort of regulation *in* the normal connection of
+processes. We reserve the title of “secondary adaptations” for cases
+such as those described, for instance, by Vöchting,[79] where not
+merely one and the same tissue originates adaptively with regard to the
+degree of its normal functioning, but where a profound disturbance
+of all functioning connections, due to the removal of portions of the
+organisation, is followed by histological changes at absolutely abnormal
+localities; that is, where a real change of the *kind* of functioning
+is the consequence of the adaptation. It, of course, will be found very
+difficult to discriminate such phenomena from real restitutions, though
+logically there exists a very sharp line between them.
+
+[79] Vöchting (*Jahrb. wiss. Bot.* 34, 1899) forced the bulbs of
+plants to become parts of the stem, and parts of the stem to form
+bulbs; in both cases the most characteristic changes in histology
+could be observed, being in part adaptations, but in part restitutions
+of the proper type. (See also my *Organische Regulationen*, 1901, p.
+84.) A true and simple instance of a “secondary adaptation” seems to
+be furnished in a case described by Boirivant. In *Robinia* all the
+leaflets of a leaf-stalk were cut off: the leaf-stalk itself then
+changed its structure in order to assist assimilation, and also formed
+real stomata.
+
+A few more concrete instances may now close this account of adaptation
+to functional changes coming from without. Though almost all the
+adaptive characters in the aquatic forms of amphibious plants represent
+a less complicated state of organisation than the corresponding
+structures in their terrestrial forms, and therefore have wrongly
+been regarded as simply due to a stopping of morphogenesis for want
+of necessary means, yet there are a few of them that are positive
+complications in comparison with the land-forms: the so-called
+aërenchyme, especially well developed in the water-form of *Jussiaea*
+is such an instance. This tissue stands in the direct service of
+respiration, which is more difficult to be accomplished under water than
+ordinarily, and represents a true adaptation to the altered function.
+
+Among animals there is only one well-studied instance of our first type
+of adaptive morphological characters. *Salamandra atra*, the black
+salamander, a species which only inhabits regions at least two thousand
+feet above sea-level, does not bring forth its young until metamorphosis
+has taken place. The larvae, however, may be removed from the mother’s
+body at an earlier stage and forced to complete their development in
+water. Under these circumstances, as was shown in an excellent memoir
+by Kammerer,[80] they will change the whole histological type of their
+gills and skin in order to meet the new functional conditions. The
+change of the conditions of functioning is very severe here, for whereas
+the gills had served for nutrition and respiration in the uterus--by
+a process of endosmosis--they now serve for respiration only, and, of
+course, are surrounded by quite an abnormal chemical medium.
+
+[80] *Arch. Entw. Mech.* 17, 1904.
+
+
+TRUE FUNCTIONAL ADAPTATION[81]
+
+[81] Roux, *Gesammelte Abhandlungen*, vol. i. 1895; in particular, *Der
+Kampf der Teile im Organismus*, Leipzig, 1881.
+
+But all other cases of morphological adaptation among animals, and
+several in the vegetable kingdom too, belong to our second group of
+these phenomena, which in our analytical discussion we have called
+adaptations to functional changes that result from the very nature
+of functioning, and which we shall now call by their ordinary name,
+“functional adaptation.”
+
+It was Roux who first saw the importance of this kind of organic
+regulation and thought it well to give it a distinguishing name. *By
+functioning the organisation of organic tissues becomes better adapted
+for functioning.* These words describe better than any others what
+happens. It is well known that the muscles get stronger and stronger the
+more they are used, and that the same holds for glands, for connective
+tissue, etc. But in these cases only quantitative changes come into
+account. We meet with functional adaptations of a much more complicated
+and important kind, when for instance, as shown by Babák,[82] the
+intestine of tadpoles changes enormously in length and thickness
+according as they receive animal or vegetable food, being nearly twice
+as long in the second case. Besides this the so-called mechanical
+adaptations are of the greatest interest.
+
+[82] *Arch. Entw. Mech.* 21, 1906. By a very detailed comparative study
+Babák was able to prove that it is the plant proteids to which the
+effect of vegetable food is chiefly due; thus we have an adaptation
+to digestibility. Mechanical circumstances are only of secondary
+importance. (See also Yung.)
+
+It has long been known, especially from the discoveries of Schwendener,
+Julius Wolff, and Roux, that all tissues whose function it is to resist
+mechanical pressure or mechanical tension possess a minute histological
+structure specially suitable to their requirements. This is most
+markedly exhibited in the stem of plants, in the tail of the dolphin, in
+the arrangements of the lime lamellae in all bones of vertebrates. All
+these structures, indeed, are such as an engineer would have made them
+who knew the sort of mechanical conditions they would be called upon to
+encounter. Of course all these sorts of mechanically adapted structures
+are far from being “mechanically explained,” as the verbal expression
+might perhaps be taken to indicate, and as indeed has sometimes been the
+opinion of uncritical authors. The structures exist *for* mechanics,
+not *by* it. And, on the other hand, all these structures, which we
+have called mechanically “adapted” ones, are far from being mechanical
+“adaptations,” in our meaning of the word, simply because they are
+“adapted.” Many of them indeed exist previous to any functioning, they
+are for the most part truly inherited, if for once we may make use of
+that ambiguous word.
+
+But, the merely descriptive facts of mechanical adaptedness having been
+ascertained, there have now been discovered real mechanical processes
+of adaptations also. They occur among the statical tissues of plants,
+though not in that very high degree which sometimes has been assumed
+to exist; they also occur in a very high perfection in the connective
+tissue, in the muscles and in the bone tissue of vertebrates. Here
+indeed it has proved possible to change the specific structure of the
+tissue by changing the mechanical conditions which were to be withstood,
+and it is in cases of healing of broken bones that these phenomena have
+acquired a very great importance, both theoretically and practically:
+the new joints also, which may arise by force of circumstances,
+correspond mechanically to their newly created mechanical function.
+
+So far a short review of the facts of “functionelle Anpassung.” They
+seem to prove that there does exist a morphological adaptation to
+functional changes which result from the very nature of functioning. In
+fact, the actual state of all functioning tissue, the intensity of its
+state of existence, if you care to say so, may be said to be due to the
+functioning itself: the so-called atrophy by inactivity being only one
+extreme of a very long line of correspondences.[83]
+
+[83] Atrophy of muscles by inactivity is not to be confused with atrophy
+by cutting the motor nerve; the latter is very much more complete.
+
+We now, of course, have to ask ourselves if any more intimate analysis
+of these facts is possible, and indeed we easily discover that here
+also, as in the first of our groups of morphological adaptations,
+there are always single definite agents of the medium, which might be
+called “causes” or “means” of the adaptive effects, the word “medium”
+being taken as embracing everything that is external to the reacting
+cells. But of course also here the demonstration of single formative
+agents does not detract in the least from the adaptive character of
+the reaction itself. So we may say, perhaps, that localised pressure
+is the formative stimulus for the secretion of skeleton substance at a
+particular point of the bone tissue, or of the fibres of the connective
+tissue; the merely quantitative adaptations of muscles might even
+allow of a still more simple explanation.[84] But adaptations remain
+adaptations in spite of that; even if they only deserve the name of
+“primary” regulations.
+
+[84] Loeb has advocated the view that the “adaptive” growth of working
+muscles is simply due to the presence of a greater number of molecules
+in their protoplasm, muscular activity being generated by a process of
+chemical decomposition.
+
+
+THEORETICAL CONCLUSIONS
+
+We have stated in the analytical introduction to this chapter and
+elsewhere, that functional changes, which lead to morphological
+adaptations of both of our groups, may arise not only from changes of
+factors in the medium, but also from a removal of parts. As such removal
+is generally followed by restitution also, it is clear that restitutions
+and adaptations very often may go hand in hand, as is most strikingly
+shown in a fine series of experiments carried out by Vöchting, which we
+have already alluded to. Here again I should like to lay the greatest
+stress upon the fact that, in spite of such actual connections,
+restitutions and adaptations always have been separated from another
+theoretically, and that the forms are never to be resolved into sums
+of the latter. Such a view has been advocated by some recent authors,
+especially by Klebs, Holmes, and Child:[85] it is refuted I think by the
+simple fact that the first phase of every process of restitution, be it
+regeneration proper or be it a sort of harmonious differentiation, goes
+on without functioning at all, and only *for* future functioning.[86]
+
+[85] What has been really *proved* to exist by the very careful studies
+carried out by Child, is only certain cases of functional adaptation
+to mechanical conditions of the strictest kind, and relating to the
+general mobility only, but nothing more; such adaptations can be said to
+accompany restitution. See, for instance, *Journ. exp. Zool.* 3, 1906,
+where Child has given a summary of his theory.
+
+[86] Even in Vöchting’s experiments (see page 174, note 1), in which
+adaptations are mixed with true restitutions in the closest possible
+manner, a few phenomena of the latter type could most clearly be
+separated. The stimulus which called them forth must have been one of
+the hypothetic sort alluded to in a former chapter (see page 113). The
+best instances of true restitutions were offered in those cases, where,
+after the removal of all the bulbs, typical starch-storing cells were
+formed without the presence of any starch.
+
+And there has been advocated still another view in order to amplify
+the sphere of adaptation: all individual morphogenesis, not only
+restitution, is adaptation, it has been said. In its strictest form
+such an opinion of course would simply be nonsense: even specific
+adaptive structures, such as those of bones, we have seen to originate
+in ontogeny previous to all specific functions, though for the help
+of them, to say nothing of the processes of the mere outlining of
+organisation during cleavage and gastrulation. But they are “inherited”
+adaptations, it has been answered to such objections. To this remark we
+shall reply in another chapter. It is enough to state at present that
+there *is* a certain kind of, so to speak, architectonic morphogenesis,
+both typical and restitutive, previous to specific functioning
+altogether.
+
+If now we try to resume the most general results from the whole field
+of morphological adaptations, with the special purpose of obtaining new
+material for our further philosophical analysis, we have reluctantly to
+confess that, at present at least, it does not seem possible to gather
+any new real proof of life-autonomy, of “vitalism,” from these facts,
+though of course also no proof against it.
+
+We have stated that there is in every case of both our types of
+adaptive events a correspondence between the degree of the factor
+to which adaptation occurs, and the degree of the adaptive effect.
+We here may speak of an *answering* between cause and effect with
+regard to adaptation, and so perhaps it may seem as if the concept of
+an “answering reaction” (“Antwortsreaktion”), which was introduced
+into science by Goltz[87] and which is to play a great part in our
+discussions of next summer, may come into account: but in our present
+cases “answering” only exists between a simple cause and a simple effect
+and relates almost only to quantity and locality. There is therefore
+lacking the most important feature, which, as will be seen, would have
+made the new concept of value.
+
+[87] *Beiträge zur Lehre von den Functionen der Nervencentren des
+Frosches*, Berlin, 1869.
+
+We only, I believe, can state the fact that there *are* relations
+between morphogenetic causes and effects which *are* adaptations, that
+functional disturbances or changes are followed by single histogenetic
+reactions from the organism, which are compensations of its disturbed or
+changed functional state. We are speaking of facts here, of very strange
+ones indeed. But I feel unable to formulate a real proof against all
+sorts of mechanism out of these facts: there *might* be a machine, to
+which all is due in a pre-established way. Of course we should hardly
+regard such a machine as very probable, after we have seen that it
+*cannot* exist in other fields of morphogenesis. But we are searching
+for a new and independent proof; and that is indeed not to be found
+here.[88]
+
+[88] The “secondary adaptations” observed by Vöchting are too
+complicated and too much mingled with restitutions to allow any definite
+analysis of the fact of the “secondary adaptation” as such.
+
+At present it must be taken as one of the fundamental *facts* of the
+organogenetic harmony, that the cells of functioning tissues do possess
+the faculty of reacting to factors which have changed the state of
+functioning, in a way which normalises this state histologically. And
+it is a fact also that even cells, which are not yet functioning but
+are in the so-called embryonic or indifferent condition contributing to
+the physiological completion of the tissue, react to factors embracing
+new functional conditions of the whole in a manner which leads to an
+adaptation of that whole to those conditions.
+
+This is a very important point in almost all morphological adaptation,
+whether corresponding to functional changes from without or resulting
+from the very nature of functioning. In fact, such cells as have already
+finished their histogenesis are, as a rule, only capable of changing
+their size adaptively, but are not able to divide into daughter-cells
+or to change their histological qualities fundamentally; in technical
+terms, they can only assist “hypertrophy” but not “hyperplasia.” Any
+adaptive change of a tissue therefore, that implies an increase in the
+number of cellular elements or a real process of histogenesis, has to
+start from “indifferent” cells, that is to say, cells that are *not yet*
+functioning in the form that is typical of the tissue in question; and,
+strange to say, these “embryonic” cells--*i.e.* the “cambium” in higher
+plants and many kinds of cells in animals--*can* do what the functional
+state requires. It is to be hoped that future investigations will lay a
+greater stress upon this very important feature of all adaptation.
+
+
+2. PHYSIOLOGICAL ADAPTATION[89]
+
+[89] General literature: Fröhlich, *Das natürliche
+Zweckmüssigkeitsprincip in seiner Bedeutung für Krankheit und Heilung*,
+1894. Driesch, *Die organischen Regulationen*, 1901. A. Tschermak, “Das
+Anpassungsproblem in der Physiologie der Gegenwart,” in a collection
+of papers in honour of J. P. Pawlow, St. Petersburg, 1904. Bieganski,
+“Ueber die Zweckmässigkeit in den pathologischen Erscheinungen,” *Annal.
+d. Naturphil.* 5, 1906. Among the general text-books of physiology those
+by Pfeffer (*Pflanzenphysiologie*, 1897-1904) and von Bunge (*Lehrbuch
+d. Phys. d. Menschen*, 1901) are the fullest on the subject of
+“regulations.” See also different papers on general pathology by Ribbert.
+
+It is but a step from morphological adaptations to adaptations in
+physiology proper. The only difference between regulations of the
+first type and those which occur in mere functioning is, that the
+resulting products of the regulation are of definite shape and therefore
+distinctly visible in the first case, while they are not distinctly
+visible as formed materials but are merely marked by changes in chemical
+or physical composition in the latter.
+
+Metabolism, it must never be forgotten, is the general scheme within
+which all the processes of life in a given living organism go on; but
+metabolism means nothing else, at least if we use the word in its
+descriptive and unpretentious meaning, than change in the physical
+or chemical characteristics of the single constituents of that
+organism. In saying this, we affirm nothing about the physical or
+chemical nature of the actual processes leading to those physical or
+chemical characteristics, and by no means are these “processes” *a
+priori* regarded as being physical or chemical *themselves*: indeed,
+we have learned that in one large field, in the differentiation of
+our harmonious systems they certainly are not. Now, if the metabolism
+does not end in any change of visible form, then true physiological
+processes, or more particularly physiological regulations, are going on
+before us. But we are dealing with morphogenetic events or regulations,
+if the result of metabolism is marked by any change in the constituents
+of form. This however may depend on rather secondary differences as to
+the nature of regulation itself, and any kind of metabolism may really
+be of the regulatory type, whether we actually see its result as a
+constituent of form, *e.g.* owing to the production of some insoluble
+compound, or whether we do not.
+
+I do not mean to say that these are the only differences between mere
+physiological activities or regulations and organogenesis proper, as an
+originating of typical form-combination; but if we regard, as we do in
+this chapter, the given organisation of a living being as a substratum
+of its functional life, morphological and physiological adaptations are
+indeed of almost the same logical order.
+
+We had best therefore begin our discussions with a recapitulation of
+our problem. We are studying adaptations in functioning--that means we
+want to know how the organism behaves with regard to any change which
+may take place in its functional state. We apply the term regulation,
+or in particular adaptation, to any kind of reaction on the part of the
+organism which re-establishes the normal state of functioning, and we
+now want to learn to what degree such adaptations exist in the field of
+physiology.
+
+
+SPECIFIC ADAPTEDNESS *NOT* “ADAPTATION”
+
+It is important to keep well in mind our strictly formulated theme, as
+by doing so we shall be able to exclude at once from our materials a
+large group of phenomena which occasionally have been called regulations
+by physiological authors, but which, in fact, are not of the adaptation
+type and therefore cannot be said to afford those problems which
+possibly might have been expected. Typical peculiarities in functional
+life cannot be called “regulations” for this very reason. If, for
+instance, the organism selects specific amounts of specific kinds of
+organic food or of salts out of the combinations of salts or organic
+food normally offered to it in the medium, as indeed is most typically
+shown for instance by the roots of plants, there cannot be said to occur
+a “regulation” or “adaptation” with regard to the permeability of the
+cell, nor is it strictly a case of “regulation,” if so-called selective
+qualities are discovered in the processes of secretion, say of the
+epithelium of the kidney.
+
+All these facts are typical and specific peculiarities in functioning
+which are duly to be expected, where a very typical and specific
+organisation of the most elaborated kind exists. Indeed, after studying
+such an organisation we must not be astonished that functions in
+organisms follow lines which certainly they would not have taken without
+it. Take the fact which is quoted very often, that the migration of
+compounds or of ions in the organisms can happen quite contrary to all
+the laws of osmosis, from the less concentrated to the more concentrated
+side of a so-called “membrane.” There *is* no simple “membrane” in the
+organism, but a complicated organisation of an almost unknown character
+takes its place, and nothing, indeed, is against the assumption that
+this organisation may include factors which actually drive ions or
+compounds to the side of higher concentration, which indeed drive them
+by “doing work,” if we like to speak in terms of energy; and these
+factors included in organisation may very well be of a true physical or
+chemical nature.[90]
+
+[90] According to investigations of the last two years, the physics of
+colloids seems to play as important a part in physiology as osmosis
+does; we here meet “means” of functioning just as we have already had
+“means” of organogenesis.
+
+I lay great stress upon these statements, as I should like to be as
+careful as possible in the admission of anything like a “proof” of
+vitalism. It was want of scientific criticism and rigid logic that
+discredited the old vitalism; we must render our work as difficult as
+possible to ourselves, we must hold the so-called “machine theory” of
+life as long as possible, we must hold it until we are really forced to
+give it up.
+
+In a more general form we now can sum up our discussion by saying: There
+never are adaptations in physiology, requiring any special analysis,
+where there are only complications or even apparent deviations from the
+purely physico-chemical type of events which are, so to say, statical,
+*i.e.* fixed in quantity or quality, however peculiar or typically
+complicated they may be; all such peculiarities indeed, may properly
+be called “adapted,” that is to say, very well fitted to perform a
+specific part in the service of normal general functioning, and they
+are “adapted” to their part by virtue of a certain “adaptedness” of the
+organisation; but they are not “adaptations” in any sense of the word.
+
+
+PRIMARY AND SECONDARY ADAPTATIONS IN PHYSIOLOGY
+
+We approach the subject of true adaptations, that is, of adapting
+processes, as soon as any kind of variation in functioning occurs which
+corresponds to a variation of any factor of the medium in the widest
+sense. But even here our work is by no means done by simply showing
+such a correspondence of outer and inner variations. We know very well
+already, from our former studies, that now we are faced by a further
+problem, that we are faced by the question whether we have to deal with
+simple primary kinds of adaptations or with the far more important
+secondary ones.
+
+As the discrimination between primary and secondary regulations proves
+indeed to be of first-rate importance, you will allow me, I hope, to
+summarise our chief analytical statements regarding them in a most
+general form. We call primary regulatory any kind of morphogenetic or
+functional performance, which, by its very intimate nature, always
+serves to keep the whole of organisation or of functions in its normal
+state. We call secondary regulations all features in the whole of
+morphogenesis or of functioning which serve to re-establish the normal
+state after disturbances along lines which are outside the realm of
+so-called normality. This analytical discrimination will help us very
+much to a proper understanding of physiology. But before we turn to
+apply our definitions to actual facts, another preliminary problem has
+to be solved.
+
+
+ON CERTAIN PRE-REQUISITES OF ADAPTATIONS IN GENERAL
+
+We are thinking of the general and important question, what types of
+adaptations may be expected in the field of physiology and whether
+there may be certain classes of regulatory events which possibly might
+be expected to occur in the organism on *a priori* grounds, but which,
+nevertheless, are to be regarded as impossible after a more intimate
+analysis of its nature, even at the very beginning? Or, in other words,
+to what kinds of changes of the medium will an organism be found able or
+unable to adapt itself?
+
+We know that the *state of functioning* must be altered in order to call
+forth any sort of adaptation at all. Now, there can be no doubt that *a
+priori* it would seem to be very useful for the organism, if it never
+would let enter into its blood, lymph, etc., be it through the skin or
+through the intestine, any chemical compound that would prove to be
+a poison afterwards. In fact, a man, judging on the principle of the
+general usefulness of all the phenomena of the living, might suppose
+that there would exist a sort of adaptation against all poisons to the
+extent that they would never be allowed to enter the real interior of
+the body. We know that such reasoning would be incorrect. But we also
+can understand, I suppose, that an *a priori* analysis of a more careful
+kind would have reasoned differently. How could the functional state
+of the organism be changed, and how, therefore, could adaptation be
+called forth by any factor of the medium which had not yet entered the
+organism, but was only about to enter it? Not at all therefore is such
+a regulation to be expected as we have sketched; if there is to be any
+adaptation to poisons, it only can occur after the poison has really
+acted in some way, and in this case we shall indeed find regulations.
+
+You may perhaps regard this discussion as a little too academical
+and hair-splitting, but here again it was for the sake of ensuring a
+perfectly sound foundation of our chief principles that I undertook it.
+Very often, indeed, the question has been raised by the defenders of a
+mechanistic theory of life, Why then did the organisms not reject all
+poisons from the very beginning? We now may reply to that only--how
+*could* they do so? How could they “know” what is a poison and what is
+not, unless they had experienced it?--if we are allowed for a moment to
+use very anthropomorphistic language.
+
+We repeat, therefore, that the functional conditions of the organism
+must have been actually changed in order that an adaptation may occur.
+Nothing is more essential to a clear understanding of our problems than
+to keep fully in mind the exact sense of this definition.
+
+
+ON CERTAIN GROUPS OF PRIMARY PHYSIOLOGICAL ADAPTATIONS
+
+*General Remarks on Irritability.*--Turning now to more special groups
+of problems concerning physiological adaptations, let us begin with the
+primary class of them, and let us first say a few words on a subject
+which occasionally has been regarded as the basis of physiological
+regulation in general. I refer to a most important fact in the general
+physiology of irritability. Irritability of any kind is known to be
+re-established, after it has been disturbed by the process of reacting
+to the stimulus, and in certain cases, in which two different--or rather
+two opposite--kinds of reactions are possible on the same substratum,
+which increase with regard to one process whilst decreasing at the same
+time with regard to the other. The irritability of the muscle or of the
+leaves of *Mimosa* is a very good instance of the first case, whilst the
+second more complicated one cannot be illustrated better than by what
+all experience has taught us about the irritability of the retina. The
+retina is more irritable by green rays and less by red ones the more
+it has been stimulated by the latter, and more sensitive to light in
+general the more it has been exposed to darkness; and something very
+similar is true, for instance, as regards phototactic irritability in
+plants, all these phenomena being in relation to the so-called law of
+Weber.[91]
+
+[91] I only mention here that certain modern psychologists have assigned
+the true law of Weber to the sphere of judgment and not of sensation. If
+applied to objective reactions only, in their dependence on objective
+stimuli, it, of course, becomes less ambiguous, and may, in a certain
+sense, be said to measure “acclimatisation” with regard to the stimulus
+in question. The mathematical analogy of the law of Weber to the most
+fundamental law of chemical dynamics seems very important.
+
+As to “acclimatisation” in the more usual meaning of the word, with
+regard to a change of the general faculty of resisting certain agents
+of the medium, “immunity” proper is to form a special paragraph of what
+follows, and to “acclimatisation” towards different degrees of salinity
+(in algae or fishes) some special remarks will also be devoted on a
+proper occasion. There remains only “acclimatisation” to different
+temperatures; but on this topic not much more than the fact is known
+(see Davenport, *Arch. f. Entw. Mech.* 2, p. 227). “Acclimatisation”
+does not allow of a sharp general definition; it may be the result of
+very *different* kinds of adaptations in our sense of the word.
+
+It seems to me that there would be little difficulty in harmonising the
+phenomenon of the inversion of irritability with the so-called principle
+of the “action of masses” and with the laws of certain “reversible”
+processes well known in chemistry. As to the simple fact of the
+re-establishment of irritability after stimulation has occurred, or,
+in certain other cases, the fact that in spite of permanent stimulation
+irritability seems to exist permanently also, physical analogies or even
+explanations might very well be found.[92]
+
+[92] I should think that the problem of the re-establishment of
+irritability, in principle at least, arises even when there is not a
+trace of so-called “fatigue” or of a “refractory period.” The process
+of restoring may be so rapid as not to be noticeable, nevertheless some
+sort of restoring is to be postulated. We may say the “irritability” of
+an elastic ball is re-established by its elasticity. A certain analogy
+to this case may perhaps be found in the muscle. But the irritability
+of nerves with respect to nervous conduction, and of glands with
+respect to secretion, or of the articulations of *Mimosa* may be well
+understood, hypothetically at least, if we assume that the ordinary
+course of metabolic events is apt in itself to lead to a certain state
+or condition of the organs in question upon which their irritability
+is based. Certain general conditions of functioning, as for instance
+the presence of oxygen for the contraction of the muscle, would better
+be looked upon as necessary “means” of functioning than as being part
+of irritability as such. “Fatigue,” of course, may also be due to
+the absence of such “means” or to abnormal conditions originated by
+functioning itself.
+
+If now we ask whether there is anything like an adaptation appearing in
+the general characteristics of irritation and irritability, it seems to
+me that we may answer the question in an affirmative manner, as far as
+primary regulation comes into account. We, certainly, have not studied
+any abnormal regulatory lines of general functioning, we only have
+studied general functioning itself; but, indeed, there was a certain
+sort of regulation *in* functioning. Of course, by showing that one
+of the most general features of all functioning is primary-regulatory
+in itself, we do not deny the possibility of many specific functions
+in which real secondary regulations actually do exist. Nothing indeed
+is asserted about the *specific* character of functioning in its
+different types, by proving that one of the *general* features of *all*
+functioning may comparatively easily be understood. It seems to me that
+this important logical point has not always received the attention it
+deserved.
+
+*The Regulation of Heat Production.*[93]--Having finished our
+introductory remarks we now turn to the proper study of special
+physiological functioning with regard to its adaptive side, and begin
+with the most simple cases.
+
+[93] Rubner, *Die Gesetze des Energieverbrauches bei der Ernährung*,
+Leipzig u. Wein, 1902.
+
+The so-called “regulation of heat” in warm-blooded vertebrates is an
+instance of a special function which can be said to be regulatory in
+itself. There exists a normal blood heat for each species, which is
+maintained no matter whether the temperature of the medium rise or fall.
+It might seem at first as if in this case there were a little more
+of an adaptive regulation than only its well-known primary type; no
+reversion, one might say, of the direction of one and the same process
+occurs in the regulation of heat production, but one kind of process
+is called into action if it is necessary to raise the temperature, and
+another whenever it is necessary to lower it. Even in the dilatation
+and constriction of capillary vessels there are different nerves
+serving for each operation respectively, and far more important are the
+increasing of transpiration for cooling, the increasing of combustion
+for heating--two radically different processes. But, nevertheless, there
+is a certain unity in these processes, in so far as a specific locality
+of the brain has been proved to be the “centre” of them all; it is to
+this centre of course that the analysis of heat production considered as
+a kind of regulation or adaptation must be directed. Such an ultimate
+analysis, it seems to me, would have to classify heat regulation under
+the primary type of adaptations in physiology without any restriction.
+The centre acts in one sense or in the other, if stimulated by any
+temperature beyond a very limited range, and it is in the action of the
+centre that the “regulation” of heat consists.[94]
+
+[94] The phenomenon of fever we leave out of account here; it is
+regarded by some as regulation, by others as a disturbance of heat
+regulation. Of course, if the first view should ever prove to be the
+right one, fever might be classified among the real regulations of the
+secondary type.
+
+*Primary Regulations in the Transport of Materials and Certain Phenomena
+of Osmotic Pressure.*--Very similar phenomena of regulation are present
+in many processes concerned in the whole of metabolism. Let us consider
+for a moment the migration of materials in plants. Whenever any compound
+is used at a certain place, a permanent afflux of this compound to
+that place sets in from all possible directions. No doubt this is a
+“regulation,” but it is also the function itself, and besides that,
+a very simple function based almost entirely on well-known laws of
+physical chemistry. And in other cases, as in the ascent of water to
+the highest tops of our trees, which purely physical forces are said to
+be insufficient to explain, we can appeal to the unknown organisation
+of many cells, and there is nothing to prevent our attributing to these
+cells certain functions which are, if you like to say so, regulatory
+in themselves. Among other facts of so-called regulations there is the
+stopping of metabolic processes by an accumulation of their products:
+as, for instance, the transformation of starch into sugar is stopped,
+if the sugar is not carried away. Of course that is a regulation, but
+it again is an intrinsic one, and it is one of the characteristics of
+reversible chemical processes to be stopped in that way. I know very
+well that in this particular case a certain complication is added by
+the fact that it is a so-called ferment, the diastase, which promotes
+the transformation of starch into cane-sugar, and that this ferment is
+actively produced by the organism: but even its production would not
+prove that any real kind of secondary regulation exists here, if nothing
+more were known about such an active production than this single case.
+
+In a special series of experiments almost all carried out in Wilhelm
+Pfeffer’s botanical laboratory at Leipzig, an attempt has been made
+to discover in what manner the cells of plants are able to withstand
+very high abnormalities of the osmotic pressure of the medium--that is
+to say, very great changes in the amount of its salinity. That many,
+particularly the lower plants, are able to stand such changes had been
+ascertained already by the careful examinations of Eschenhagen; but
+recent years have given us a more profound insight into what happens.
+Von Mayenburg[95] has found that sundry of the species of *Aspergillus*,
+the common mould, are able to live in very highly concentrated solutions
+of several salts (KNO_3 and Na_2SO_4). They were found to regulate
+their osmotic pressure not by taking in the salts themselves, but by
+raising the osmotic pressure of their own cell sap, producing a certain
+amount of osmotically active substances, probably carbohydrates. If
+in this case it were possible to assume that the osmotic pressure of
+the medium were the real stimulus for the production of the osmotic
+substances in the cell, stimulus and production both corresponding
+in their degree, we should be entitled to speak of a primary though
+physiological[96] regulation only; and it seems to me that despite the
+discoveries of Nathansohn that certain algae and cells of higher plants
+are able to change the permeability of their surfaces in a way which
+regulates the distribution of single salts or ions in the sap of their
+cells without any regard to pure osmotic equilibrium, such a simple
+explanation might be possible.[97]
+
+[95] *Jahrb. wiss. Bot.* 36, 1901.
+
+[96] Carbohydrates cannot be ionised, and therefore there is no doubt
+that in von Mayenburg’s experiments the organism itself is actively
+at work. As to compounds liable to ionisation, it has been noticed by
+Maillard that a certain regulatory character is contained simply in the
+physical fact that the degree of ionisation changes with concentration:
+decrease of concentration for instance would be followed by an increase
+of ionisation, and so the osmotic pressure may be preserved (*C. rend.
+Soc. Biol.* 53, 1901, p. 880).
+
+[97] In the different experiments of Nathansohn (*Jahrb. wiss. Bot.*
+38, 1902, and 39, 1903) the salinity of the medium was changed in such
+a way that there was in each case either an abnormal increase or an
+abnormal decrease in the concentration of one single ion necessary
+for metabolism. The cell was found to stand these abnormal changes in
+such a way that in the case of the increase of the concentration of
+the medium it did not allow more than a certain amount of the ion in
+question to come in, and that in the case of the decrease it did not
+allow more than a certain quantity of the ion to go out. It thus seems
+as if the permeability of the surface were adjusted to a certain minimum
+and to a certain maximum of every single ion or salt, the permeability
+being stopped from within to without, whenever the minimum, and from
+without to within, whenever the maximum is reached in the cell sap; both
+irrespective of proper physical osmotic equilibrium (“Physiologisches
+Gleichgewicht”). Thus, in fact, there only would be a case of primary
+regulation, nothing more. It would all appear rather similar to what
+occurs in the kidney. Of course we do not assert that our explanation is
+right, but it is possible and is at the same time the most simple, and
+it is our general practice always to prefer the most simple hypotheses.
+
+There are many regulation phenomena connected with osmotic pressure
+and permeability in animal physiology also, though at present they are
+not worked out as fully as possible. The works of Frédéricq, J. Loeb,
+Overton and Sumner[98] would have to be taken into account by any
+one who wished to enter more deeply into these problems. We can only
+mention here that permeability to water itself also plays its part, and
+that, according to Overton’s experiments, it is a kind of solubility
+of the media in the very substance of the cell surface on which all
+permeability and its regulation depend.
+
+[98] Many fishes are able to withstand great changes in the osmotic
+pressure of sea-water; the osmotic pressure of their body fluids, though
+never in a real physical equilibrium with the pressure of the medium,
+nevertheless may vary whenever the abnormal conditions of the latter
+exceed certain limits.
+
+*Chromatic Regulations in Algae.*--The phenomena of osmotic pressure and
+its regulation may be said to be the preliminaries of metabolism proper,
+conditions necessary for it to take place. Now there is another branch
+of such preliminaries to metabolism, in which the most interesting
+regulation phenomena have been lately discovered. It is well known that
+what is called assimilation in plants, that is, the formation of organic
+compounds out of carbon dioxide (CO_2) and water, occurs only in
+the light by means of certain pigments. This pigment is in all higher
+plants and in many others the green chlorophyll, but it may be different
+in certain species of algae, and can generally be said[99] to be of
+the colour complementary to the colour of those rays which especially
+are to be absorbed and to be used for assimilation. But here we have
+“adaptedness,” not adaptation. It was in some species of primitive
+algae, the *Oscillariae*, that Gaidukow[100] found a very interesting
+instance of an active regulation in the formation of pigments. These
+algae always assume a colour which corresponds to the accidental colour
+of the rays of the medium and is complementary to it; they become green
+in red light, yellow in blue light, and so on--that is, they always
+actively take that sort of colouring which is the most suitable to
+the actual case.[101] There indeed occurs a sort of complementary
+photography in these algae; but, though adaptive, it could hardly be
+said to exceed the limits of “primary phenomena.”
+
+[99] See Stahl, *Naturw. Wochenschrift*, N. F. 5, 1906, No. 19.
+
+[100] *Arch. Anat. Phys.*, Phys. Abt. Suppl., 1902.
+
+[101] The adaptive phenomena discovered by Gaidukow depend upon a real
+alteration in the formation of pigments. In the (primary) chromatic
+adaptation of pupae of Lepidoptera with respect to the colour of
+the ground they live upon, we only have the variable effects of
+pre-established chromatophores (Poulton, *Phil. Trans. London*, 178 B,
+1888; Merrifield, *Trans. Ent. Soc. London*, 1898). The same holds for
+chromatic adaptations in crabs (Gamble and Keeble, *Quart. Journ. Micr.
+Sci.* 43, 1900; Minkiewicz, *Arch. Zool. exp. et gén.* sér. 4, 7, notes,
+1907).
+
+*Metabolic Regulations.*--And now we enter the field of regulations in
+metabolism itself. There are two kinds of outside factors of fundamental
+importance for all metabolic processes: food is one, and oxygen is the
+other. And metabolism as a whole is of two different aspects also:
+it both serves for assimilation proper--that is, building up--and it
+supplies the energy for driving the functional machine. It is clear
+that food alone--together of course with the assimilating means of the
+organism, can account for the first type of metabolism, while both food
+and oxygen, or some sort of substitute for the latter, as in certain
+bacteria, supply functional energy. Of course we are not entitled to say
+that the importance of so-called oxidation or respiration is exhausted
+by its energetic rôle: it certainly is not, for if it were, the organism
+would only be stopped in its functions if deprived of oxygen but
+would not die. It seems that certain substances always arise in the
+metabolism, in the processes of decomposition, which have to be burnt up
+in order not to become poisonous. But we shall return to the phenomena
+of organic oxidation in another chapter of the book, and shall deal with
+them from a more general point of view.[102]
+
+[102] The theory of oxidation we have shortly sketched here was
+developed in chapter B. 5, of my *Organische Regulationen*. Recent
+discoveries of Winterstein’s (*Zeitschr. allg. Physiol.* 6, 1907)
+have given the strongest support to my hypothetic statements, and, in
+fact, can be said to have brought the doctrine of organic oxidation
+to a critical point. There can be no doubt that oxygen not only plays
+the “antipoisonous” rôle I had assigned to it, but that it is not
+even of such great importance for the supply of functional energy as
+former times had assumed. No doubt it serves to drive the functional
+machine, but decomposition of certain chemical constituents of the
+organism serves this purpose even more. The latter does so in the most
+fundamental and original manner, so to speak, whilst oxidation only
+burns up its products. Almost all elemental functions, in nerve-tissue
+at least, go on very well in the absence of oxygen, provided that
+certain “poisonous” substances, resulting from this anaërobic
+metabolism, are constantly removed. In normal conditions that is
+done by oxygen, and in doing so oxygen certainly assists the supply
+of energy, but it does not furnish the whole of it. The difference
+between so-called “aërobic” and “anaërobic” life almost completely
+disappears under such a view, and many so-called “regulations,” of
+course, disappear at the same time; there is no more “intramolecular
+respiration.”
+
+Let us now try to take a short survey of all the regulations discovered
+relating to the substitution of one kind of food for another. We have
+said that food serves in the first place as building material, in the
+second place as fuel. It only deserves brief mention that, as all recent
+investigations have shown, fats, carbohydrates, and albumen are equally
+well able to serve as fuel.[103]
+
+[103] But nevertheless albumen is not to be replaced altogether in
+vertebrates by fat or carbohydrate; it probably serves some special
+function besides combustion, even in the adult.
+
+It is in the state of fasting, *i.e.* in the case of a real absence of
+*all* nourishing materials, that the organism has proved to be capable
+of regulations of the most marked nature, with regard to the combustion
+of its own materials. Respiration, we know, must go on if death is to
+be avoided, and now indeed it has been found that this process attacks
+the different tissues of the organism subjected to fasting in such an
+order that, after the combustion of the reserves, the most unimportant
+tissues with regard to life in general are destroyed first, the most
+important ones last. Thus in vertebrates the nerve cells and the heart
+are preserved as long as possible; in infusoria it is the nucleus; in
+flatworms, as the very careful studies of E. Schultz[104] have lately
+shown, it is the nerve cells and the sexual cells which longest resist
+destruction, whilst almost all the rest of the organisation of these
+animals may disappear. I should not say that we can do very much with
+these facts at present in our theoretical discussion, but they are
+certainly witness of very astonishing adaptive powers.[105]
+
+[104] *Arch. Entw. Mech.* 18, 1904.
+
+[105] To a physiological friend of mine I owe the suggestion that it is
+the permanently functioning tissues which stand hunger better than the
+others, at least if the sexual cells might be regarded as capable of
+a *sécrétion interne* in all cases. Then the adaptations in the state
+of hunger might be said to be reduced in some degree to “functional
+adaptation.” But it must remain an open question, it seems to me,
+whether such a view may indeed hold in the face of the facts observed in
+*Planaria* and infusorians.
+
+We now turn to study the cases of a compensation of nourishments
+serving for the real building up of the organism. Albumen, we know, is
+absolutely indispensable for animals, even for adults, though nothing is
+known about the purpose it serves in the latter; its place can be taken
+of course by those less complicated compounds which result from its
+first decomposition, effected by pepsin and trypsin, but nothing else
+will do. The salts of sea-water, according to Herbst’s experiments, may
+only vary to a very small degree if the development of marine animals
+is to go on well; potassium may be replaced by caesium or rubidium,
+and that is all. Much the same is true of the salts necessary to
+plants. It will not surprise us very much to hear that algae can also
+be successfully fed with the potassium salts of organic compounds, and
+higher plants with acid amides or glucoses instead of carbonic acid, as
+those products are normal steps in their assimilation; and it may also
+be fairly easily understood that nitrogen can be offered in organic form
+instead of as a nitrate.
+
+It was in the group of fungi that really important adaptations with
+regard to the proper form-producing alimentation were first discovered,
+and these are of a very complicated kind indeed. Fungi are known to
+be satisfied with one single organic compound instead of the group of
+three--fat, carbohydrate and albumen--necessary for animals. Now Pfeffer
+showed that the most different and indeed very abnormal compounds were
+able to bring his subjects to a perfect growth and morphogenesis; and,
+moreover, he found that, if several kinds of such food were offered
+together, they were consumed quite indifferently as to their chemical
+constitution, but only with regard to their nutritive value: that sort
+of food which had produced a better growth than another when both
+were offered separately was found to save the latter from consumption
+whenever both were offered together.
+
+Here we are faced by one of the most typical cases of regulations in
+metabolic physiology: the organism is able to decompose compounds of
+the most different constitution, which have never been offered to it
+before; but nevertheless, it must remain an open question whether real
+“secondary” regulation has occurred, as nothing is known in detail about
+the single steps of metabolism in these fungi. There *might* be some
+ferments equally able to destroy different classes of compounds,[106]
+and that the most nutritive compound is used up first *may* be a
+question of physico-chemical equilibrium.
+
+[106] In all cases where fungi of the same species are able to live on
+different hosts, that is, to penetrate membranes of a different chemical
+character, a similar objection as to the “secondary” type of such a
+regulation may be made.
+
+That is almost all[107] that is actually known of adaptation with regard
+to the use of an abnormal food supply. Though important, it cannot be
+said to be very much. But could we expect very numerous regulations
+here at all after what we laid down in a former paragraph about the
+possibilities of adaptive regulation in general? The functional state
+must have been altered in order that such regulations may occur. Now
+there is no doubt that this state may be really altered only if an
+abnormal food has first been taken in altogether by the cell-protoplasm
+of the body-surfaces, but never if it has only entered the cavity of the
+intestine, which, strictly speaking, is a part of the exterior medium.
+Fungi indeed not only take in the abnormal food, but also know what
+to do with it, but all animals are obliged to treat first with their
+chemical secretions what happens to be present in their intestine, in
+order that it may be taken up by their living cells, and one hardly
+can wonder that these secretions are only formed in correspondence to
+a limited number of outside stimuli. In fact, as soon as we look upon
+what adaptive or regulatory work happens in metabolism *inside* the body
+interior, we meet, even in animals, regulations of a far more developed
+type.
+
+[107] The discovery of Weinland that adult dogs are able to produce
+“lactase” in their pancreas, whenever they are fed, quite abnormally,
+with milk-sugar, has recently been said to be vitiated by an analytical
+mistake.
+
+Discoveries of the last few years have taught us that almost all
+metabolic processes in the organism, including oxidation, are carried
+out by the aid of special materials, the so-called enzymes or
+ferments. These are known to exist in the most different forms even in
+the inorganic world. They are simply chemical compounds, of specific
+types, that bring about chemical reactions between two other chemical
+materials, which in their absence would either not go on at all or would
+go on very slowly. We cannot enter here into the much disputed chemical
+theory of what is called “catalysis”: we can only say that there is no
+objection to our regarding almost all metabolic processes inside the
+organism as due to the intervention of ferments or catalytic materials,
+and that the only difference between inorganic and organic ferments is
+the very complicated character of the latter and the very high degree of
+their specification.
+
+Such a statement, of course, does not say that all metabolism has proved
+to be of a chemical nature: the *action* of the ferment when produced
+is chemical, but we do not know at all *how* the ferment is produced;
+we only know that a high degree of active regulation is shown in this
+production. In fact, it has been proved in some cases, and probably will
+be proved in a great many more in the near future, that all metabolic
+ferments, whether they promote oxidation or assimilation proper or
+chemical decomposition, are produced in a regulatory manner with regard
+to the specific compound to be dissociated or to be built up. In this
+way the whole field of metabolism is really covered by “regulations.”
+Are they real “secondary” ones? Of course the regulatory correspondence
+applies to the process of *secretion* in the *first* place, not to the
+actual formation of the ferment inside the cell. The correspondence as
+to secretion, no doubt, is of the primary type; is there any secondary
+regulation with regard to the real *production* of the ferment? I am
+sorry that I cannot answer this question affirmatively. Nothing is
+*known* at present, even here, that really proves the existence of
+adaptation of the secondary type: there *might* be a sort of statical
+“harmony” at the base of it all, established before all functioning
+*for* functioning.[108]
+
+[108] Compare the excellent review of the subject by Bayliss and
+Starling in the *Ergebnisse der Physiologie*, 5, 1906, p. 664. The
+reader who misses here an analysis of the brilliant discoveries
+of Pawlow and his followers, relating to so-called “psychical and
+associative secretion,” will find these facts dealt with in another
+section of the book. These facts, indeed, would prove vitalism, it seems
+to me.
+
+The only facts of secondary metabolic regulations which are known at
+present have been found in combination with phenomena of restitution
+after real disturbances of organisation, where, indeed, numbers and
+numbers of regulatory changes of metabolism, both in animals and plants,
+have also been recorded. But there is not one case of a secondary
+regulation really known to affect pure metabolism alone.[109] This is a
+new indicium of the primacy of *form* in the organism.
+
+[109] It would be a true secondary metabolic regulation, if after the
+extirpation of one gland another different one were to assume its
+function. Nothing is known in this respect except a few rather doubtful
+observations about the interchange of functions between thymus and
+thyroid, except also the fact that the so-called lymph-glands increase
+in size after the extirpation of the spleen. Even here, of course, a
+sort of “restitution” would be included in adaptation proper.
+
+
+IMMUNITY THE ONLY TYPE OF A SECONDARY PHYSIOLOGICAL ADAPTATION
+
+There is only one class of physiological processes in which the type
+of the real secondary regulation occurs. The discoveries of the last
+twenty years have proved beyond all doubt, and future discoveries will
+probably prove even more conclusively, that the so-called *immunity*
+against diseases is but one case out of numerous biological phenomena
+in which there is an adaptive correspondence between abnormal chemical
+stimuli and active chemical reactions on the part of the organism and in
+its interior, exceeding by far everything that was formerly supposed to
+be possible in organic regulation.
+
+The adaptive faculty of the organism against inorganic poisonous
+substances[110] is but small comparatively, and is almost always due not
+to a real process of active regulation but to the action of substances
+pre-existing in the organism--that is, to a sort of adaptiveness but
+not adaptation. Metallic poisons, for instance, may be transformed into
+harmless compounds by being combined with albumen or sulphuric acid
+and thus becoming insoluble, or free acids may be neutralised, and so
+on; but all these processes go on to a certain extent only, and, as
+was mentioned already, are almost always the result of reactions with
+pre-existing materials. Only in a few cases is there any sort of true
+adaptation to metallic substances, such as sublimate and, in a very
+small degree, arsenic, comparable in some respects with the adaptation
+to abnormally high temperatures. The organism which has been accustomed
+to receive at first very small amounts, say, of sublimate, and then
+receives greater and greater amounts of this substance by degrees, will
+at the end of this treatment be able to stand a quantity of the poison
+that would have been instantly fatal if administered at the first
+dose.[111] But the explanation of this adaptation is not known in any
+case; there seems to be some similarity between it and the so-called
+histogenetic immunity against organic poisons.
+
+[110] A good review is given by E. Fromm, *Die chemischen Schutzmittel
+des Tierkörpers bei Vergiftungen*, Strassburg, 1903.
+
+[111] Davenport, *Arch. Entw. Mech.* 2, 1895-1896, and Hausmann,
+*Pflüger’s Arch.* 113, 1906.
+
+It is in the fight against animal and vegetable poisons, such as those
+produced by bacteria, by some plants and by poisonous snakes, that the
+true adaptation of the organism reaches its most astonishing degree.
+The production of so-called “anti-bodies” in the body fluids is not the
+only means applied against noxious chemical substances of this kind: the
+existence of so-called histogenetic immunity is beyond all doubt, and
+Metschnikoff[112] certainly was also right in stating that the cells
+of the organism themselves repel the attack of living bacteria. Cells
+of the connective tissue and the white blood cells, being attracted by
+them as well as by many other foreign bodies, take them in and kill
+them. This process, called “phagocytosis” is of special frequency among
+lower animals, but it also contributes to what is called inflammation
+in higher ones.[113] And there are still other kinds of defence against
+parasites, as for instance the horny or calcareous membranes, employed
+to isolate trichinae and some kinds of bacteria. But all this is of
+almost secondary importance as compared with the adaptive faculties of
+the warm-blooded vertebrates, which produce anti-poisonous substances in
+their lymph and blood.
+
+[112] *Leçons sur la pathologie comparée de l’inflammation*, Paris, 1902.
+
+[113] The other steps or phases in the process of inflammation have also
+been regarded as adaptive: the increased quantity of body fluid for
+instance is said to serve to dilute poisonous substances.
+
+It is impossible to say here[114] more than a few words about the
+phenomena and the theory of immunity proper, which have attained the
+dimensions of a separate science. Let me only mark those general points
+which are of the greatest theoretical interest. Discoveries of the most
+recent years have shown not only that against the “toxins” of bacteria,
+snakes, and some plants, the organism is able actively to produce
+so-called “anti-toxins”--that is, soluble substances which react with
+the toxins and destroy their poisonous character--whenever required,
+but that against any foreign body of the albumen group a specific
+reaction may occur, resulting in the coagulation of that body. But the
+destruction of the noxious substance or foreign albumen actually present
+is not all that is accomplished by the organism. “Acquired immunity”
+proper, that is, security against the noxious material for a more or
+less extensive period of the *future*, depends on something more. Not
+only is there produced as much of the so-called “anti-body” as is
+necessary to combine with the noxious, or at least foreign substances
+which are present, but *more* is produced than is necessary in the
+actual case. On this over-production depends all active immunity,
+whether natural or, as in some kinds of vaccination, artificial; and
+so-called “passive” immunity, obtained by the transfusion of the serum
+of an actively immune organism into another also depends upon this
+feature.[115]
+
+[114] See Jacoby, *Immunität und Disposition*, Wiesbaden, 1906.
+
+[115] *Collected Studies on Immunity by Ehrlich and his Collaborators*,
+translated by Ch. Bolduan, New York and London, 1906.
+
+This phenomenon in particular--the production of *more* of the
+antitoxin or the “precipitin” than is actually necessary--seems to
+render almost impossible any merely chemical theory of these facts. The
+reaction between toxin and antitoxin, albumen and precipitin is indeed
+chemical; it may in fact be carried out in a test-tube; but whether the
+production of the anti-body itself is also chemical or not could hardly
+be ascertained without a careful and unbiassed analysis. There can be
+no doubt that the well-known theory of Ehrlich,[116] the so-called
+theory of side-chains (“Seitenkettentheorie”) has given a great impulse
+to the progress of science; but even this theory, irrespective of its
+admissibility in general, is not a real chemical one: the concept of a
+regeneration of its so-called haptophore groups is a strictly biological
+concept.[117]
+
+[116] So-called genuine or innate immunity, in contrast to the immunity
+which is acquired, is of course a case of adaptedness only and not of
+adaptation. There also exists a high degree of specific adaptedness in
+some animals with regard to their faculty of coagulating blood. (See Leo
+Loeb, *Biol. Bull.* 9, 1905.)
+
+[117] We cannot do more than barely mention here the problem of the
+localisation of anti-body production. In general it seems to be true
+that anti-bodies are produced by those cells which require to be
+protected against toxins; that would agree with the general rule, that
+all compensation of the change of any functional state proceeds from the
+part changed in its function.
+
+And, indeed, here if anywhere we have the biological phenomenon of
+adaptation in its clearest form. There are very abnormal changes of the
+functional state of the organism, and the organism is able to compensate
+these changes in their minutest detail in almost any case. The problem
+of the specification of the reactions leading to immunity seems to me,
+as far as I can judge as an outsider, to stand at present in the very
+forefront of the science. There cannot be the slightest doubt that
+especially against all sorts of foreign albumens the reaction is as
+strictly specific as possible; but there are some typical cases of
+specificity in the production of antitoxins also. It is, of course,
+the *fact* of specific correspondence between stimulus and reaction,
+that gives to immunity its central position among all adaptations,
+no matter whether the old hypothesis of the production of specific
+anti-bodies proves tenable, or whether, as has been urged more recently
+by some authors, the anti-body is always the same but reacts differently
+according to the medium. In the latter case it would be the medium that
+is regulated in some way by the organism in order to attain a specific
+adaptedness.
+
+
+NO GENERAL POSITIVE RESULT FROM THIS CHAPTER
+
+But now let us look back to the sum of all the physiological reactions
+studied, and let us see if we have gained a new proof of the autonomy of
+life from our long chapter.
+
+We freely admit we have not gained any really new *proof*, but we may
+claim, I think, to have gained many indicia for the statement that
+the organism is not of the type of a machine, in which every single
+regulation is to be regarded as properly prepared and outlined.
+
+It is precisely in the field of immunity that such a machine-like
+preparation of the adaptive effects seems almost impossible to be
+imagined. How indeed could there be a machine, the chemical constituents
+of which were such as to correspond adaptively to almost every
+requirement?--to say nothing of the fact that the production of *more*
+of the protecting substance than is actually necessary could hardly be
+said to be “chemical.”
+
+In fact, we are well entitled to say that we have reached here the very
+heart of life and of biology. If nevertheless we do not call the sum of
+our facts a real proof of vitalism, it is only because we feel unable
+to formulate the analysis of what happens in such a manner as to make
+a machine as the basis of all reactions absolutely unimaginable and
+unthinkable. There *might* be a true machine in the organism producing
+immunity with all its adaptations. We cannot disprove such a doctrine by
+demonstrating that it would lead to a real *absurdity*, as we did in our
+analysis of differentiation of form; there is only a very high degree of
+improbability in our present case. But an indirect *proof* must reduce
+to *absurdity* all the possibilities except one, in order to be a proof.
+
+Mechanistic explanations in all branches of functional physiology
+proper, so much in vogue twenty years ago, can indeed be said to
+have failed all along the line: the only advantage they have brought
+to science is the clearer statement of problems to which we are now
+accustomed. But we are not fully entitled to say[118] that there never
+will be any mechanistic explanation of physiological functions in the
+future. It may seem as improbable as anything can be; but we wish to
+know not what is improbable but what is not possible.
+
+[118] Here again I should like to except from this statement the
+discoveries of Pawlow. See page 204, note 1.
+
+Now of course you might answer me that after we have indeed
+shown that the production of form, as occurring on the basis of
+harmonious-equipotential systems, is a fact that proves vitalism,
+the acts taking place on the basis of that form after its production
+would have been proved to be vitalistic also, or at least to be in
+some connection with vitalistic phenomena. Certainly they would, and
+I myself personally should not hesitate to say so. But that is not
+the question. We have to ask: Is any new proof, *independent of every
+other*, to be obtained from the facts of physiological adaptation in
+themselves? And there is really none. Mere regulatory correspondence
+between stimuli and reactions, even if it be of the adaptive type and
+occur in almost indefinite forms, never really disproves a machine as
+its basis so long as the stimuli and reactions are *simple* and uniform.
+Next summer, however, we shall see that vitalism may be proved by such a
+correspondence if the two corresponding factors are not simple and not
+uniform.
+
+We most clearly see at this point what it really was in our analysis of
+differentiation that allowed us to extract a real proof of vitalism from
+it. Not the mere fact of regulability, but certain specific relations
+of space, of locality, lay at the very foundation of our proof. These
+relations, indeed, and only these relations, made it possible to
+reduce *ad absurdum* any possible existence of a machine as the actual
+basis of what we had studied. In our next chapter again it will be
+space-relations, though analysed in a different manner, that will enable
+us to add a second real proof of vitalism to our first one.
+
+With this chapter we conclude the study of organic regulation in all its
+forms, as far as morphogenesis and metabolism are in question.
+
+But our analysis of these regulations would be incomplete and indeed
+would be open to objections, if we did not devote at least a few words
+to two merely negative topics, which will be taken more fully into
+consideration later on.
+
+
+A FEW REMARKS ON THE LIMITS OF REGULABILITY
+
+There has never been found any sort of “experience” in regulations
+about morphogenesis or in adaptations of the proper physiological
+type. Nothing goes on “better” the second time than it did the first
+time;[119] everything is either complete, whenever it occurs, or it does
+not occur at all.
+
+[119] The few cases of an “improvement” of morphogenetic acts in
+hydroids described by myself are too isolated at present to be more
+than mere problems (*Arch. Entw. Mech.* 5, 1897). The same is true, it
+seems to me, with regard to certain recent discoveries made by R. Pearl
+on *Ceratophyllum* (*Carnegie Inst. Wash. Publ.* No. 58, 1907); and by
+Zeleny on a medusa (*Journ. exp. Zool.* 5, 1907). Pawlow’s discovery,
+that the enzymotic composition of the pancreatic fluid in dogs becomes
+more and more adapted to a specific composition of the food (either meat
+or bread and milk) the longer such a specific composition is offered
+to the individual animal, may probably be understood as a case of mere
+functional adaptation of the cells of the digestive glands, if it stands
+criticism at all (see Bayliss and Starling, *Ergeb. Physiol.* 5, 1906,
+p. 682).
+
+That is the first of our important negative statements about
+regulations; the second relates to the phrase just used, “or it does
+not occur at all.” There are indeed limits of regulability; adaptations
+are not possible to every sort of change of the physiological state:
+sickness and death could not exist if they were; nor is restitution
+possible in all cases where it might be useful. It is a well-known fact,
+that man is only able to heal wounds but is altogether destitute of the
+faculty of regeneration proper. But even lower animals may be without
+this faculty, as are the ctenophores and the nematodes for instance, and
+there is no sort of correspondence between the faculty of restitution
+and the place in the animal kingdom. It is not altogether impossible
+that there may be found, some day, certain conditions under which every
+organism is capable of restoring any missing part; but at present we
+know absolutely nothing about such conditions.[120]
+
+[120] Experiments carried out in the “Biologische Versuchsanstalt” at
+Vienna indeed have shown that many animal types are capable of at least
+a certain degree of restitution, although they had previously been
+denied this faculty by zoologists.
+
+But no amount of negative instances can disprove an existing
+positive--which is what we have been studying. Our analysis based upon
+the existence of regulations is as little disparaged by cases where no
+regulability exists as optical studies are by the fact that they cannot
+be undertaken in absolute darkness.
+
+
+
+
+*D.* INHERITANCE: SECOND PROOF OF THE AUTONOMY OF LIFE
+
+
+All organisms are endowed with the faculty of re-creating their own
+initial form of existence.
+
+In words similar to these Alexander Goette, it seems to me, has given
+the shortest and the best expression of the fact of inheritance. Indeed,
+if the initial form in all its essentials is re-created, it follows from
+the principle of univocality, that, *ceteris paribus*, it will behave
+again as it did when last it existed.
+
+By the fact of inheritance life becomes a rhythmic phenomenon, that is
+to say, a phenomenon, or better, a chain of phenomena, whose single
+links reappear at constant intervals, if the outer conditions are not
+changed.
+
+
+THE MATERIAL CONTINUITY IN INHERITANCE
+
+It was first stated by Gustav Jaeger and afterwards worked out into
+a regular theory by Weismann, that there is a continuity of material
+underlying inheritance. Taken in its literal meaning this statement is
+obviously self-evident, though none the less important on that account.
+For as all life is manifested on bodies, that is on matter, and as the
+development of all offspring starts from parts of the parent bodies,
+that is from the matter or material of the parents, it follows that in
+some sense there is a sort of continuity of material as long as there is
+life--at least in the forms we know of. The theory of the continuity of
+“germ-plasm” therefore would be true, even if germ-cells were produced
+by any and every part of the organism. That, as we know, is not actually
+the case: germ-cells, at least in the higher animals and in plants, are
+produced at certain specific localities of the organism only, and it is
+with regard to this fact that the so-called theory of the “continuity of
+germ-plasm” acquires its narrower and proper sense. There are distinct
+and specific lines of cell-lineage in ontogenesis, so the theory states,
+along which the continuity of germ-protoplasm is kept up, which, in
+other words, lead from one egg to the other, whilst almost all other
+lines of cell-lineage end in “somatic” cells, which are doomed to
+death. What has been stated here is a fact in many cases of descriptive
+embryology, though it can hardly be said to be more than that. We know
+already, from our analytical and experimental study of morphogenesis,
+that Weismann himself had to add a number of subsidiary hypotheses to
+his original theory to account for the mere facts of regeneration proper
+and the so-called vegetative reproduction in plants and in some animals,
+and we have learned that newly discovered facts necessitate still more
+appendixes to the original theory. In spite of that, I regard it as
+very important that the fact of the continuity of some material as one
+of the foundations of inheritance has clearly been stated, even if the
+specialised form of the theory, as advocated by Weismann in the doctrine
+of the “germ-lineages” (“Keimbahnen”) should prove unable to stand
+against the facts.
+
+The important problem now presents itself: What is the material, the
+matter, which is handed down from generation to generation as the
+basis of inheritance? Weismann, as we know, regarded it as a very
+complicated structure, part of which by its disintegration became the
+foundation of individual embryology. We have disproved, on the authority
+of many facts, the latter part of this assumption; but of course the
+first part of it may turn out to be true in spite of this. We have no
+means at present to enable us to say *a priori* anything positive or
+negative about the important question of the nature of that matter, the
+continuity of which in inheritance is in some sense a self-evident fact,
+and we therefore shall postpone the answer until a later point of our
+analytical discussion.
+
+
+ON CERTAIN THEORIES WHICH SEEK TO COMPARE INHERITANCE TO MEMORY
+
+It will be advisable first to study some other theoretical views which
+have been put forward with regard to inheritance. The physiologist
+Hering, as early as 1876, compared all heredity to the well-known fact
+of memory, assuming, so to say, a sort of remembrance of all that
+has happened to the species in the continuity of its generations;
+and several German authors, especially Semon, have lately made this
+hypothesis the basis of more detailed speculation.
+
+It is not clear, either from Hering’s paper[121] or from Semon’s
+book,[122] what is really to be understood here by the word “memory,”
+and, of course, there might be understood by it very different things,
+according to the author’s psychological point of view. If he is a
+“parallelist” with regard to so-called psychical phenomena, he would use
+the word memory only as a sort of collective term to signify a resultant
+effect of many single mechanical events, as far as the material world of
+his parallel system comes into account, with which of course the problem
+of inheritance alone deals; but if he maintains the theory of so-called
+psycho-physical interaction, the psychical would be to him a primary
+factor in nature, and so also would memory. As we have said, it is by no
+means clear in what sense the word “memory” is used by our authors, and
+therefore the *most* important point about the matter in question must
+remain *in dubio*.
+
+[121] *Ueber das Gedächtnis als eine allgemeine Function der organischen
+Materie*, Wien, 1870. New edition in *Klassiker d. exakt. Wiss.*,
+Leipzig, Engelmann.
+
+[122] *Die Mneme*, Leipzig, 1904.
+
+But another topic is even more clear in the theory of inheritance, as
+stated in Hering’s and Semon’s writings. The hypothetical fact that
+so-called “acquired characters” are inherited is undoubtedly the chief
+assumption of that theory. Indeed, it would be difficult to understand
+the advantage of the ambiguous word memory, had it not to call attention
+to the hypothetic fact that the organism possesses the faculty of
+“remembering” what once has happened to it or what it once has “done,”
+so to speak, and profiting by this remembering in the next generation.
+The zoologist Pauly indeed has stated this view of the matter in very
+distinct and clear terms.
+
+As we soon shall have another occasion to deal with the much-discussed
+problem of the “inheritance of acquired characters,” we at present
+need only say a few words about the “memory-theory” as a supposed
+“explanation” of heredity. Undoubtedly this theory postulates, either
+avowedly or by half-unconscious implication, that all the single
+processes in individual morphogenesis are the outcome either of
+adaptations of the morphological type, which happened to be necessary
+in some former generation, or of so-called contingent “variations,” of
+some sort or other, which also happened once in the ancestral line.
+Such a postulate, of course, is identical with what is generally called
+the theory of descent in any of its different forms. This theory is
+to occupy us in the next lectures; at present we only analyse the
+“memory-theory” as a theory of heredity in itself. In any case, to
+regard memory as the leading point in inheritance, at least if it is to
+signify what is called memory in any system of psychology, would be to
+postulate that either adaptation or contingent “variation” has been the
+origin of every morphogenetic process. Indeed, the American physiologist
+Jennings did not hesitate to defend such a view most strongly, and many
+others seem to be inclined to do the same.
+
+But such an assumption most certainly cannot be true.
+
+It cannot be true, because there are many phenomena in morphogenesis,
+notably all the phenomena akin to restitution of form, which occur
+in absolute perfection even the very first time they happen. These
+processes, for the simple reason of their *primary perfection*, cannot
+be due either to “learning” from a single adaptation, or to accidental
+variation. We shall afterwards employ a similar kind of argument to
+refute certain theories of evolution. It therefore may be of a certain
+logical interest to notice that at present, combating the memory-theory
+of inheritance, and hereafter, combating certain theories of descent,
+we select not “adaptation” or “variation” as the central points to be
+refuted, but the assumed *contingency* of both of them.
+
+The word “memory,” therefore, may be applied to the phenomena of
+inheritance only in a very figurative meaning, if at all. We do not
+wholly deny the possibility of an inheritance of acquired characters, as
+will be seen later on, and to such a fact there might perhaps be applied
+such a term as “memory” in its real sense, but we simply *know* that
+there *is* something in inheritance which has no similarity whatever
+to what is called “memory” in any species of psychology. A primary
+perfection of processes occurring quite abnormally proves that there is
+a “knowing” of something--if we may say so--but does not prove at all
+that there is a “remembering.”
+
+
+THE COMPLEX-EQUIPOTENTIAL SYSTEM AND ITS RÔLE IN INHERITANCE[123]
+
+[123] Driesch, *Organ. Regul.* 1901.
+
+But we thus far have reached only negative results. Is the question
+necessarily to remain at this point, which could hardly be said to be
+very satisfying; or could we perhaps get better, that is, positive
+results about inheritance by a change of our analytic methods? Let us
+try to analyse the facts that occur in inheritance instead of beginning
+with hypotheses which claim to be complete explanations. Perhaps we
+shall gain, if but small, yet certainly fixed results by an analysis
+which goes from the facts to the theory and not from the theory to the
+facts.
+
+Let the discussions that are to follow be placed upon a basis as broad
+as possible.
+
+Our studies of morphogenetic restitution have shown us that besides the
+harmonious-equipotential systems another and widely different type of
+morphogenetic “systems” (*i.e.* unities consisting of elements equal in
+morphogenetic faculty) may also be the basis of restitution processes.
+Whilst in the harmonious system the morphogenetic acts performed by
+every single element in any actual case are single acts, the totality
+of all the single acts together forming the harmonious whole, in the
+other type of systems now to be examined, complex acts, that is, acts
+which consist of a manifoldness in space and in time, can be performed
+by each single element, and actually are performed by one or the other
+of them. We therefore have given the title of “complex-equipotential
+systems” to the systems in question, as all our denominations are based
+on the concept of the prospective morphogenetic potency, that is of the
+possible fate of the elements.
+
+The cambium of the Phanerogams may be regarded as the very type of a
+complex-equipotential system, promoting restitution of form. It runs
+through the whole stem of our trees, in the form of a hollow tube,
+placed between the inner and the outer cell-layers of the stem, and
+either branch or root may originate from any single one of its cells,
+just as circumstances require. We might call the cambium a system of the
+“complex” type of course, even if every one of its constituents were
+able to form only a root or only a branch by way of restitution. But in
+fact one and the same element can form both of these complex-structures;
+it depends only on its relative position in the actual part of the stem
+isolated for the purposes of experiment, what will be accomplished in
+every case. Here we have a state of affairs, which we shall encounter
+again when studying regeneration in animals: every element of the system
+may be said to contain potencies for the “ideal whole,” though this
+ideal whole will never be realised in its proper wholeness.[124]
+
+[124] The “ideal whole” is also proved to exist, if any *given*
+“Anlage,” say of a branch, is forced to give origin to a root, as has
+really been observed in certain plants. This case, like many other
+less extreme cases of what might be called “compensatory heterotypy,”
+are best to be understood by the aid of the concept of “prospective
+potency.” It is very misleading to speak of a metamorphosis here. I
+fully agree with Krašan about this question. See also page 112, note 1,
+and my *Organ. Regul.* pp. 77, 78.
+
+But there is no need to recur to the “ideal whole” in many other cases
+of adventitious restitution in plants. On isolated leaves of the
+well-known begonia, a whole plant, containing all the essential parts,
+may arise from any single cell[125] of the epidermis, at least along the
+veins, and in some liverworts it has been shown by Vöchting, that almost
+every cell of the whole is able to reproduce the plant, as is also the
+case in many algae.
+
+[125] Winkler has discovered the important fact, that the adventitious
+buds formed upon leaves may originate either from one single cell of
+the epidermis or from several cells together; a result that is very
+important with respect to the problem of the distribution of “potencies.”
+
+In the animal kingdom it is chiefly and almost solely the phenomena
+of regeneration proper which offer typical instances of our systems,
+since adventitious restitution, though occurring for instance in the
+restitution of the lens of vertebrates from the iris, and though
+connected also with the events in regeneration proper,[126] is of but
+secondary importance in animal restitution, at least, if compared with
+restitution in plants. If we study the regeneration of a leg in the
+common newt, we find that it may take place from every section, the
+point of amputation being quite at our choice. Without regarding here
+the exact order of the regeneration phenomena, which is almost unknown
+at present, we in any case can say without any doubt that the line
+of consecutive possible cross-sections forms a complex-morphogenetic
+system, as every one of them is able to give rise to a complex organ,
+viz. the foot and part of the leg. It is an open question whether this
+complex system is to be called “equipotential” or not. It indeed seems
+to be inequipotential at the first glance, for each single section has
+to form a different organogenetic totality, namely, always that specific
+totality which had been cut off; but if we assume hypothetically that
+the real “Anlage” which is produced immediately by the cells of the
+wounded surface is the very same for all of them, and that it is the
+actual state of organisation which determines to what result this
+Anlage is to lead,[127] we may say that the series of consecutive
+cross-sections of a newt’s leg does form a morphogenetic system of the
+complex-equipotential type, promoting secondary regulations of form.
+
+[126] The “regeneration” of the brain of annelids for instance is far
+better regarded as an adventitious formation than as regeneration
+proper: nothing indeed goes on here at the locality of the wound; a new
+brain is formed out of the ectoderm at a certain distance from it.
+
+[127] A full “analytical theory of regeneration” has been developed
+elsewhere (*Organ. Regul.* p. 44, etc.). I can only mention here that
+many different problems have to be studied by such a theory. The
+formation of the “Anlage” out of the body and the differentiation of
+it into the completely formed results of regeneration are two of them.
+The former embraces the question about the potencies not only of the
+regenerating body but of the elements of the Anlage also; the latter
+has to deal with the specific order of the single acts of regenerative
+processes.
+
+Now all these difficulties vanish, if we consider the regeneration of
+animals, such for instance as many worms of the annelid class or our
+familiar ascidian *Clavellina*, in which regeneration in both directions
+is possible. The wound at the posterior end of the one half which
+results from the operation forms a posterior body half, the wound at
+the anterior end of the other half forms an anterior one. Again, it is
+the ideal whole which we meet here: each section of the body indeed may
+be said to contain the potencies for the production of the totality,
+though actually this totality is always realised by the addition of two
+partial organisations. The title of complex-equipotential systems thus
+seems to be fully justified as applied to the systems which are the
+basis of regeneration: each section of the regenerating body may in fact
+produce the same complex whole, or may, if we prefer to say so, at least
+prepare the ground for that complex Anlage, out of which the complex
+totality is actually to arise, in the same manner.
+
+It often occurs in science, that in rather strange and abnormal
+conditions something becomes apparent which might have been found
+everywhere, which is lying before our eyes quite obviously. Are
+we not in just such a condition at present? In order to study the
+complex-equipotential systems, we turn to the phenomena of regeneration
+and of restitution in general; we occasionally even introduce hypotheses
+to render our materials more convenient for our purposes; and all the
+time there is one sort of complex-equipotential system in the body of
+every living being, which only needs to be mentioned in order to be
+understood as such, and which indeed requires no kind of preliminary
+discussion. The system of the propagation cells, in other words the
+sexual organ, is the clearest type of a complex-equipotential system
+which exists. Take the ovary of our sea-urchin for instance, and there
+you have a morphogenetic system every element of which is equally
+capable of performing the same complex morphogenetic course--the
+production of the whole individual.
+
+Further on we shall deal exclusively with this variety of our systems,
+and in doing so we shall be brought back to our problem of heredity. But
+it had its uses to place our concept of the complex-equipotential system
+upon such a broad basis: we at once gave a large range of validity to
+all that is to follow--which, indeed, does not apply to inheritance
+alone, though its significance in a theory of heredity may be called its
+most important consequence.
+
+
+THE SECOND PROOF OF LIFE-AUTONOMY. ENTELECHY AT THE BOTTOM OF INHERITANCE
+
+After we had established the concept of the harmonious-equipotential
+system in a former chapter, we went on to study the phenomena of the
+differentiation of it, and in particular the problem of the localisation
+of all differentiations. Our new concept of the complex-equipotential
+system is to lead us to an analysis of a different kind: we shall pay
+special attention to the origin, to the *genesis* of our complex systems
+that show equipotentiality.
+
+If we review the process of ontogenesis, we are able to trace back every
+complex system to a very small group of cells, and this small group of
+cells again to one single cell. So in plants the cambium may be shown
+to have originated in a sort of tissue-rudiment, established at a very
+early period, and the ovary may be demonstrated to be the outcome of a
+group of but a few cells, constituting the first visible “Anlage” of the
+reproductive organs. At the end then, or from another point of view at
+the beginning, a single cellular element represents the very primordial
+egg-cell.
+
+The whole cambium, there can be no doubt, must be regarded as the result
+of a consecutive number of cell-divisions of the one cell from which it
+originates. So must it be with the ovary. The primordial egg-cell has
+undergone a long line of consecutive divisions; the single eggs are the
+last result of them.
+
+We now proceed to some considerations which have a certain
+logical similarity to those which inaugurated our analysis of the
+differentiation of the harmonious-equipotential systems, though the
+facts in question are very different.
+
+Viewed by itself without any kind of prepossessions, as it might
+be by any one who faces a new problem with the single postulate of
+introducing new natural entities--to use the scholastic phrase--as
+little as possible, the development of the single egg might be regarded
+as proceeding on the foundation of a very complicated sort of machine,
+exhibiting a different kind of construction in the three chief
+dimensions of space, as does also the organism which is to be its result.
+
+But could such a theory--irrespective of all the experimental facts
+which contradict it--could such a theory stand before the *one* fact,
+that there occurs a *genesis* of that complex-equipotential system,
+of which our one single egg forms a part? Can you imagine a very
+complicated machine, differing in the three dimensions of space, to
+be divided hundreds and hundreds of times and in spite of that to
+remain always the same whole? You may reply that during the period
+of cell-divisions there is still no machine, that the machine is
+established only after all the divisions are complete. Good; but what
+then constructs this machine in the definitive cells of our systems, say
+in the eggs? Another sort of machine perhaps? That could hardly be said
+to be of much use. Or that entelechy of which we have spoken? Then you
+would recur to our first proof of vitalism and would burden entelechy
+with a specific performance, that is with the construction of the
+hypothetic machine which you are postulating in every single egg. But of
+course you would break the bounds of physics and chemistry even then.
+
+It seems to me that it is more simple, and so to say more natural, not
+to recur to our first proof of life-autonomy in order to keep to the
+“machine theory” in this new branch of inquiry, but to consider facts as
+they offer themselves to analysis.
+
+But then indeed we are entitled to draw an independent second proof of
+the autonomy of life from our analysis of the genesis of systems of the
+complex-equipotential type. We say it is a mere absurdity to assume that
+a complicated machine, typically different in the three dimensions of
+space, could be divided many many times, and in spite of that always
+be the whole: therefore there cannot exist any sort of machine as the
+starting-point and basis of development.
+
+Let us again apply the name entelechy to that which lies at the very
+beginning of all individual morphogenesis.
+
+Entelechy thus proves to be also that which may be said to lie at
+the very root of inheritance,[128] or at least of the outcome of
+inheritance; the individual formation of the next generation is shown
+not to be performed by a machine but by a natural agent *per se*.
+
+[128] And, of course, at the root of every new starting of certain
+parts of morphogenesis also, as in regeneration and in adventitious
+budding; these processes, as we know, being also founded upon
+“complex-equipotential systems,” which have had their “genesis.”
+
+
+THE SIGNIFICANCE OF THE MATERIAL CONTINUITY IN INHERITANCE
+
+But what about the material continuity appearing in inheritance, which
+we have said to be almost self-evident, as life is only known to exist
+on material bodies? Is there not, in fact, a serious contradiction
+in admitting at the same time entelechy on the one side and a sort
+of material condition on the other as the basis of all that leads to
+and from inheritance? Next summer the relation between matter and our
+autonomous agent of life will be studied more fully; at present it must
+be enough to state in a more simple and realistic way, what we hold
+this relation to be. There is no contradiction at all in stating that
+material continuity is the basis of inheritance on the one side, and
+entelechy on the other. It would be very inconvenient for us if there
+were any: for the material continuity is a mere fact and our entelechy
+we hope we have proved to exist also; if now there were any sort of
+contradiction in assuming the existence of both of them, of course it
+would be fatal to our proof.
+
+Let us try to comprehend what is meant by the statement that entelechy
+and something material are at work in inheritance at the same time.
+Entelechy has ruled the individual morphogenesis of the generation which
+is regarded as being the starting-point for inheritance, and will rule
+also the morphogenesis of the generation which is to follow; entelechy
+determines the egg to be what it is, and the morphogenesis starting from
+this egg to be what it is also. Entelechy, at present, is not much more
+for us than a mere word, to signify the autonomous, the irreducible of
+all that happens in morphogenesis with respect to *order*, in the one
+generation and in the next. But may not the material continuity which
+exists in inheritance account perhaps for the material elements *which
+are to be ordered*? In such a way, indeed, I hope we shall be able to
+reconcile entelechy and the material basis of heredity. May it not be
+that there exist some “means” for morphogenesis, which are handed down
+from generation to generation, always controlled by entelechy, and which
+constitute the real significance of the continuity of matter during
+inheritance?
+
+
+THE EXPERIMENTAL FACTS ABOUT INHERITANCE
+
+Discoveries of the last few years do seem to show that such means
+of a material character, though not the foundation of that order of
+processes which is inherited, are nevertheless among the most necessary
+conditions for the accomplishment of inheritance in general. It is
+scarcely necessary to remind you that for very many years all concrete
+research on heredity proper--that is, the actual comparison of the
+various specific characters in the generations of the grandfather, the
+father, and the child--was due to Galton. You may also be aware that in
+spite of Galton’s inestimable services it was not till 1900 that one of
+the active principles concerned in inheritance was found independently
+by de Vries, Correns, and Tschermak, and that this principle happened
+to be one that *had* been discovered already, stated with the utmost
+clearness and precision by the Augustinian monk, Gregor Mendel,[129] as
+early as 1865, though it had been completely forgotten ever since.
+
+[129] New edition in the “Klassiker d. exakt. Wiss.” Leipzig, Engelmann;
+see also Bateson, *Mendel’s Principles of Heredity*, Cambridge, 1902.
+
+The so-called “rule of Mendel” is based upon experiments with hybrids,
+that is, with the offspring of parents belonging to different species,
+or, at least, varieties, but it relates not to the characters of the
+generation resulting immediately from hybridisation, the “first”
+generation of hybrids, as we shall call it, but to the characters of
+that generation which is the result of crossing the hybrids with each
+other, provided that this leads to any offspring at all. There are many
+cases indeed, both amongst animals and plants, where the offspring of
+the hybrids, or in other terms the “second” generation, is found to
+consist of individuals of three different types--the mixed[130] type
+of the hybrids themselves, and the two pure types of the grandparents.
+Whenever the individuals of the “second” generation are separated into
+these three different types, hybrids are said to “split.” It is the
+fact of this splitting on the one hand, and on the other hand a certain
+statement about the numbers of individuals in the three different types
+of the “second” generation, that gives its real importance to Mendel’s
+rule.
+
+[130] For the sake of simplicity I shall not deal here with those
+cases of hybridisation in which one quality is “recessive,” the other
+“dominant,” but only allude to the cases, less numerous though they be,
+where a real mixture of maternal and paternal qualities occurs.
+
+Before discussing what may follow from Mendel’s discovery for the
+theory of heredity, we must lay stress on the fact that there are many
+exceptions to his rule. In quite a number of cases the hybrids are of
+one or more types, which remain constant: there is no splitting at all
+in the second generation. But that does not affect the rule of Mendel in
+those cases where it is true. Where there is a “splitting” in the second
+generation, there also are the numerical proportions stated by Mendel;
+there never are other relations among the numbers of individuals of the
+mixed and of the two pure types than those given by his rule. I regard
+it as very important that this real meaning of Mendel’s principle should
+be most clearly understood.
+
+From the fact of the splitting of hybrids in the second generation most
+important consequences may be drawn for the theory of inheritance; the
+split individuals, if crossed with each other, always give an offspring
+which remains pure; there is no further splitting and no other change
+whatever. The germ-cells produced by the split individuals of the second
+generation may therefore be said to be “pure,” as pure as were those of
+the grandparents. But that is as much as to say that the pureness of
+the germ-cells has been preserved in spite of their passing through the
+“impure” generation of the hybrids, and from this fact it follows again
+that the union of characters in the hybrids must have been such as to
+permit pure separation: in fact, the germ-cells produced by Mendelian
+hybrids may hypothetically be regarded as being pure themselves.[131]
+
+[131] This hypothesis was first suggested by Sutton and is at present
+held by orthodox Mendelians; but probably things are a little more
+complicated in reality, as seems to be shown by some facts in the
+behaviour of so-called “extracted recessives.” In Morgan’s *Experimental
+Zoology*, New York, 1907, a full account of the whole matter is given.
+
+We have not yet considered one feature of all experiments in
+hybridisation, which indeed seems to be the most important of all for
+the theory of inheritance, if taken together with the fact of the
+pureness of the germs. The rule of Mendel always relates to one single
+character of the species or varieties concerned in hybridisation, and
+if it deals with more than one character, it regards every one of them
+separately; indeed, the rule holds for every one of them irrespective
+of the others. We cannot study here how this most important fact of
+the independence of the single characters of a species with regard to
+inheritance leads to the production of new races, by an abnormal mixture
+of those characters. We only take advantage of the fact theoretically,
+and in doing so, I believe, we can hardly escape the conclusion that
+the independence of the single characters in inheritance, taken
+together with the pureness of the germ-cells in the most simple form
+of hybrids, proves that there occurs in inheritance a sort of handing
+over of single and separate morphogenetic agents which relate to the
+single morphogenetic characters of the adult. We may use Bateson’s
+word “allelomorphs” for these agents, or units, as they may be called,
+thereby giving expression to the fact that the single and separate
+units, which are handed over in inheritance, correspond to each other in
+nearly related species without being the same.
+
+And so we have at least an inkling of what the material continuity of
+inheritance is to mean, though, of course, our “single and separate
+morphogenetic agents,” or “units” or “allelomorphs” are in themselves
+not much more than unknown somethings described by a word; but even then
+they are “somethings.”
+
+Besides the researches relating to the rule of Mendel and its
+exceptions, founded, that is, upon a study of the “second” generation of
+hybrids, there is another important line of research lately inaugurated
+by Herbst, which investigates the first generation in hybridisation.
+The hybrids themselves are studied with the special purpose of finding
+out whether the type of the single hybrid may change according to the
+conditions of its development, both outer and inner. The discoveries
+thus made may lead some day to a better understanding of the intimate
+nature of the “units” concerned in heredity, and perhaps to some
+knowledge of the arranging and ruling factor in morphogenesis also.
+
+Starting from the discovery of Vernon, that the hybrids of sea-urchins
+are of different types according to the season, Herbst[132] was able
+to show that differences among the hybrids with regard to their being
+more of the paternal or more of the maternal type, are in part certainly
+due to differences in temperature. But there proved to be still another
+factor at work, and Herbst has succeeded in discovering this factor by
+changing the internal conditions of morphogenesis. Whenever he forced
+the eggs of *Sphaerechinus* to enter into the first[133] phase of
+artificial parthenogenesis and then fertilised them with the sperm of
+*Echinus*, he was able to approximate the offspring almost completely
+to the maternal type, whilst under ordinary conditions the hybrids in
+question follow the paternal far more than the maternal organisation.
+
+[132] *Arch. Entw. Mech.* 21, 22, and 24, 1906-7; see also Doncaster,
+*Phil. Trans. Royal Soc.* London, B. 196, 1903. The influence of
+different temperature upon the organisation of the hybrids is not
+always quite pure, inasmuch as the paternal and the maternal forms may
+themselves be changed by this agent. In spite of that there exists an
+influence of the temperature upon the hybrid *as such*, at least with
+regard to certain features of its organisation.
+
+[133] Only the nucleus of the egg had entered its first stages of
+activity.
+
+What is shown, in the first place, by these discoveries is the
+importance of an arranging and ruling factor in spite of all units. The
+organism is always one *whole* whether the paternal properties prevail
+or the more complicated maternal ones; in other words, all so-called
+properties that consist in the *spatial relations of parts* have nothing
+to do with “units” or “allelomorphs,” which indeed cannot be more
+than necessary means or materials, requiring to be ordered. As to the
+character of the morphogenetic single and separate units themselves
+Herbst is inclined to regard them as specific chemical substances which
+unite correspondingly during nuclear conjugation, forming a sort of
+loose chemical compound. It would depend on the constitution of this
+compound whether germ-cells of hybrids could become pure or not.
+
+
+THE RÔLE OF THE NUCLEUS IN INHERITANCE
+
+At the end of our studies on heredity we hardly can avoid saying a
+few words about the problem of the localisation of the morphogenetic
+units in the germ-cells themselves. Is it in the protoplasm or in the
+nucleus that they are placed? You all know that this question was for
+a long time regarded as more important than any other, and perhaps
+you have already blamed me for not raising it until now. But in my
+opinion results gained by the purely analytical method and carefully
+established, are always superior to those which are of a merely
+descriptive nature and doubtful besides. The famous problem of the part
+played by the nucleus in inheritance is both descriptive and doubtful:
+it is only, so to say, of factual, not of analytical importance, and
+quite insoluble at present.
+
+As for our second proof of vitalism, stating that no kind of machine
+inside the germ-cells can possibly be the foundation of their
+morphogenesis, it is clear that the protoplasm and the nucleus may both
+come into account here on equal terms. If you prefer to say so, it is to
+the nucleus and to its division in particular that the second proof of
+autonomy relates, while the first, though not over-looking the presence
+of nuclei,[134] deals “especially” with the protoplasmic nature of its
+“systems.”
+
+[134] The first proof of vitalism, indeed, rests upon the analysis of
+the differentiation of an harmonious-equipotential system as a *whole*:
+this *whole* cannot be a machine that would relate to differentiation as
+a *whole*; the question whether there might be any machines distributed
+*in* the whole, in the form of the nuclei is of no importance at all in
+this argument. Moreover the pressure experiments (see page 63) prove the
+unimportance of such “machines” for the specificity of differentiation,
+and the second proof of vitalism shows that the nuclei cannot be
+regarded as machines accounting for differentiation in *any* way.
+
+What then can we say, on the basis of actual facts, about the part taken
+by the protoplasm and by the nucleus in inheritance, now that we have
+learnt from our analytical discussion that both of them cannot be any
+kind of morphogenetic machine, but can only be means of morphogenesis?
+Let us state our question in the following way: whereabouts in the
+germ-cells are those “means” of morphogenesis localised, the existence
+of which we infer from the material continuity in the course of
+generations in general and from the facts discovered about hybridisation
+in particular?
+
+The first of the facts generally said to support the view that the
+nucleus of the germ-cells exerts a specified influence upon the
+processes of development and inheritance, relates to the proportion
+between protoplasm and nuclear material in the egg and in the spermiae.
+This proportion is very different in the two sexual products, as we
+know, there being an enormous preponderance of the protoplasm in the
+egg, of the nucleus in the spermatozoon. This seems to indicate that
+the proportion between protoplasm and nucleus is fairly indifferent
+for inheritance, as all the facts go to show that inheritance from
+the father is as common as inheritance from the mother. It is in the
+nucleus, and in the nucleus alone, that any similarity of organisation
+exists between the two sexual products, so very different in all other
+respects: therefore the nucleus should be the organ of inheritance. The
+phenomena of nuclear division, of karyokinesis, which are quite equal in
+both sexual cells, are certainly well fitted to support this hypothesis.
+
+There seems indeed to be some truth in this reasoning, but nevertheless
+it must remain hypothetical; and it must never be forgotten that
+there may be very probably some sort of morphogenetic importance in
+protoplasm also. Rauber and afterwards Boveri[135] have tried to prove
+experimentally that it is on the nuclear chromatic substance only that
+inheritance depends, but the first of these authors failed to get any
+results at all, and the latter obtained only ambiguous ones. Godlewski,
+on the contrary, has fertilised purely protoplasmic egg-fragments of
+the sea-urchin with the sperm of quite another group of Echinoderms,
+and obtained in spite of that a few stages of development of the
+pure maternal type. This experiment seems to place the morphogenetic
+importance of protoplasm beyond all doubt.
+
+[135] Boveri tried to fertilise enucleated fragments of the egg of
+*Sphaerechinus* with the sperm of *Echinus*. He failed to get any
+results in isolated experiments, but found a few small larvae of the
+pure *Echinus* type in large cultures consisting of shaken eggs. But
+later experiments on hybridisation in sea-urchins have shown that a full
+hybrid of *Echinus* and *Sphaerechinus* may be purely paternal also.
+
+I should prefer not to make any definite statement about our problem at
+present. Our actual knowledge of the organisation and metabolism of both
+nucleus and protoplasm is so extremely small and may relate to such very
+insignificant topics, that any definite decision is impossible. I myself
+believe that the nucleus plays an important part in heredity, perhaps
+even a greater one than protoplasm, but this is only my belief.[136]
+
+[136] Surely the new results of Herbst, mentioned above, are another
+indication of the importance of something in the nucleus. The first
+stage in parthenogenesis, which he used in his experiments, is a nuclear
+phenomenon.
+
+The discovery of Gruber and others, that Protozoa are only capable of
+restitution if they contain at least a fragment of the nucleus, has
+also been used occasionally as a proof of the morphogenetic importance
+of the nucleus. But might not this absence of restitution where nuclear
+material is lacking be understood equally well on the hypothesis of Loeb
+and R. S. Lillie that the nucleus is a centre of oxidation in the cell?
+Remove the heart from a vertebrate and the animal will not digest any
+more; but in spite of that the heart is not the organ of digestion.
+
+And so we lay stress once more upon this point: that the experimental
+results of hybridisation and the analytical results obtained by the
+discussion of the complex-equipotential systems are of greater value
+to the theory of heredity than all speculation about the importance or
+unimportance of special constituents of the cell, of whose organisation,
+chemistry, and physics, scarcely anything is known at present.[137]
+
+[137] Boveri (*Ergebn. üb. d. Konstitution etc. des Zellkerns*, Jena,
+1904; and “Zellen-Studien VI.” *Jen. Zeitschr.* 43, 1907) has made it
+highly probable by experiments that the different chromosomes of the
+nucleus of the sexual products play a different part in morphogenesis,
+though not in the sense of different single representatives of
+different single organs. This doctrine, of course, would not alter
+the whole problem very much: the chromosomes would only be *means* of
+morphogenesis and nothing else, no matter whether they were of equal or
+of different formative value. It only is with regard to the problem of
+the determination of sex (see page 107, note 3), that the morphogenetic
+singularity of *one* certain specific chromosome can be said to be
+proved.
+
+
+VARIATION AND MUTATION
+
+Heredity, it has been said, may be understood as resting upon the fact
+that each organism forms its own initial stage again, and that this
+initial stage always encounters conditions of the same kind.
+
+If this statement were quite correct, all the individuals of a given
+species would be absolutely alike everywhere and for ever. But they
+are not alike; and that they are not alike everywhere and for ever is
+not merely the only real foundation of the so-called theory of descent
+we possess, but also forces us to change a little our definition of
+heredity, which now proves to have been only a sort of approximation to
+the truth, convenient for analytical discussion.
+
+In the first place, the conditions which surround the initial stages
+of morphogenesis are not quite equal in every respect: and indeed
+the offspring of a given pair of parents, or better, to exclude all
+complications resulting from sexual reproduction, or amphimixis, as
+Weismann called it--the offspring of one given parthenogenetic female
+are not all equal among themselves. The individuals of each generation
+are well known to vary, and it is especially in this country that the
+so-called individual or fluctuating variation has been most carefully
+studied by statistical methods, Galton and Weldon being the well-known
+pioneers in this field.[138] In fact, if we are allowed to assume that
+this sort of variation is the outcome of a variation of conditions--in
+the most general meaning of the word--we only follow the opinion
+which has almost universally been adopted by the biologists[139] that
+are working at this branch of the subject. Variation proper is now
+generally allowed to be the consequence of variations in nutrition;
+the contingencies of the latter result in contingencies of the former,
+and the law of contingencies is the same for both, being the most
+general law of probability. Of course under such an aspect fluctuating
+variation could hardly be called an exception, but rather an addition to
+inheritance.
+
+[138] H. M. Vernon, *Variations in Animals and Plants*, London, 1903.
+
+[139] De Vries, *Die Mutationstheorie*, i., 1901; and Klebs, *Jahrb.
+wiss. Bot.* 42, 1905.
+
+But there are other restrictions of our definition of heredity. The
+initial stage which is formed again by an organism is not always quite
+identical in itself with the initial stage of its own parent: Bateson
+and de Vries were the first to study in a systematic way these real
+exceptions[140] to true inheritance. As you know, de Vries has given
+them the name of “mutations.” What is actually known on this subject is
+not much at present, but nevertheless is of great theoretical value,
+being the only real foundation of all theories of descent, as we shall
+see in the next lectures. “Mutations” are known to exist at present only
+among some domesticated animals and plants. Nothing of a more general
+character can be said about their law or meaning.[141]
+
+[140] They would not be “real exceptions” if Klebs (*Arch. Entw. Mech.*
+24, 1907) were right in saying that both variations and mutations owe
+their existence to external agents. What is really *proved* by Klebs
+is the possibility of changing the *type* of a curve of variation and
+of provoking certain discontinuous varieties by external means. See
+also Blaringhem (*Comptes rend.* 1905-6, and *Soc. de Biol.* 59, 1905),
+and MacDougal (*Rep. Depart. Bot. Res., 5th Year-book Carnegie Inst.*,
+Washington, 129).
+
+[141] H. de Vries, *Species and Varieties: their Origin by Mutation*,
+London, 1905. A short review of the “mutation-theory” is given by Francé
+in *Zeitschrift f. d. Ausbau d. Entwickelungslehre*, i. 1907. It is well
+known that Gautier, and, in the first place, Korshinsky, advocated a
+similar view previous to the authors named in the text.
+
+
+
+
+CONCLUSIONS FROM THE FIRST MAIN PART OF THESE LECTURES
+
+
+In finishing our chapter on inheritance, we at the same time have
+finished the first main part of our lectures; that part of them which
+has been devoted exclusively to the study of the morphogenesis of the
+*individual*, including the functioning of the adult individual form.
+We now turn to our second part, which is to deal with the problems of
+the diversities of individual forms, with morphological systematics. The
+end of our chapter on inheritance has already led us to the threshold of
+this branch of biological science.
+
+The chief result of the first main part of our lectures has been to
+prove that an autonomy of life phenomena exists at least in some
+departments of individual morphogenesis, and probably in all of them;
+the real starting-point of all morphogenesis cannot be regarded as a
+machine, nor can the real process of differentiation, in all cases where
+it is based upon systems of the harmonious equipotential type. There
+cannot be any sort of machine in the cell from which the individual
+originates, because this cell, including both its protoplasm and its
+nucleus, has undergone a long series of divisions, all resulting in
+equal products, and because a machine cannot be divided and in spite of
+that remain what it was. There cannot be, on the other hand, any sort
+of machine as the real foundation of the whole of an harmonious system,
+including many cells and many nuclei, because the development of this
+system goes on normally, even if its parts are rearranged or partly
+removed, and because a machine would never remain what it had been in
+such cases.
+
+If our analytical discussions have thus led us to establish a typical
+kind of vitalism, it follows that we can by no means agree with Wilhelm
+Roux in his denomination of the analytical science of the individual
+form and form-production as “Entwickelungsmechanik,” “developmental
+mechanics,” a title, which, of course, might easily be transformed
+into that of “morphogenetic mechanics,” to embrace not only normal
+development, but restitution and adaptation too. We feel unable to speak
+of “mechanics” where just the contrary of mechanics, in the proper
+meaning of the word, has been proved to exist.
+
+Names of course are of comparatively small importance, but they
+should never be allowed to be directly misleading, as indeed the term
+“Entwickelungsmechanik” has already proved to be. Let us rather say,
+therefore, that we have finished with this lecture that part of our
+studies in biology which has had to deal with morphogenetic physiology
+or physiological morphogenesis.
+
+Once more we repeat, at this resting-point in our discussions, that both
+of our proofs of life-autonomy have been based upon a careful analysis
+of certain facts about the distribution of morphogenetic potencies in
+two classes of morphogenetic systems, and upon nothing else. To recall
+only one point, we have not said that regeneration, merely because it
+is a kind of restitution of the disturbed whole, compels us to admit
+that biological events happen in a specific and elemental manner, but,
+indeed, regeneration *does* prove vitalism, because it is founded upon
+the existence of certain complex-equipotential systems, the analysis of
+the genesis of which leads to the understanding of life-autonomy. This
+distinction, in fact, is of the greatest logical importance.
+
+
+
+
+PART II
+
+SYSTEMATICS AND HISTORY
+
+*A.* THE PRINCIPLES OF SYSTEMATICS
+
+
+RATIONAL SYSTEMATICS
+
+All systematics which deserves the predicate “rational” is founded
+upon a concept or upon a proposition, by the aid of which a totality
+of specific diversities may be understood. That is to say: every
+system claiming to be rational gives us a clue by which we are able to
+apprehend either that there cannot exist more than a certain number of
+diversities of a certain nature, or that there can be an indefinite
+number of them which follow a certain law with regard to the character
+of their differences.
+
+Solid geometry, which states that only five regular bodies are possible,
+and points out the geometrical nature of these bodies, is a model
+of what a rational system should be. The theory of conic sections
+is another. Take the general equation of the second degree with two
+unknowns, and study all the possible forms it can assume by a variation
+of its constants, and you will understand that only four different types
+of conic sections are possible--the circle, the ellipse, the hyperbola,
+and the parabola.
+
+In physics and chemistry no perfect rational systems have been
+established hitherto, but there are many systems approaching the ideal
+type in different departments of these sciences. The chemical type of
+the monohydric saturated alcohols, for instance, is given by the formula
+C_nH_{2n+1}OH, and in this formula we not only have an expression of
+the law of composition which all possible alcohols are to follow,--but,
+since we know empirically the law of quantitative relation between
+*n* and various physical properties, we also possess in our formula a
+general statement with respect to the totality of the properties of any
+primary alcohol that may be discovered or prepared in the future. But
+chemistry has still higher aims with regard to its systematics: all of
+you know that the so-called “periodic law of the elements” was the first
+step towards a principle that may some day give account of the relation
+of all the physical and chemical properties of any so-called element
+with its most important constant, the atomic weight, and it seems to be
+reserved for the present time to form a real fundamental system of the
+“elements” on the basis of the periodic law by the aid of the theory
+of electrons. Such a fundamental system of the elements would teach us
+that there can only be so many elements and no more, and only of such a
+kind. In crystallography a similar end has been reached already by means
+of certain hypothetic assumptions, and systematics has here accounted
+for the limited number and fixed character of the possible forms of
+crystalline symmetry.
+
+It is not difficult to understand the general logical type of all
+rational systems, and logic indeed can discover it without appealing
+to concrete sciences or to geometry. Rational systematics is always
+possible whenever there exists any fundamental concept or proposition
+which carries with it a principle of division; or to express it somewhat
+differently, which would lead to contradictions, if division were to
+be tried in any but one particular manner. The so-called “genus,” as
+will easily be perceived, then embraces all its “species” in such a
+manner that all peculiarities of the species are represented already in
+properties of the genus, only in a more general form, in a form which
+is still unspecified. The genus is both richer in content and richer in
+extent than are the species, though it must be added that its richness
+in content is, as it were, only latent: but it may come into actuality
+by itself and without any help from without.
+
+We are dealing here with some of the most remarkable properties of the
+so-called synthetic judgments *a priori* in the sense of Kant, and,
+indeed, it seems that rational systematics will only be possible where
+some concept of the categorical class or some proposition based upon
+such concept lies at the root of the matter or at least is connected
+with it in some way. In fact, all rational systems with regard to the
+relations of symmetry in natural bodies deal ultimately with space; or
+better, all systems in such fields are able to become rational only if
+they happen to turn into questions of spatial symmetry.
+
+All other genera and species, whether of natural bodies or of facts,
+can be related only on the basis of empirical abstraction, *i.e.* can
+never attain rationality: here, indeed, the genus is richer in extent
+and poorer in content than are the species. The genus is transformed
+into the species, not by any inherent development of latent properties,
+but by a mere process of addition of characteristic points. It is
+impossible to deduce the number or law or specifications of the species
+from the genus. Mere “classification,” if we may reserve the honorable
+name of systematics for the rational type, is possible here, a mere
+statement in the form of a catalogue, useful for orientation but for
+nothing more. We may classify all varieties of hats or of tables in the
+same way.
+
+
+BIOLOGICAL SYSTEMATICS
+
+At this point we return from our logical excursion to our proper subject
+of biology; for I am sorry to say biological systematics is at present
+of our second type of systematics throughout: it is classification pure
+and simple. We have a catalogue in our hands, but nothing more.
+
+Such a statement of fact conveys not a particle of censure, casts not
+the least reflection on the gifted men who created the classification of
+animals or plants. It is absolutely necessary to have such a catalogue,
+and indeed the catalogue of the organisms can be said to have been
+improved enormously during the advance of empirical and descriptive
+biological science. Any classification improves as it becomes more
+“natural,” as the different possible schemes of arrangement, the
+different reasons of division, agree better and better in their results;
+and, in fact, there has been a great advance of organic classification
+in this direction. The “natural” system has reached such perfection,
+that what is related from one point of view seems nearly related also
+from almost all points of view which are applicable, at least from those
+which touch the most important characteristics. There has been a real
+weighing of all the possible reasons of division, and that has led to a
+result which seems to be to some extent final.
+
+But, nevertheless, we do not understand the *raison d’être* of the
+system of organisms; we are not at all able to say that there must be
+these classes or orders or families and no others, and that they must be
+such as they are.
+
+Shall we ever be able to understand that? Or will organic systematics
+always remain empirical classification? We cannot answer this question.
+If we could, indeed, we should have what we desire! As simple relations
+of space are certainly not the central point of any problematic rational
+organic systematics even of the future, the question arises, whether
+there could be found any principle of another type in the realm of
+synthetic *a priori* judgments which could allow an inherent sort of
+evolution of latent diversities, as do all judgments about spatial
+symmetry. At the end of the second course of these lectures, which is to
+be delivered next summer, we shall be able to say a few more words about
+this important point.
+
+The concept of what is called “a type,” due almost wholly to Cuvier and
+Goethe, is the most important of all that classification has given to
+us. Hardly second in importance is the discovery of the “correlation of
+parts,” as a sort of connection which has the character of necessity
+without being immediately based upon causality. Rádl seems to be
+the only modern author who has laid some stress on this topic. The
+harmony which we have discovered in development is also part of this
+correlation. When, later on, we come to discuss analytically our well
+established entelechy as the ultimate basis of individual organisation,
+we shall be able to gain more satisfactory ideas with respect to the
+meaning of the non-causal but necessary connection, embraced in the
+concepts of type and of correlation of parts.
+
+The type is a sort of irreducible arrangement of different parts; the
+correlation deals with the degree and the quality of what may be called
+the actual make of the parts, in relation to one another: all ruminants,
+for instance, are cloven-footed, the so-called dental formulae are
+characteristic of whole groups of mammals. Of course all such statements
+are empirical and have their limits: but it is important that they are
+possible.[142]
+
+[142] Recent years have created the beginnings of a systematics based on
+chemical differences of metabolism and its products: such differences in
+fact have been found to go hand in hand with diversities of the type in
+some cases (v. Bunge, Przibram, etc.).
+
+It has been the chief result of comparative embryology to show that the
+type as such is more clearly expressed in developmental stages than
+it is in the adults, and that therefore the embryological stages of
+different groups may be very much more similar to each other than are
+the adults: that is the truth contained in the so-called “biogenetisches
+Grundgesetz.” But the specific differences of the species are not
+wanting in any case of ontogeny, in spite of such similarities in
+different groups during development.
+
+We have applied the name “systematics” or, if rationality is excluded,
+“classification” to all that part of a science which deals with
+diversities instead of generalities: in such a wide meaning systematics,
+of course, is not to be confused with that which is commonly called so
+in biology, and which describes only the exterior differences of form.
+Our systematics is one of the two chief parts of biology; what are
+called comparative anatomy and comparative embryology are its methods.
+For it must be well understood that these branches of research are only
+methods and are not sciences by themselves.
+
+
+
+
+*B.* THE THEORY OF DESCENT
+
+
+1. GENERALITIES
+
+It is most generally conceded at the present time that the actually
+existing state of all organisms whatsoever is the result of their
+history. What does that mean? What are the foundations upon which the
+assumption rests? What is the relation of systematics to history? In
+raising such questions and considerations we are treading the ground
+sacred to the theory of descent.
+
+I well know that you prefer the name “theory of evolution” for what
+I am speaking of: but it may be misleading in various respects. We
+already know that quite a determinate meaning has been given to the word
+“evolutio” as applied to individual morphogenesis, “evolutio” being
+here opposed to “epigenesis.” Now there would be nothing against the
+use of the word evolution in a wider sense--indeed it is often applied
+nowadays to denote the fact that a something is actually “evolved” in
+embryology--if only our entelechy had taken the place of the machine
+of the mechanists. But that is the very point: there must be a real
+“evolving” of a something, in order that the word evolution may be
+justified verbally: and that is not the case in so-called phylogeny. At
+least we know nothing of an evolutionary character in the problematic
+pedigree of the organisms, as we shall see more fully hereafter. The
+term “theory of descent” is therefore less open to objection than is the
+usual English term. The word transformism, as used by the French, would
+also be a very good title.
+
+The theory of descent is the hypothetic statement that the organisms
+are really allied by blood among each other, in spite of their
+diversities.[143] The question about their so-called monophyletic
+or polyphyletic origin is of secondary importance compared with the
+statement of relationship in general.
+
+[143] We prefer this unpretending definition of the theory of descent
+to every other. As soon as one introduces into the definition the
+concept of the “transmutability of species,” the term “species” would
+require a special definition, and that would lead to difficulties which
+it is unnecessary to deal with for our main purposes. It has been
+remarked by Krašan, (*Ausichten und Gespräche über die individuelle und
+specifische Gestaltung in der Natur*) and by several other writers,
+that the problem of mutability or immutability of course relates to the
+individuals in the first place. I should like to add to this remark that
+the possibility must be admitted of the individuals being transmutable,
+whilst the “species” are not transmutable at the same time, the line
+of the “species” being a fixed order, through which the “individuals”
+have to pass in the course of their generations. What is meant here
+will become clearer, when we study the different possible aspects of
+“phylogeny.”
+
+There are two different groups of facts which have suggested the idea
+of transformism: none of these facts can be said to be conclusive, but
+there certainly is a great amount of probability in the whole if taken
+together.
+
+The first group of evidences which lead to the hypothesis of the real
+relationship of organisms consists of facts relating to the geographical
+distribution of animals and plants and to palæontology. As to geography,
+it seems to me that the results of the floral and faunal study of groups
+of islands are to be mentioned in the first place. If, indeed, on
+each of the different islands, *A* *B* *C* and *D*, forming a group,
+the species of a certain genus of animals or plants are different in a
+certain respect, and show differences also compared with the species
+living on the neighbouring continent, of which there is geological
+evidence that the islands once formed a part, whilst there is no change
+in the species on the continent itself for very wide areas, then, no
+doubt, the hypothesis that all these differing species once had a common
+origin, the hypothesis that there is a certain community among them all,
+will serve to elucidate in some way what would seem to be very abstruse
+without it. And the same is true of the facts of palaeontology. In
+the geological strata, forming a continuous series, you find a set of
+animals, always typical and specific for every single stratigraphical
+horizon, but forming a series just as do those horizons. Would not the
+whole aspect of these facts lose very much of its peculiarity if you
+were to introduce the hypothesis that the animals changed with the
+strata? The continuity of life, at least, would be guaranteed by such an
+assumption.
+
+The geographical and geological evidences in favour of the theory of
+descent are facts taken from sciences which are not biology proper; they
+are not facts of the living but only facts about the living. That is not
+quite without logical importance, for it shows that not biology alone
+has led to the transformism hypothesis. Were it otherwise, transformism
+might be said to be a mere hypothesis *ad hoc*; but now this proves to
+be not the case, though we are far from pretending that transformism
+might be regarded as resting upon a real *causa vera*.
+
+But let us study the second group of facts which support the theory of
+descent. It is a group of evidences supplied by biology itself that we
+meet here, there being indeed some features in biology which can be
+said to gain some light, some sort of elucidation, if the theory of
+descent is accepted. Of course, these facts can only be such as relate
+to specific diversities, and indeed are facts of systematics; in other
+words, there exists something in the very nature of the system of
+organisms that renders transformism probable. The system of animals and
+plants is based upon a principle which might be called the principle
+of *similarities and diversities by gradation*; its categories are not
+uniform but different in degree and importance, and there are different
+kinds of such differences. No doubt, some light would be shed upon this
+character of the system, if we were allowed to assume that the relation
+between similarities and diversities, which is gradual, corresponded to
+a blood-relationship, which is gradual also.
+
+
+THE COVERT PRESUMPTION OF ALL THEORIES OF DESCENT
+
+We have used very neutral and somewhat figurative words, in order to
+show what might be called the logical value of the theory of descent,
+in order to signify its value with respect to so-called “explanation.”
+We have spoken of the “light” or the “elucidation” which it brings, of
+the “peculiarity of aspect” which is destroyed by it. We have used this
+terminology intentionally, for it is very important to understand that
+a specific though hidden addition is made almost unconsciously to the
+mere statement of the hypothesis of descent as such, whenever this
+hypothesis is advocated in order to bring light or elucidation into any
+field of systematic facts. And this additional hypothesis indeed must be
+made from the very beginning, quite irrespective of the more detailed
+problems of the law of transformism, in order that *any* sort of
+so-called explanation by means of the theory of descent may be possible
+at all. Whenever the theory that, in spite of their diversities, the
+organisms are related by blood, is to be really useful for explanation,
+it must necessarily be assumed in every case that the steps of change,
+which have led the specific form *A* to become the specific form *B*,
+have been such as only to change *in part* that original form *A*. That
+is to say: the similarities between *A* and *B* must never have become
+overshadowed by their diversities.
+
+Only on this assumption, which indeed is a newly formed additional
+subsidiary hypothesis, joined to the original hypothesis of descent in
+general--a hypothesis regarding the very nature of transformism--only
+on this almost hidden assumption is it possible to speak of any sort of
+“explanation” which might be offered by the theory of transformism to
+the facts of geography, geology, and biological systematics. Later on
+we shall study more deeply the logical nature of this “explanation”; at
+present it must be enough to understand this term in its quasi-popular
+meaning.
+
+What is explained by the hypothesis of descent--including the additional
+hypothesis, that there always is a prevalence of the similarities
+during transformism--is the fact that in palaeontology, in the groups
+of island and continent faunae and florae taken as a whole, as well as
+in the single categories of the system, the similarities exceed the
+diversities. The *similarities* now are “explained”; that is to say,
+they are understood as resting on but one principle: the similarities
+are understood as being due to inheritance;[144] and now we have but one
+problem instead of an indefinite number. For this reason Wigand granted
+that the theory of descent affords what he calls a numerical reduction
+of problems.
+
+[144] It seems to me that my argument gives a broader logical basis
+to the theory of descent than does that of G. Wolff (*Die Begründung
+der Abstammungslehre*, München, 1907). Wolff starts from the concept
+of organic teleology, and thus finds the only reason for accepting
+the theory of transformism in the existence of so-called “rudimentary
+organs”; these organs would form an obstacle to teleology if they could
+not be regarded as inherited.
+
+Understanding then what is explained by the theory of descent with its
+necessary appendix, we also understand at once what is *not* elucidated
+by it: the diversities of the organism remain as unintelligible as they
+always were, even if we know that inheritance is responsible for what
+is similar or equal. Now there can be no doubt that the diversities are
+the more important point in systematics; if there were only similarities
+there would be no problem of systematics, for there would be no system.
+Let us be glad that there are similarities in the diversities, and that
+these similarities have been explained in some way; but let us never
+forget what is still awaiting its explanation. Unfortunately it has been
+forgotten far too often.
+
+
+THE SMALL VALUE OF PURE PHYLOGENY
+
+And so we are led to the negative side of the theory of transformism,
+after having discussed its positive half. The theory of descent as
+such, without a real knowledge of the factors which are concerned in
+transformism, or of the law of transformism, in other terms, leaves the
+problem of systematics practically where it was, and adds really nothing
+to its solution. That may seem very deplorable, but it is true.
+
+Imagine so-called historical geology, without any knowledge of the
+physical and chemical factors which are concerned in it: what would
+you have except a series of facts absolutely unintelligible to you? Or
+suppose that some one stated the cosmogenetic theory of Kant and Laplace
+without there being any science of mechanics: what would the theory mean
+to you? Or suppose that the whole history of mankind was revealed to
+you, but that you had absolutely no knowledge of psychology: what would
+you have but facts and facts and facts again, with not a morsel of real
+explanation?
+
+But such is the condition in which so-called phylogeny stands. If it
+is based only on the pure theory of transformism, there is nothing
+explained at all. It was for this reason that the philosopher Liebmann
+complained of phylogeny that it furnishes nothing but a “gallery of
+ancestors.” And this gallery of ancestors set up in phylogeny is not
+even certain; on the contrary, it is absolutely uncertain, and very
+far from being a fact. For there is no sound and rational principle
+underlying phylogeny; there is mere fantastic speculation. How could it
+be otherwise where all is based upon suppositions which themselves have
+no leading principle at present? I should not like to be misunderstood
+in my polemics against phylogeny. I fully grant you that it may be
+possible in a few cases to find out the phylogenetic history of smaller
+groups with some probability, if there is some palaeontological
+evidence in support of pure comparative anatomy; and I also do not
+hesitate to allow that such a statement would be of a certain value with
+regard to a future discovery of the “laws” of descent, especially if
+taken together with the few facts known about mutations. But it is quite
+another thing with phylogeny on the larger scale. Far more eloquent than
+any amount of polemics is the fact that vertebrates, for instance, have
+already been “proved” to be descended from, firstly, the amphioxus;
+secondly, the annelids; thirdly, the *Sagitta* type of worms; fourthly,
+from spiders; fifthly, from *Limulus*, a group of crayfishes; and
+sixthly, from echinoderm larvae. That is the extent of my acquaintance
+with the literature, with which I do not pretend to be specially
+familiar. Emil du Bois-Reymond said once that phylogeny of this sort is
+of about as much scientific value as are the pedigrees of the heroes of
+Homer, and I think we may fully endorse his opinion on this point.
+
+
+HISTORY AND SYSTEMATICS
+
+A few words should be devoted to the relations between history and
+systematics in biology. Is there no contradiction between historical
+development and a true and rational system which, we conceded, might
+exist some day in biological sciences, even though it does not at
+present? By no means. A totality of diversities is regarded from quite
+different points of view if taken as the material of a system, and if
+considered as realised in time. We have said that chemistry has come
+very near to proper rational systematics, at least in some of its
+special fields; but the compounds it deals with at the same time may
+be said to have originated historically also, though not, of course,
+by a process of propagation. It is evident at once that the geological
+conditions of very early times prohibited the existence of certain
+chemical compounds, both organic and inorganic, which are known at
+present. None the less these compounds occupy their proper place in
+the system. And there may be many substances theoretically known to
+chemical systematics which have never yet been produced, on account
+of the impossibility of arranging for their proper conditions of
+appearance, and nevertheless they must be said to “exist.” “Existence,”
+as understood in systematics, is independent of special space and of
+special time, as is the existence of the laws of nature: we may speak of
+a Platonic kind of existence here. Of course it does not contradict this
+sort of ideal existence if reality proper is added to it.
+
+Thus the problem of systematics remains, no matter whether the theory
+of descent be right or wrong. There always remains the question about
+the totality of diversities in life: whether it may be understood by
+a general principle, and of what kind that principle would be. As,
+in fact, it is most probably by history, by descent, that organic
+systematics is brought about, it of course most probably will happen
+some day that the analysis of the causal factors concerned in the
+history will serve to discover the principle of systematics also.
+
+Let us now glance at the different kinds of hypotheses which have been
+established in order to explain how the descent of the organisms might
+have been possible. We have seen that the theory of transformism alone
+is not worth very much as a whole, unless at least a hypothetical
+picture can be formed of the nature of the transforming factors: it is
+by some such reasoning that almost every author who has defended the
+theory of descent in its universality tries to account for the manner in
+which organisms have acquired their present diversities.
+
+
+2. THE PRINCIPLES OF DARWINISM
+
+There is no need in our times and particularly in this country, to
+explain in a full manner the theory known under the name of Darwinism.
+All of you know this theory, at least in its outlines, and so we may
+enter at once upon its analytic discussion. A few words only I beg
+you to allow me as to the name of “Darwinism” itself. Strange to say,
+Darwinism, and the opinion of Charles Darwin about the descent of
+organisms, are two different things. Darwin, the very type of a man
+devoted to science alone and not to personal interests,--Darwin was
+anything but dogmatic, and yet Darwinism is dogmatism in one of its
+purest forms. Darwin, for instance, gave the greatest latitude to the
+nature of the variations which form the battleground of the struggle
+for existence and natural selection; and he made great allowances for
+other causal combinations also, which may come into account besides
+the indirect factors of transformism. He was Lamarckian to a very
+far-reaching extent. And he had no definite opinion about the origin
+and the most intimate nature of life in general. These may seem to
+be defects but really are advantages of his theory. He left open the
+question which he could not answer, and, in fact, he may be said to be a
+good illustration of what Lessing says, that it is not the possession
+of truth but the searching after it, that gives happiness to man. It was
+but an outcome of this mental condition that Darwin’s polemics never
+left the path of true scientific discussions, that he never in all his
+life abused any one who found reason to combat his hypotheses, and that
+he never turned a logical problem into a question of morality.
+
+How different is this from what many of Darwin’s followers have made out
+of his doctrines, especially in Germany; how far is “Darwinism” removed
+from Darwin’s own teaching and character!
+
+It is to Darwinism of the *dogmatic* kind, however, that our next
+discussions are to relate, for, thanks to its dogmatism, it has the
+advantage of allowing the very sharp formulation of a few causal
+factors, which *a priori* might be thought to be concerned in organic
+transformism, though we are bound to say that a really searching
+analysis of these factors ought to have led to their rejection from the
+very beginning.
+
+The logical structure of dogmatic Darwinism reveals two different parts,
+which have nothing at all to do with one another.
+
+
+NATURAL SELECTION
+
+We shall first study that part of it which is known under the title
+of natural selection, irrespective of the nature of the causes of
+primary differences, or, in other words, the nature of variability.
+This part may be said to belong to Darwin’s personal teachings and not
+only to “Darwinism.” The offspring of a certain number of adults show
+differences compared with each other; there are more individuals in the
+offspring than can grow up under the given conditions, therefore there
+will be a struggle for existence amongst them, which only the fittest
+will survive; these survivors may be said to have been “selected” by
+natural means.
+
+It must be certain from the very beginning of analysis that natural
+selection, as defined here, can only eliminate what cannot survive, what
+cannot stand the environment in the broadest sense, but that natural
+selection never is able to create diversities. It always acts negatively
+only, never positively. And therefore it can “explain”--if you will
+allow me to make use of this ambiguous word--it can “explain” only why
+certain types of organic specifications, imaginable *a priori*, do
+*not* actually exist, but it never explains at all the existence of the
+specifications of animal and vegetable forms that are actually found. In
+speaking of an “explanation” of the origin of the living specific forms
+by natural selection one therefore confuses the sufficient reason for
+the non-existence of what there is not, with the sufficient reason for
+the existence of what there is. To say that a man has explained some
+organic character by natural selection is, in the words of Nägeli, the
+same as if some one who is asked the question, “Why is this tree covered
+with these leaves,” were to answer “Because the gardener did not cut
+them away.” Of course that would explain why there are no more leaves
+than those actually there, but it never would account for the existence
+and nature of the existing leaves as such. Or do we understand in the
+least why there are white bears in the Polar Regions if we are told that
+bears of other colours could not survive?
+
+In denying any real explanatory value to the concept of natural
+selection I am far from denying the action of natural selection. On
+the contrary, natural selection, to some degree, is *self-evident*;
+at least as far as it simply states that what is incompatible with
+permanent existence cannot exist permanently, it being granted that
+the originating of organic individuals is not in itself a guarantee of
+permanency. Chemical compounds, indeed, which decompose very rapidly
+under the conditions existing at the time when they originated may also
+be said to have been eliminated by “natural selection.” It is another
+question, of course, whether in fact all eliminations among organic
+diversities are exclusively due to the action of natural selection in
+the proper Darwinian sense. It has been pointed out already by several
+critics of Darwinism and most clearly by Gustav Wolff, that there are
+many cases in which an advantage with regard to situation will greatly
+outweigh any advantage in organisation or physiology. In a railway
+accident, for instance, the passengers that survive are not those who
+have the strongest bones, but those who occupied the best seats; and
+the eliminating effect of epidemics is determined at least as much by
+localities, *e.g.* special houses or special streets, as by the degree
+of immunity. But, certainly, natural selection is a *causa vera* in many
+other cases.
+
+We now may sum up our discussion of the first half of Darwinism.
+Natural selection is a negative, an eliminating factor in transformism;
+its action is self-evident to a very large degree, for it simply
+states that things do not exist if their continuance under the given
+conditions is impossible. To consider natural selection as a positive
+factor in descent would be to confound the sufficient reason for the
+non-existence of what is not, with the sufficient reason of what is.
+
+Natural selection has a certain important logical bearing on
+systematics, as a science of the future, which has scarcely ever been
+alluded to. Systematics of course has to deal with the totality of the
+possible, not only of the actual diversities; it therefore must remember
+that more forms may be possible than are actual, the word “possible”
+having reference in this connection to originating, not to surviving.
+Moreover, systematics is concerned not only with what has been
+eliminated by selection, but also with all that might have originated
+from the eliminated types. By such reasoning natural selection gains a
+very important aspect--but a logical aspect only.
+
+
+FLUCTUATING VARIATION THE ALLEGED CAUSE OF ORGANIC DIVERSITY
+
+The second doctrine of dogmatic Darwinism states that all the given
+diversities among the organisms that natural selection has to work
+upon are offered to natural selection by so-called fluctuating
+variation; that is, by variation as studied by means of statistics.
+This sort of variation, indeed, is maintained to be indefinite in
+direction and amount, at least by the most conservative Darwinians; it
+has occasionally been called a real differential; in any case it is
+looked upon as being throughout contingent with regard to some unity
+or totality; which, of course, is not to mean that it has not had a
+sufficient reason for occurring.
+
+It could hardly be said to be beyond the realm of possibility that such
+differences among organic species as only relate to degree or quantity
+and perhaps to numerical conditions also, might have been “selected” out
+of given contingent variations, if but one postulate could be regarded
+as fulfilled. This postulate may appropriately be stated as the fixation
+of new averages of variation by inheritance. Let the average value of
+a variation, with regard to a given property of a given species be *n*
+and let the value *n* + *m*--*m* being variable--which is represented in
+fewer individuals of course than is *n*, be such as to offer advantages
+in the struggle for existence; then the individuals marked by *n* + *m*
+will have the greater chance of surviving. Our postulate now states
+that, in order that a permanent increase of the average value of the
+variation in question may be reached, *n* + *m* in any of its variable
+forms must be able to become the average value of the second generation,
+as *n* was the average value of the first. Out of the second generation
+again it would be the few individuals marked by *n* + *m* + *o*, which
+would be selected; *n* + *m* + *o* would be the new average; afterwards
+*n* + *m* + *o* + *p* would be selected, would become the new average,
+and so on. A black variety for instance might be selected by such a
+series of processes out of a grey-coloured one without difficulty.
+
+But our postulate is not beyond all doubt: certain experiments, at
+least, which have been carried out about the summation of variations
+of the true fluctuating type by any kind of selection seem to show
+that there may be a real progress for a few generations, but that this
+progress is always followed by a reversion. Of course our experience
+is by no means complete on this subject, and, indeed, it may be shown
+in the future that positive transforming effects of fluctuating
+variability, in connection with selective principles, are possible in
+the case of new quantitative differences (in the widest sense), but we
+are not entitled to say so at present.
+
+And this is the only condition on which we can give credit to the second
+doctrine of dogmatic Darwinism. Its second principle, indeed, proves
+to be absolutely inadequate to explain the origin of any other kind of
+specific properties whatever.
+
+I cannot enter here into the whole subject of Darwinian criticism.[145]
+Our aims are of a positive character, they desiderate construction
+and only use destruction where it is not to be avoided. So I shall
+only mention that dogmatic Darwinism has been found to be unable to
+explain every kind of mutual adaptations, *e.g.* those existing between
+plants and insects; that it can never account for the origin of those
+properties that are indifferent to the life of their bearer, being mere
+features of organisation as an arrangement of parts; that it fails in
+the face of all portions of organisation which are composed of many
+different parts--like the eye--and nevertheless are functional units
+in any passive or active way; and that, last not least, it has been
+found to be quite inadequate to explain the first origin of all newly
+formed constituents of organisation even if they are not indifferent:
+for how could any rudiment of an organ, which is not functioning at all,
+not only be useful to its bearer, but be useful in such a degree as to
+decide about life or death?
+
+[145] See Wigand, *Der Darwinismus und die Naturforschung Newton’s und
+Cuvier’s*, Braunschweig, 1874-7; Nägeli, *Mechanisch-physiologische
+Theorie der Abstammungslehre*, München, 1884; G. Wolff, *Beiträge zur
+Kritik der Darwin’schen Lehre*, 2nd ed. Leipzig, 1898; etc.
+
+It is only for one special feature that I should like to show, by
+a more full analysis, that dogmatic Darwinism does not satisfy the
+requirements of the case. The special strength of Darwinism is said to
+lie in its explaining everything that is useful in and for organisms;
+the competitive factor it introduces does indeed seem to secure at least
+a relative sort of adaptedness between the organism and its needs. But
+in spite of that, we shall now see that Darwinism fails absolutely to
+explain those most intimate organic phenomena which may be said to be
+the most useful of all.
+
+Darwinism in its dogmatic form is not able to explain the origin of any
+sort of organic restitution; it is altogether impossible to account for
+the restitutive power of organisms by the simple means of fluctuating
+variation and natural selection in the struggle for existence. Here we
+have the logical *experimentum crucis* of Darwinism.
+
+Let us try to study in the Darwinian style the origin of the
+regenerative faculty, as shown in the restitution of the leg of a
+newt. All individuals of a given species of the newt, say *Triton
+taeniatus*, are endowed with this faculty; all of them therefore must
+have originated from ancestors which acquired it at some time or other.
+But this necessary supposition implies that all of these ancestors must
+have lost their legs in some way, and not only one, but all four of
+them, as they could not have acquired the restitutive faculty otherwise.
+We are thus met at the very beginning of our argument by what must be
+called a real absurdity, which is hardly lessened by the assumption that
+regeneration was acquired not by all four legs together, but by one
+after the other. But it is absolutely inevitable to assume that *all*
+the ancestors of our *Triton* must have lost one leg, or more correctly,
+that only those of them survived which had lost one! Otherwise not all
+newts at the present day could possess the faculty of regeneration! But
+a second absurdity follows the first one; out of the ancestors of our
+newt, which survived the others by reason of having lost one of their
+legs, there were selected only those which showed at least a very small
+amount of healing of their wound. It must be granted that such a step
+in the process of selection, taken by itself, would not at all seem to
+be impossible; since healing of wounds protects the animals against
+infection. But the process continues. In every succeeding stage of it
+there must have survived only those individuals which formed just a
+little more of granulative tissue than did the rest: though *neither*
+they themselves *nor* the rest could use the leg, which indeed was
+not present! That is the second absurdity we meet in our attempt at a
+Darwinian explanation of the faculty of regeneration; but I believe the
+first one alone was sufficient.
+
+If we were to study the “selection” of the faculty of one of the
+isolated blastomeres of the egg of the sea-urchin to form a whole larva
+only of smaller size, the absurdities would increase. At the very
+beginning we should encounter the absurdity, that of all the individuals
+there survived only those which were not whole but half; for *all*
+sea-urchins are capable of the ontogenetical restitution in question,
+*all* of their ancestors therefore must have acquired it, and they
+could do that only *if* they became halved at first by some accident
+during early embryology. But we shall not insist any further on this
+instance, for it would not be fair to turn into ridicule a theory which
+bears the name of a man who is not at all responsible for its dogmatic
+form. Indeed, we are speaking against Darwinism of the most dogmatic
+form only, not against Darwin himself. He never analysed the phenomena
+of regeneration or of embryonic restitution--they lay in a field very
+unfamiliar to him and to his time. I venture to say that if he had taken
+them into consideration, he would have agreed with us in stating that
+his theory was not at all able to cover them; for he was prepared to
+make great concessions, to Lamarckism for instance, in other branches of
+biology, and he did not pretend, to know what life itself is.
+
+Darwin was not a decided materialist, though materialism has made
+great capital out of his doctrines, especially in Germany. His book,
+as is well known, is entitled “The Origin of *Species*,” that is of
+organic *diversities*, and he himself possibly might have regarded all
+restitution as belonging to the original properties of life, anterior to
+the originating of diversities. Personally he might possibly be called
+even a vitalist. Thus dogmatic “Darwinism” in fact is driven into all
+the absurdities mentioned above, whilst the “doctrine of Darwin” can
+only be said to be wrong on account of its failing to explain mutual
+adaptation, the origin of new organs, and some other features in organic
+diversities; the original properties of life were left unexplained by it
+intentionally.
+
+
+DARWINISM FAILS ALL ALONG THE LINE
+
+The result of our discussion then must be this: selection has proved to
+be a negative factor only, and fluctuating variation as the only way
+in which new properties of the organisms might have arisen has proved
+to fail in the most marked manner, except perhaps for a few merely
+quantitative instances. Such a result betokens the complete collapse
+of dogmatic Darwinism as a general theory of descent: the most typical
+features of all organisms remain as unexplained as ever.
+
+What then shall we put in the place of pure Darwinism? Let us first try
+a method of explanation which was also adopted occasionally by Darwin
+himself: let us study that form of transformation theories which is
+commonly known under the title of Lamarckism.
+
+
+3. THE PRINCIPLES OF LAMARCKISM.
+
+As the word “Darwinism” does not signify the proper theoretical system
+of Charles Darwin, so Lamarckism as commonly understood nowadays is a
+good deal removed from the original views of Jean Baptiste Lamarck.
+Lamarckism is generally regarded as reducing all organic diversities to
+differences in the needs of individual life, but Lamarck himself, as
+must be emphasised from the very beginning, did not at all maintain the
+opinion that the great characteristics of the types were only due to
+such accidental factors. He supposed a sort of law of organisation to
+be at the root of systematics, as developed in history, and the needs
+of life were only responsible, according to him, for splitting the
+given types of organisation into their ultimate branches. Thus Lamarck,
+to a great extent at any rate, belongs to a group of authors that we
+shall have to study afterwards: authors who regard an unknown law of
+phylogenetic development as the real basis of transformism. Modern
+so-called Neo-Lamarckism, on the other hand, has indeed conceded the
+principle of needs to be the sole principle of transformism. Let us then
+study Lamarckism in its dogmatic modern form.
+
+
+ADAPTATION AS THE STARTING-POINT
+
+All facts of morphological adaptations--facts which we have analysed
+already from a different point of view, as being among the most typical
+phenomena of organic regulation--form the starting-point of this
+theory, and it must be granted that they form a very solid foundation,
+for they are facts. The theory only has to enlarge hypothetically the
+realm of these facts, or rather the realm of the law that governs them.
+Indeed, it is assumed by Lamarckism that the organism is endowed with
+the faculty of responding to *any* change of the environment which may
+change its function by a morphologically expressed alteration of its
+functional state and form, which is adapted to the state of conditions
+imposed from without. Of course, as stated in this most general form,
+the assumption is not true, but it is true within certain limits, as
+we know; and there seems to be no reason why we should not believe
+that there are many more cases of adaptation than we actually know at
+present, or that, in former phylogenetic times, the organisms were more
+capable of active adaptation than they are now. So to a certain extent,
+at least, Lamarckism can be said to rest upon a *causa vera*.
+
+It is important to notice that this *causa vera* would imply vitalistic
+causality when taken in the wide meaning which Lamarckism allows to
+it: indeed, the power of active adaptation to indefinite changes would
+imply a sort of causal connection that is nowhere known except in the
+organism. Lamarck himself is not very clear about this point, he seems
+to be afraid of certain types of uncritical vitalism in vogue in his
+days; but modern writers have most clearly seen what the logical
+assumptions of pure Lamarckism are. Next to Cope, August Pauly[146] may
+be said to be the most conscious representative of a sort of so-called
+psychological vitalism, which indeed Lamarckism as a general and
+all-embracing theory must have as its basis.
+
+[146] *Darwinismus und Lamarckismus*, München, 1905.
+
+
+THE ACTIVE STORING OF CONTINGENT VARIATIONS AS A HYPOTHETIC PRINCIPLE
+
+This point will come out more fully, if now we turn to study a certain
+group of principles, upon which dogmatic Lamarckism rests: I say
+principles and not facts, for there are no facts but only hypothetic
+assumptions in this group of statements. We do know a little about
+adaptations, at least to a certain extent, and it was only about the
+sphere of the validity of a law, which was known to be at work in
+certain cases, that hypothetical additions were made. In the second
+group of the foundations of Lamarckism we know absolutely nothing;
+accidental variations of form are supposed to occur, and the organism is
+said to possess the faculty of keeping and storing these variations and
+of handing them down to the next generation, if they happen to satisfy
+any of its needs.
+
+But these needs are not of the actual type, brought forth by a change of
+the functional state of the individual, as in the case of adaptations:
+they are of a somewhat mysterious nature. A glance at the theory of the
+origin of the movements which are called acts of volition in the human
+child may serve to elucidate what is meant.
+
+Acts of volition are said thus to originate in random movements of the
+new-born infant: certain of these accidental motions which happen to
+relieve some pain or to afford some pleasure are “remembered,” and are
+used another time quite consciously to bring forth what is liked or to
+remove what is disliked. So much for the present on a very difficult
+subject, which will occupy us next year at much greater length. It is
+clear that at least three fundamental phenomena are concerned in this
+theory of the origin of acts of volition: the liking and disliking, the
+keeping in mind, and the volition itself. The real act of volition,
+indeed, is always based upon a connection of all these factors, these
+factors now being connected in such a way that even their kind of
+connection may be said to be a fourth fundamental principle. In order
+that the particular effect may be obtained which is wanted because it is
+liked, the possible ways leading to it, which appeared among the random
+movements in the very beginning, are now regarded as “means” and may now
+be said to be “used.” But that is as much as to say that the “means”
+are judged with respect to their usefulness for the actual purpose, and
+therefore *judgment* is the fourth foundation of the act of volition.
+
+In fact, Pauly does not hesitate to attribute judgment, along with the
+other psychological elements, to the organisms whilst undergoing their
+transformation. There has been formed, for instance, by accidental
+variation some pigment which by its chemical nature brings the organism
+into a closer connection with the light of the medium; the individual
+likes that, keeps the pigment for itself and produces it again in the
+next generation; and indeed it will safeguard any sort of improvement
+which chance may effect in this primitive “eye.” Such a view is said
+to hold well with respect to the origin of every new organ. And this
+psychological argument is also said to afford the real explanation of
+adaptation proper. Adaptation also is regarded not as a truly primary
+faculty of the organism, but as a retention or provoking of metabolic
+states which occurred by accident originally and were then found to
+be useful; now they are reproduced either in every single case of
+individual morphogenesis, without regard to actual requirements, or
+else only in response to such: in the first case they are “inherited,”
+in the second they only occur as regulations. Thus the process of
+judgment, together with all the other elemental factors of psychical
+life concerned in it, has been made to account for adaptation proper.
+The whole theory has accordingly become very uniform and simple.
+
+
+CRITICISM OF THE “INHERITANCE OF ACQUIRED CHARACTERS” ASSUMED BY
+LAMARCKISM
+
+In addressing ourselves to the criticism of Neo-Lamarckism we shall
+neglect as far as possible all the different psychological principles
+concerned in it--which in any case would need rather a great amount of
+epistemological sifting--and shall keep to those hypothetic facts which
+are supposed to be such as may be actually observed in nature.
+
+All of you know that the so-called inheritance of acquired characters
+lies at the root of Lamarckism; and from this hypothesis our critical
+analysis is to start, disregarding a larger or smaller number of
+psychological principles that are brought into the field.
+
+The name of “acquired characters” may *a priori* be given to three
+different types of phenomena: firstly, variations including mutations;
+secondly, disease or injuries; and thirdly, the results of the actual
+process of adaptation of every kind.
+
+In the first of these groups, the true problem of the inheritance of
+“acquired” characters appears only with certain restrictions. All
+variations and mutations are indeed “acquired” by one generation so
+far as the earlier generation did not possess them, but mutations, at
+least, cannot be said to be acquired by the actual adult personality:
+they are innate in it from its very beginning, and therefore may better
+be called congenital.[147] Congenital properties of the mutation type
+are, in fact, known to be inherited: their inheritance does not present
+any problem of its own, but is included in the changes of the hereditary
+condition to which they are due altogether.[148] All properties of the
+variation type, on the other hand, having been studied statistically,
+are known to be inherited, to a certain small extent, as we have seen
+already whilst studying Darwinism, though they are possibly always
+liable to reversion. Modern science, as we know,[149] regards them as
+due to changes of nutrition, in the most general meaning of the word.
+Under such a view variations might indeed be said to belong to the
+acquired group of organic specifications; their inheritance, as will
+be seen later on, would hardly be quite a pure instance of what we are
+searching for. In no case can true variations claim to be of great
+importance in problems of transformism.
+
+[147] This would not be true, if the varieties of plants produced by
+Blaringhem, Klebs, and MacDougal by means of *external* agents were
+really “mutations” (comp. page 238, note 3).
+
+[148] Of course, the inheritance of mutations would imply a certain sort
+of “inheritance of acquired characters,” on the condition stated in the
+preceding note. But, probably, the germs of the next generation might
+be regarded here as being directly affected by the external agent, in a
+manner that will briefly be mentioned later on in the text.
+
+[149] Comp. page 238, note 2.
+
+But what is known about the inheritance of those properties which
+beyond any doubt may be said to have originated in the adult individual
+as such, and of which lesions and adaptations proper, as shown for
+instance among amphibious plants, are instances of the two most
+typical groups?[150] Weismann did good service by putting an end to
+the scientific credulity which prevailed with regard to this subject.
+Weismann was led by his theory of the germ plasm to deny the inheritance
+of acquired characters of the typical kinds. He could not imagine how
+the effect of any agent upon the adult, be it of the merely passive or
+of the adaptive kind, could have such an influence upon the germ as to
+force it to produce the same effect in spite of the absence of that
+agent. In fact, that is what the inheritance of acquired characters
+would render necessary, and a very strange phenomenon it would be,
+no doubt. But, of course, taken alone, it could never be a decisive
+argument against such inheritance. I fully agree, that science is
+obliged to explain new facts by what is known already, as long as it is
+possible; but if it is no longer possible, the theory of course has to
+be changed, and not the facts. On this principle one would not neglect
+the fact of an inheritance of acquired properties, but on the contrary
+one perhaps might use it as a new evidence of vitalism.
+
+[150] Certain English authors have applied the term “modification” to
+all kinds of organic properties acquired from without, whether they are
+adapted or not.
+
+But are there any facts?
+
+At this point we come to speak about the second group of Weismann’s
+reasonings. He not only saw the difficulty of understanding inheritance
+of acquired characters on the principles of the science of his time,
+but he also criticised the supposed facts; and scarcely any of them
+stood the test of his criticism. Indeed, it must fairly be granted that
+not one case is known which really proves the inheritance of acquired
+characters, and that injuries certainly are never found to be inherited.
+In spite of that, I do not believe that we are entitled to deny the
+possibility of the inheritance of a certain group of acquired characters
+in an absolute and dogmatic manner, for there are a few facts which seem
+at least to tend in the direction of such an inheritance, and which seem
+to show that it might be discovered perhaps one day, if the experimental
+conditions were changed.
+
+I am not referring here to the few cases in which bacteria were made
+colourless or non-virulent by outside factors, or in which certain
+fungi were forced to permanent agamic reproduction by abnormal external
+conditions and were shown to retain their “acquired properties”
+after the external conditions had been restored. In these cases only
+reproduction by simple division occurred, and that does not imply the
+true problem of inheritance. Nor am I referring to the few cases of
+non-adaptive “modifications” found by Standfuss and Fischer, in which
+butterflies that had assumed an abnormal kind of pigmentation under
+the influence of abnormal temperature acting upon the pupa, were seen
+to form this same kind of pigmentation in the next generation under
+normal conditions of temperature. These cases, though important in
+themselves, are capable perhaps of a rather simple explanation, as in
+fact has been suggested. Some necessary means both of inheritance and of
+morphogenesis, the former being present in the propagation cells, may
+be said to have been changed or destroyed by heat, and therefore, what
+seems to be inherited after the change of the body only, would actually
+be the effect of a direct influence of the temperature upon the germ
+itself.[151] Let me be clearly understood: I do not say that it is so,
+but it may be so. What seems to me to be more important than everything
+and to have a direct bearing on the real discovery of the inheritance
+of acquired characters in the future, is this. In some instances
+plants which had been forced from without to undergo certain typical
+morphological adaptations, or at least changes through many generations,
+though they did not keep the acquired characters permanently in spite
+of the conditions being changed to another type, were yet found to lose
+the acquired adaptations not suddenly but only in the course of three
+or more generations. A certain fern, *Adiantum*, is known to assume a
+very typical modification of form and structure, if grown on serpentine;
+now Sadebeck,[152] while cultivating this serpentine modification of
+*Adiantum* on ordinary ground, found that the first generation grown in
+the ordinary conditions loses only a little of its typical serpentine
+character, and that the next generation loses a little more, so that
+it is not before the fifth generation that all the characters of the
+serpentine modification have disappeared. There are a few more cases
+of a similar type relating to plants grown in the plains or on the
+mountains. There also it was found to take time, or rather to take the
+course of *several* generations, until what was required by the new
+conditions was reached. Of course these cases are very very few compared
+with those in which a *sudden* change of the adaptive character,
+corresponding to the actual conditions, sets in; but it is enough that
+they do exist.
+
+[151] Of course the inheritance of specific values from the results of
+fluctuating variations, leading to new averages of variability (see
+p. 265), may also be understood in this manner, the conditions of
+nourishment acting upon the adult and upon its germs equally well.
+
+[152] *Berichte üb. d. Sitzung. d. Ges. f. Bot.*, Hamburg, 1887, 3 Heft.
+
+Would it not be possible at least that adaptations which last
+for thousands of generations or more might in fact change the
+adaptive character into a congenital one? Then we not only should
+have inheritance of acquired characters, but should have a sort
+of explanation at the same time for the remarkable fact that
+certain histological structures of a very adapted kind are formed
+ontogenetically before any function exists, as is known to be the
+case with the structures in the bones of vertebrates, for instance.
+Experiments are going on at Paris, and perhaps in other places of
+scientific research also, which, it is hoped, will show that animals
+reared in absolute darkness for many generations will lose their
+perfectly formed eyes, and that animals from the dark with very
+rudimentary eyes will be endowed with properly functioning ones, after
+they have been reared in the light for generations. Such a result indeed
+would account for the many animals, of the most different groups, which
+live in dark caves and possess only rudiments of eyes: functional
+adaptation is no longer necessary, so-called atrophy by inactivity sets
+in, and the results “acquired” by it are inherited.[153]
+
+[153] Quite recently Kammerer (*Arch. Entw. Mech.* 25, 1907, p. 7) has
+published very important experiments on the inheritance of “acquired”
+modifications with regard to the peculiarities of reproduction in
+*Salamandra atra* and *S. maculosa*. It seems rather improbable--though
+not absolutely impossible--that the germ cells were directly affected by
+the external modifying agent in this case.
+
+But enough of possibilities. Let us be content at present to know at
+least a few real instances with regard to the slowness of the process of
+what might be said to be “re-adaptation” in some plants. This process
+shows us a way by which our problem may some day be solved; it allows
+us to introduce inheritance of acquired characters as a legitimate
+hypothesis at least, which not only will explain many of the diversities
+in systematics historically, but also can be called, though not a *causa
+vera*, yet certainly more than a mere fiction.
+
+
+OTHER PRINCIPLES WANTED
+
+We have only dealt with the probability of the inheritance of
+morphological or physiological[154] adaptation. If that could really be
+considered as one of the factors concerned in the theory of descent,
+many, if not all of those congenital diversities among organic species
+which are of the type of a true structural correspondence to their
+future functional life, might be regarded as explained, that is,
+as reduced to one and the same principle. But nothing more than an
+explanation of *this* kind of diversities is effected by our principle,
+and very much more remains to be done, for organic diversities not only
+consist in specifications and differences as to histology, but are to a
+much more important degree, differences of organisation proper, that is,
+of the arrangement of parts, in the widest sense of the word.[155]
+
+[154] We have not spoken about the hypothetic inheritance of pure
+physiological adaptations, for it is clear without further discussion
+that innate specific immunity, for instance, being a specific
+“adaptedness” (*see* p. 186) *might* be due to the inheritance of the
+results of active immunity as an adaptation, just as adaptive congenital
+structures *might* be due to such an inheritance.
+
+[155] C. E. v. Baer clearly discriminated between the type, the degree
+of organisation, and the histological structure. All these three topics
+indeed have to be taken into account separately; the third alone is of
+the adaptive type. All of them may be independent of each other: the
+Amoeba may be as adapted histologically as is a high vertebrate, but it
+is of much lower type; and in its own type it is of a lower degree of
+organisation than Radiolaria are.
+
+Would it be possible to interpret the origin of this sort of systematic
+diversities by a reasoning similar to that by which we have understood,
+at least hypothetically, congenital adaptedness?
+
+Dogmatic Lamarckism, we know, uses two principles as its foundations;
+one of them, adaptation and its inheritance, we have studied with what
+may be called a partly positive result. The other is the supposed
+faculty of the organism to keep, to store, and to transfer those
+variations or mutations of a not properly adaptive sort which, though
+originating by chance, happen to satisfy some needs of the organism.
+
+
+CRITICISM OF THE HYPOTHESIS OF STORING AND HANDING DOWN CONTINGENT
+VARIATIONS
+
+Strange to say, this second hypothesis of dogmatic Lamarckism, invented
+with the express purpose of defeating Darwinism and taking the place of
+its fluctuating variability, which was found not to do justice to the
+facts--this second hypothesis of dogmatic Lamarckism is liable to just
+the same objections as dogmatic Darwinism itself.
+
+As it is important to understand well the real logical nature of
+our objections to both of the great transformistic theories, we
+think it well to interrupt our argument for a moment, in order to
+consider a certain point which, though very important in itself,
+seems of only secondary importance to us in our present discussion.
+Dogmatic Darwinism--I do not say the doctrine of Charles Darwin--is
+materialistic at bottom, and indeed has been used by many to complete
+their materialistic view of the universe on its organic side. The word
+“materialism” must not necessarily be taken here in its metaphysical
+sense, though most materialists are dogmatic metaphysicians. It also
+can be understood as forming part of a phenomenological point of view.
+Materialism as a doctrine of science means simply this: that whether
+“nature” be reality or phenomenon, in any case there is but one ultimate
+principle at its base, a principle relating to the movements of
+particles of matter. It is this point of view which dogmatic Darwinism
+strengthens; on the theory of natural selection and fluctuating
+variations, due to accidental differences of nutrition, organisms are
+merely arrangements of particles of matter, nothing else; and moreover,
+their kinds of arrangement are understood, at least in principle.
+Lamarckism, on the other hand, is not materialistic, but most markedly
+vitalistic--psychistic even; it takes life for granted when it begins
+its explanations.
+
+You may tell me that Darwin did the same, that he expressly states that
+his theory has nothing to do with the origin of life; that the title
+of his work is “The Origin of *Species*.” It would certainly be right
+to say so, at least with reference to Darwin personally; but in spite
+of that, it must be granted that Darwin’s doctrine contains a certain
+germ of materialism which has been fully developed by the Darwinian
+dogmatists, while Lamarckism is antimaterialistic by its very nature.
+
+Now it is very important, I think, to notice that this difference
+between the two theories is unable to disguise one main point which is
+common to both: and it is to this point, and to this point only, that
+our chief objections against both these theories converge at present.
+
+The *contingency* of the typical organic form is maintained by Darwinism
+as well as by Lamarckism: both theories, therefore, break down for
+almost the same reasons. The term “contingency” can signify very
+different relations, having but little in common; but it is sufficient
+for our present purpose to observe that there may be distinguished
+roughly two main classes of contingencies, which may provisionally be
+called the “contingency of being,” and the “contingency of occurring.”
+It is with the contingency of being that criticism of Darwinism and
+Lamarckism of the dogmatic type has to deal. Darwinism dealt with
+variations occurring at random; the organic form was the result of
+a fixation of only one kind of such variations, all others being
+extinguished by selection. In other terms, the specific organised
+form, as understood by Darwinism, was a unit only to the extent that
+all its properties related to one and the same body, but for the rest
+it was a mere aggregation or summation. It may be objected to this
+statement, that by being inherited in its specificity the Darwinian
+form proved to be a unit in a higher sense of the word, even in the
+opinion of dogmatic Darwinians; and this objection, perhaps, holds good
+as far as inheritance is concerned. But on the other hand, it must
+never be forgotten that the word “unit” had quite a vague and empty
+meaning even then, as indeed everything the organism is made up of
+is regarded as being in itself due to a contingent primary process,
+which has no relation to its fellow-processes. “Unit,” indeed, in spite
+of inheritance--which, by the way, is alleged also to be a merely
+materialistic event--means to Darwinians no more when applied to the
+organism than it does when applied to mountains or islands, where of
+course a sort of “unit” also exists in some sense, as far as one and the
+same body comes into account, but where every single character of this
+unit, in every single feature of form or of quality, is the result of
+factors or agents each of which is independent of every other.
+
+To this sort of contingency of being, as maintained by Darwinians,
+criticism has objected, as we know, that it is quite an impossible
+basis of a theory of descent, since it would explain neither the first
+origin of an organ, nor any sort of harmony among parts or among whole
+individuals, nor any sort of restitution processes.
+
+Now Lamarckism of the dogmatic kind, as will easily be seen, only
+differs from Darwinism in this respect, that what according to the
+latter happens to the organism passively by means of selection, is
+according to the former performed actively by the organism, by means of
+a “judgment”--by the retention and handing down of chance variations.
+The specificity of the form as a whole is contingent also according
+to Lamarckism. And, indeed, criticism must reject this contingency of
+being in exactly the same way as it rejected the contingency of form
+maintained by Darwinians.
+
+As far as the inheritance of truly adaptive characters comes into
+account--that is, the inheritance of characters which are due to the
+active faculty of adaptation possessed by the organism, bearing a
+vitalistic aspect throughout--hardly anything could be said against
+Lamarckism, except that inheritance of acquired characters is still
+an hypothesis of small and doubtful value at present. But that
+*specific organisation proper* is due to *contingent* variations, which
+accidentally have been found to satisfy some needs of the individual and
+therefore have been maintained and handed down, this reasoning is quite
+an impossibility of exactly the same kind as the argument of Darwinism.
+
+The process of restitution, perfect the very first time it occurs, if it
+occurs at all, is again the classical instance against this new sort of
+contingency, which is assumed to be the basis of transformism. Here we
+see with our eyes that the organism can do more than simply perpetuate
+variations that have occurred at random and bear in themselves no
+relation whatever to any sort of unit or totality. There *exists* a
+faculty of a certain higher degree in the organism, and this faculty
+cannot possibly have originated by the process which Lamarckians[156]
+assume. But if their principle fails in one instance, it fails as a
+*general* theory altogether. And now, on the other hand, as we actually
+see the individual organism endowed with a morphogenetic power,
+inexplicable by Lamarckism, but far exceeding the organogenetic faculty
+assumed by that theory, would it not be most reasonable to conclude from
+such facts, that there exists a certain organising power at the root of
+the transformism of species also, a power which we do not understand,
+which we see only partially manifested in the work of restitutions,
+but which certainly is not even touched by any of the Lamarckian
+arguments? There does indeed exist what Gustav Wolff has called primary
+purposefulness (“primäre Zweckmässigkeit”), at least in restitutions,
+and this is equally unexplainable by Darwinism and by the dogmatism of
+the Lamarckians.
+
+[156] I repeat once more that we are dealing here with dogmatic
+“Neo-”Lamarckism exclusively. This theory indeed claims to explain *all*
+features and properties of organic bodies on the basis of the feeling
+of needs and storing of contingent fulfilments and on this basis alone,
+just as dogmatic “Neo”-Darwinism claims to account for *all* those
+phenomena on the ground of contingent variations and natural selection.
+Darwin himself, as we have seen, intentionally left unexplained certain
+primary features of life and therefore cannot be blamed for having
+failed to explain them, though even then his theory remains wrong.
+Lamarck personally considered a real primary organisatory law of
+phylogeny as being of fundamental importance, and therefore he is not in
+the least responsible if “Neo-Lamarckism” fails as a universal theory.
+
+But before entering into this area of hypothesis, let us mention a few
+more objections to be made to the theory of the contingency of form as
+put forward by Lamarckians. In the first place, let us say a few words
+about the appropriateness of the term “contingency” as used in this
+connection. The forms are regarded as contingent by Lamarckians inasmuch
+as the variations which afterwards serve as “means” to the “needs” of
+the organism occur quite accidentally with regard to the whole organism.
+It might be said that these “needs” are not contingent but subject
+to an inherent destiny, but this plea is excluded by the Lamarckians
+themselves, when they say that the organism experiences no need until it
+has enjoyed the accidental fulfilment of the same. So the only thing in
+Lamarckian transformism which is not of a contingent character would be
+the psychological agent concerned in it, as being an agent endowed with
+the primary power of feeling needs after it has felt fulfilment, and of
+judging about what the means of future fulfilment are, in order to keep
+them whenever they offer. But these are characteristics of life itself,
+irrespective of all its specific forms, which alone are concerned in
+transformism. Now indeed, I think, we see as clearly as possible that
+Darwinism and Lamarckism, in spite of the great contrast of materialism
+and psychologism, shake hands on the common ground of the contingency of
+organic forms.
+
+The whole anti-Darwinistic criticism therefore of Gustav Wolff for
+instance, may also be applied to Lamarckism with only a few changes
+of words. How could the origin of so complete an organ as the eye of
+vertebrates be due to contingent variations? How could that account for
+the harmony of the different kinds of cells in this very complicated
+organ with each other and with parts of the brain? And how is it to be
+understood, on the assumption of contingency, that there are two eyes of
+almost equal perfection, and that there are two feet, two ears? Islands
+and mountains do not show such symmetry in *their* structures.
+
+We shall not repeat our deduction of the origin of restitutions, of
+regeneration for instance, on the dogmatic Lamarckian theory. As we
+have said already, it would lead to absurdities as great as in the
+case of dogmatic Darwinism, and indeed we already have mentioned that
+Lamarckians would hardly even attempt to explain these phenomena.
+It follows that dogmatic Lamarckism fails as a general theory about
+form.[157]
+
+[157] Compare also the excellent criticism of Lamarckism lately given by
+G. Wolff, *Die Begründung der Abstammungslehre*, München, 1907.
+
+There is finally one group of facts often brought forward against
+Lamarckism by Darwinian authors[158] which may be called the logical
+*experimentum crucis* of this doctrine, an *experimentum* destined
+to prove fatal. You know that among the polymorphic groups of bees,
+termites, and ants, there exists one type of individuals, or even
+several types, endowed with some very typical features of organisation,
+but at the same time absolutely excluded from reproduction: how could
+those morphological types have originated on the plan allowed by the
+Lamarckians? Of what use would “judgment” about means that are offered
+by chance and happen to satisfy needs, be to individuals which die
+without offspring? Here Lamarckism becomes a simple absurdity, just as
+Darwinism resulted in absurdities elsewhere.
+
+[158] It has also very often been said by Darwinians that Lamarckism is
+only able to explain those cases of adaptedness which relate to active
+functioning but not mere passive adapted characters, like “mimicry” for
+example. But this argument *taken by itself*, it seems to me, would not
+be fatal to Neo-Lamarckism in the special form August Pauly gave to this
+doctrine.
+
+We were speaking about dogmatic Darwinism then, and it is about dogmatic
+Lamarckism that we are reasoning at present; both theories must fall in
+their dogmatic form, though a small part of both can be said to stand
+criticism. But these two parts which survive criticism, one offered by
+Lamarck, the other by Darwin, are far from being a complete theory of
+transformism, even if taken together: they only cover a small area of
+the field concerned in the theory of descent. Almost everything is still
+to be done, and we may here formulate, briefly at least, what we expect
+to be accomplished by the science of the future.
+
+
+4. THE REAL RESULTS AND THE UNSOLVED PROBLEMS OF TRANSFORMISM
+
+What has been explained to a certain extent by the two great theories
+now current is only this. Systematic diversities consisting in mere
+differences as to intensity or number may perhaps owe their origin to
+ordinary variation. They may at least, if we are entitled to assume
+that heredity in some cases is able to hand on such variations without
+reversion, which, it must be again remarked, is by no means proved by
+the facts at present. Natural selection may share in this process by
+eliminating all those individuals that do not show the character which
+happens to be useful. That is the Darwinian part of an explanation of
+transformism which may be conceded as an hypothesis. On the other side,
+congenital histological adaptedness may be regarded hypothetically as
+due to an inheritance of adaptive characters which had been acquired by
+the organism’s activity, exerted during a great number of generations.
+That is the Lamarckian part in the theory of descent.
+
+But nothing more is contributed to this theory either by the doctrine
+of Darwin or by that of Lamarck. So it follows that almost everything
+has still to be done; for no hypothesis at present accounts for
+the foundation of all systematics, viz., for the differences in
+organisation, in all that relates to the so-called types as such and
+the degree of complication in these types, both of which (types and
+degree of complication) are independent of histological adaptation and
+adaptedness.
+
+What then do we know about any facts that might be said to bear on
+this problem? We have stated already at the end of our chapter devoted
+to the analysis of heredity that what we actually know about any
+deviation of inheritance proper, that is, about congenital differences
+between the parents and the offspring, relating to mere tectonics,
+is practically nothing: indeed, there are at our disposal only the
+few facts observed by de Vries or derived from the experience of
+horticulturalists and breeders. We may admit that these facts at
+least prove the possibility[159] of a discontinuous variation, that
+is of “mutation,” following certain lines of tectonics and leading to
+*constant* results; but everything else, that is everything about a real
+theory of phylogeny, must be left to the taste of each author who writes
+on the theory of the Living. You may call that a very unscientific state
+of affairs, but no other is possible.
+
+[159] But nothing more. All “mutations” hitherto observed in nature
+or (comp. page 238, note 3) experimentally produced relate only to
+“varieties” and not to “species.” One could hardly say that the
+recent investigations about the production of mutations by *external*
+means have strengthened their importance for the general theory of
+transformism.
+
+And, in fact, it has been admitted by almost all who have dealt with
+transformism without prepossessions that such is the state of affairs.
+Lamarck himself, as we have mentioned already, was not blind to the fact
+that a sort of organisatory law must be at the base of all transformism,
+and it is well known that hypothetical statements about an original law
+of phylogeny have been attempted by Nägeli, Kölliker, Wigand, Eimer,
+and many others. But a full discussion of all these “laws” would hardly
+help us much in our theoretical endeavour, as all of them, it must be
+confessed, do little more than state the mere fact that some unknown
+principle of organisation must have been at work in phylogeny, if we are
+to accept the theory of descent at all.
+
+It is important to notice that even such a convinced Darwinian as
+Wallace, who is well known to have been an independent discoverer of the
+elimination principle, admitted an exception to this principle in at
+least one case--with regard to the origin of man. But one exception of
+course destroys the generality of a principle.
+
+As we ourselves feel absolutely incapable of adding anything specific
+to the general statement that there *must* be an unknown principle of
+transformism, if the hypothesis of descent is justified at all, we may
+here close our discussion of the subject.
+
+
+5. THE LOGICAL VALUE OF THE ORGANIC FORM ACCORDING TO THE DIFFERENT
+TRANSFORMISTIC THEORIES
+
+A few words only must be added about two topics: on the character of
+organic forms as regarded by the different transformistic theories, and
+on the relation of transformism in general to our concept of entelechy.
+
+We have learnt that both Darwinism and Lamarckism, in their dogmatic
+shape, regard the specific forms of animals and plants as being
+contingent; in fact, it was to this contingency that criticism was
+mainly directed. We therefore are entitled to say that to Darwinism and
+Lamarckism organic forms are accidental in the very sense of the *forma
+accidentalis* of the old logicians. There are indefinite forms possible,
+according to these theories, and there is no law relating to these
+forms. Systematics, under such a view, must lose, of course, any really
+fundamental importance. “There is no rational system about organisms”:
+that is the ultimate statement of Darwinism and of Lamarckism on this
+doubtful question. Systematics is a mere catalogue, not at present
+only, but for ever, by the very nature of the organisms. It is not
+owing to the indefinite number of possible forms that both our theories
+came to deny the importance of systematics, but to the want of a *law*
+relating to this indefinite number: among chemical compounds indefinite
+possibilities also exist in some cases, but they obey the law of the
+general formula. It is very strange that Darwinians of all people are
+in the forefront of systematic research in all countries: do they not
+see that what they are trying to build up can only relate to accidental
+phenomena? Or have they some doubts about the foundations of their own
+theoretical views, in spite of the dogmatic air with which they defend
+them? Or is it the so-called historical interest which attracts them?
+
+A new question seems to arise at this point: Have not we ourselves
+neglected history in favour of systematics and laws? Our next lecture,
+the last of this year, will give the answer to this question.
+
+At present we continue our study of the possible aspects of systematics.
+It is not difficult to find out what meaning organic forms would assume
+under any phylogenetic theory opposed to the theories of contingency.
+It was their defence of contingency, that is, their lack of any law
+of forms, that caused these theories to be overthrown--reduced to
+absurdities even--and therefore, it follows that to assume any kind of
+transformistic law is at the same time to deny the accidental character
+of the forms of living beings.
+
+There is no *forma accidentalis*. Does that mean that the *forma
+essentialis* is introduced by this mere statement? And what would *that*
+assert about the character of systematics?
+
+
+THE ORGANIC FORM AND ENTELECHY
+
+This problem is not as simple as it might seem to be at the first
+glance, and, in fact, it is insoluble at present. It is here that the
+relation of the hypothetic transformistic principle to our concept of
+entelechy is concerned.
+
+We know that entelechy, though not material in itself, uses material
+means in each individual morphogenesis, handed down by the material
+continuity in inheritance. What then undergoes change in phylogeny,
+the means or the entelechy? And what would be the logical aspect of
+systematics in either case?
+
+Of course there would be a law in systematics in any case; and therefore
+systematics in any case would be rational in principle. But if the
+transformistic factor were connected with the means of morphogenesis,
+one could hardly say that specific form as such was a primary essence.
+Entelechy would be that essence, but entelechy in its generality and
+always remaining the same in its most intimate character, as the
+specific diversities would only be due to a something, which is not
+form, but simply means to form. But the *harmony* revealed to us in
+every typical morphogenesis, be it normal or be it regulatory, seems
+to forbid us to connect transformism with the means of morphogenesis.
+And therefore we shall close this discussion about the most problematic
+phenomena of biology with the declaration, that we regard it as more
+congruent to the general aspect of life to correlate the unknown
+principle concerned in descent with entelechy itself, and not with
+its means. Systematics of organisms therefore would be in fact
+systematics of entelechies, and therefore organic forms would be
+*formae essentiales*, entelechy being the very essence of form in its
+specificity. Of course systematics would then be able to assume a truly
+rational character at some future date: there might one day be found
+a principle to account for the totality of possible[160] forms, a
+principle based upon the analysis of entelechy.[161] As we have allowed
+that Lamarckism hypothetically explains congenital adaptedness in
+histology, and that Darwinism explains a few differences in quantity,
+and as such properties, of course, would both be of a contingent
+character, it follows that our future rational system would be combined
+with certain accidental diversities. And so it might be said to be
+one of the principal tasks of systematic biological science in the
+future to discover the really rational system among a given totality of
+diversities which cannot appear rational at the first glance, one sort
+of differences, so to speak, being superimposed upon the other.
+
+[160] The word “possible” relating to originating, of course, not to
+surviving. It is here that natural selection may acquire its logical
+importance alluded to above (see page 264).
+
+[161] The discussions in the second volume of this book will show the
+possible significance of such an analysis. We at present are dealing
+with entelechy in a quasi-popular manner.
+
+
+
+
+*C.* THE LOGIC OF HISTORY
+
+
+History, in the strictest sense of the word, is the enumeration of the
+things which have followed one another in order of time. History deals
+with the single, with regard both to time and space. Even if its facts
+are complex in themselves and proper to certain other kinds of human
+study, they are nevertheless regarded by history as single. Facts, we
+had better say, so far as they are regarded as single, are regarded
+historically, for what relates to specific time and space is called
+history.
+
+Taken as a simple enumeration or registration, history, of course,
+cannot claim to be a “science” unless we are prepared to denude that
+word of all specific meaning. But that would hardly be useful. As a
+matter of fact, what has actually claimed to be history, has always
+been more than a mere enumeration, even in biology proper. So-called
+phylogeny implies, as we have shown, that every one of its actual
+forms contains some rational elements. Phylogeny always rests on
+the assumption that only some of the characters of the organisms
+were changed in transformism and that what remained unchanged may be
+explained by the fact of inheritance.
+
+But this, remember, was the utmost we were able to say for phylogeny.
+It remains fantastic and for the most part unscientific in spite of
+this small degree of rationality, as to which it is generally not very
+clear itself. For nothing is known with regard to the positive factors
+of transformism, and we were only able to offer the discussion of a few
+possibilities in place of a real theory of the factors of descent.
+
+In spite of that it will not be without a certain logical value to begin
+our analysis of history in general by the discussion of possibilities
+again. Biology proper would hardly allow us to do more: for the
+simple “fact” of history is not even a “fact” in this science, but an
+hypothesis, albeit one of some probability.
+
+As discussions of mere possibilities should always rest on as broad a
+basis as possible, we shall begin our analysis by raising two general
+questions. To what kinds of realities may the concept of history
+reasonably be applied? And what different types of “history” would be
+possible *a priori*, if the word history is to signify more than a mere
+enumeration?
+
+
+1. THE POSSIBLE ASPECTS OF HISTORY
+
+Of course, we could select one definite volume in space and call all the
+consecutive stages which it goes through, its history: it then would be
+part of its history that a cloud was formed in it, or that a bird passed
+through it on the wing. But it would hardly be found very suggestive to
+write the history of space-volumes. In fact, it is to *bodies* in space
+that all history actually relates, at least indirectly, for even the
+history of sciences is in some respect the history of men or of books.
+It may suffice for our analysis to understand here the word body in its
+popular sense.
+
+Now in its relation to bodies history may have the three following
+aspects, as far as anything more than a simple enumeration comes into
+account. Firstly, it may relate to one and the same body, the term
+body again to be understood popularly. So it is when the individual
+history of the organism is traced from the egg to the adult, or when the
+history of a cloud or of an island or of a volcano is written. Secondly,
+the subject-matter of history may be formed by the single units of a
+consecutive series of bodies following each other periodically. To this
+variety of history the discoveries of Mendel and his followers would
+belong in the strictest sense, but so does our hypothetical phylogeny
+and a great part of the history of mankind. And lastly, there is a
+rather complicated kind of sequence of which the “history” has actually
+been written. History can refer to bodies which are in no direct
+relation with one another, but which are each the effect of another body
+that belongs to a consecutive series of body-units showing periodicity.
+This sounds rather complicated; but it is only the strict expression
+of what is perfectly familiar to you all. Our sentence indeed is
+simply part of the definition of a history of art or of literature for
+instance--or, say, of a phylogenetic history of the nests of birds. The
+single pictures are the subjects of the history of art, and nobody would
+deny that these pictures are the effects of their painters, and that
+the painters are individuals of mankind--that is, that they are bodies
+belonging to a consecutive series of body-units showing periodicity. Of
+course, it is only improperly that we speak of a history of pictures or
+of books or of nests. In fact, we are dealing with painters, and with
+men of letters or of science, and with certain birds, and therefore
+the third type of history may be reduced to the second. But it was not
+without value to pursue our logical discrimination as far as possible.
+
+So far we have always spoken of history as being more than a mere
+enumeration, but we have not ascertained what this “more” signifies. It
+is not very difficult to do so: in fact, there are three different types
+of history, each of a different degree of importance with respect to the
+understanding of reality.
+
+In the first place, history may start as a mere enumeration at the
+beginning, and at the end, in spite of all further endeavour, may
+*remain* that and nothing more. That may occur in the first as well
+as in the second group of our division of history with regard to
+its relation to bodies. Take a cloud and describe its history from
+the beginning to the end: there would never be much more than pure
+description. Or take one pair of dogs and describe them and their
+offspring for four generations or more: I doubt if you will get beyond
+mere descriptions in this case either. The only step beyond a mere
+enumeration which we can be said to have advanced in these instances,
+consists in the conviction, gained at the end of the analysis, that
+nothing more than such an enumeration is in any way *possible*.
+
+Quite the opposite happens when “history” deals with the individual
+from the egg to the adult: here the whole series of historical facts is
+seen to form one whole. This case therefore we shall call not history,
+but *evolution*, an evolving of something; the word “evolution” being
+understood here in a much wider sense than on former occasions,[162] and
+*including*, for instance, the embryological alternative “evolutio” or
+“epigenesis.”
+
+[162] See pp. 26, 45, 54, etc.
+
+And half-way between enumeration and evolution there now stands a type
+of history which is more than the one and less than the other: there is
+a kind of intelligible connection between the consecutive historical
+stages and yet the concept of a whole does not come in. The geological
+history of a mountain or of an island is a very clear instance of this
+class. It is easy to see here, how what *has been* always becomes the
+foundation of what *will be* in the *next* phase of the historical
+process. There is a sort of *cumulation* of consecutive phases, the
+later ones being impossible without the earlier. So we shall speak
+of the type of “historical cumulation” as standing between evolution
+and bare temporal sequence. By means of historical cumulations history
+may fairly claim to “explain” things. We “understand” a mountain or an
+island in all its actual characteristics, if we know its history. This
+“historical understanding” rests on the fact that what first appeared
+as an inconceivable complex has been resolved into a sequence of single
+events, each of which may claim to have been explained by actually
+existing sciences. The complex has been explained as being, though not
+a real “whole,” yet a sum of singularities, every element of which is
+familiar.
+
+But you may tell me that my discussion of evolution and of cumulation,
+as the higher aspects of history, is by no means complete; nay,
+more--that it is altogether wrong. You would certainly not be mistaken
+in calling my analysis incomplete. We have called one type of history
+evolution, the other cumulation; but how have these higher types been
+reached? Has historical enumeration itself, which was supposed to
+stand at the beginning of all analysis, or has “history” itself in its
+strictest sense, as relating to the single as such, risen unaided into
+something more than “history”? By no means: history has grown beyond
+its bounds by the aid of something from without. It is unhistorical
+elements that have brought us from mere history to more than history.
+We have created the concept of evolution, not from our knowledge of the
+single line of events attendant on a single egg of a frog, but from our
+knowledge that there are billions or more of frogs’ eggs, all destined
+to the same “history,” which therefore is not history at all. We have
+created the concept of cumulation not from the historical study of
+a single mountain, but from our knowledge of physics and chemistry
+and so-called dynamical geology: by the aid of these sciences we
+“understood” historically, and thus our understanding came from another
+source than history itself.
+
+
+2. PHYLOGENETIC POSSIBILITIES
+
+Does history always gain its importance from what it is not? Must
+history always lose its “historical” aspect, in order to become of
+importance to human knowledge? And can it *always* become “science” by
+such a transformation? We afterwards shall resume this discussion on
+a larger scale, but at present we shall apply what we have learned to
+hypothetic phylogeny. What then are the possibilities of phylogeny, to
+what class of history would it belong if it were complete? Of course, we
+shall not be able to answer this question fully; for phylogeny is *not*
+complete, and scarcely anything is known about the factors which act
+in it. But in spite of that, so much, it seems to me, is gained by our
+analysis of the possible aspects of history and of the factors possibly
+concerned in transformism, that we are at least able to formulate the
+possibilities of a phylogeny of the future in their strict logical
+outlines.
+
+Darwinism and Lamarckism, regarding organic forms as contingent, must
+at the same time regard organic history as a cumulation; they indeed
+*might* claim to furnish an historical explanation in the realm of
+biology--if only their statements were unimpeachable, which as we have
+seen, they are not.
+
+But any transformistic theory, which locates the very principle of
+phylogeny in the organism itself, and to which therefore even organic
+forms would be not accidental but essential, might be forced to regard
+the descent of organisms as a true evolution. The singularities in
+phylogenetic history would thus become links in one whole: history
+proper would become more than history. But I only say that phylogeny
+*might* be evolution, and in fact I cannot admit more than this *a
+priori*, even on the basis of an internal transformistic principle,
+as has been assumed. Such a principle also might lead always from one
+typical state of organisation to the next: but *ad infinitum*.[163]
+Then phylogeny, though containing what might in some sense be called
+“progress,” would not be “evolution”; it might even be called cumulation
+in such a case, in spite of the internal transforming principle, though,
+of course, cumulation from within would always mean something very
+different from cumulation from without.[164]
+
+[163] An immanent vitalistic phylogeny *without* a pre-established end
+has recently been advocated by H. Bergson (*L’évolution créatrice*,
+Paris, 1907).
+
+[164] In this connection the problem may be raised, whether there can be
+such a thing as unchangeable “species” in spite of the mutability of the
+individuals. Compare page 251, note 1.
+
+But we must leave this problem an open question, as long as our actual
+knowledge about transformism remains as poor as it is. We need only add,
+for the sake of logical interest, that phylogeny, as a true evolution,
+would necessarily be characterised by the possibility of being repeated.
+
+
+3. THE HISTORY OF MANKIND
+
+We only assume hypothetically that phylogeny has happened, and we know
+scarcely anything about the factors concerned in it. Now, it certainly
+would be of great importance, if at least in a small and definite field
+of biology we were able to state a little more, if the *mere fact* of
+phylogeny, of “history,” were at least beyond any doubt within a certain
+range of our biological experience. And indeed there is one department
+of knowledge, where history, as we know, *has happened*, and where we
+also know at least some of the factors concerned in it.
+
+I refer to the history of mankind; and I use the expression not at all
+in its anthropological or ethnographical sense, as you might expect
+from a biologist, but in its proper and common sense as the history of
+politics and of laws and of arts, of literature and of sciences: in a
+word, the history of civilisation. Here is the only field, where we know
+that there actually *are* historical facts: let us try to find out what
+these facts can teach us about their succession.
+
+The theory of history in this narrower meaning of the word has been
+the subject of very numerous controversies in the last twenty years,
+especially in Germany, and these controversies have led very deeply into
+the whole philosophical view of the universe. We shall try to treat our
+subject as impartially as possible.
+
+Hegel says, in the introduction to his *Phänomenologie des Geistes*:
+“*Die Philosophie muss sich hüten erbaulich sein zu wollen*”
+(“Philosophy must beware of trying to be edifying”). These words,
+indeed, ought to be inscribed on the lintel of the door that leads
+into historical methodology, for they have been sadly neglected by
+certain theoretical writers. Instead of analysing history in order to
+see what it would yield to philosophy, they have often made philosophy,
+especially moral philosophy, the starting-point of research, and history
+then has had to obey certain doctrines from the very beginning.
+
+We shall try as far as we can not to become “erbaulich” in our
+discussions. We want to learn from history for the purposes of
+philosophy, and we want to learn from history as from a phenomenon in
+time and in space, just as we have learnt from all the other phenomena
+regarding life in nature. Every class of phenomena of course may
+be studied with respect to generalities as well as with respect to
+particulars. The particular, it is true, has not taught us much in our
+studies so far. Perhaps it may be successful in the domain of history
+proper.
+
+If I take into consideration what the best authors of the last century
+have written about human history with respect to its general value, I
+cannot help feeling that none of them has succeeded in assigning to
+history a position where it would really prove to be of great importance
+for the aims of philosophical inquiry. Is that the fault of the authors
+or of human history? And what then would explain the general interest
+which almost every one takes, and which I myself take in history in
+spite of this unsatisfactory state of things?
+
+
+CUMULATIONS IN HUMAN HISTORY
+
+Let us begin our analytical studies of the value and the meaning of
+human history, by considering some opinions which deserve the foremost
+place in our discussion, not as being the first in time, but as being
+the first in simplicity. I refer to the views of men like Buckle, Taine,
+and Lamprecht, and especially Lamprecht, for he has tried the hardest to
+justify theoretically what he regards the only scientific aim of history
+to be. If we may make use of our logical scheme of the three possible
+aspects of history, it is clear from the beginning that the history of
+mankind, as understood by the three authors we have named, but most
+particularly by Lamprecht, is neither a mere enumeration nor a true
+evolution, but that it has to do with *cumulations*, in the clearest
+of their possible forms. The processes of civilisation among the
+different peoples are in fact to be compared logically with the origin
+of volcanoes or mountain-ranges in Japan, or in Italy, or in America,
+and show us a typical series of consecutive phases, as do these. There
+exists, for instance, in the sphere of any single civilisation an
+economic system, founded first on the exchange of natural products,
+and then on money. There are, or better, perhaps, there are said to
+be, characteristic phases succeeding one another in the arts, such as
+the “typical,” the “individualistic,” and the “subjective” phases. Any
+civilisation may be said to have its “middle ages,” and so on. All these
+are “laws” of course in the meaning of “rules” only, for they are far
+from being elemental, they are not “principles” in any sense. And there
+are other sorts of “rules” at work for exceptional cases: revolutions
+have their rules, and imperialism, for instance, has its rules also.
+
+Now, as the consecutive phases of history have been shown to be
+true cumulations, it follows that the rules which are revealed by
+our analysis, are rules relating to the very origin of cumulations
+also. The real *element* upon which the cumulation-phases, and the
+cumulation-rules together rest, is the human individual as the bearer
+of its psychology. Nobody, it seems to me, has shown more clearly than
+Simmel that it is the human individual, *qua* individual, which is
+concerned in *every* kind of history.
+
+History, viewed as a series of cumulations, may in fact claim to
+satisfy the intellect by “explaining” a good deal of historical facts.
+It explains by means of the elemental factor of individual psychology,
+which every one knows from himself, and by the simple concept that there
+is a cumulation, supported by language and by writing as its principal
+factors, which both of course rest on psychology again. Psychology,
+so we may say, is capable of leading to cumulation phenomena; the
+cumulations in history are such that we are able to understand them by
+our everyday psychology; and history, so far as it is of scientific
+value, consists exclusively of cumulations.
+
+No doubt there is much truth in such a conception of history; but
+no doubt also, it puts history in the second rank as compared with
+psychology; just as geology stands in the second rank as compared with
+chemistry or physics. Geology and human history may lead to generalities
+in the form of rules, but these rules are *known* to be not elemental
+but only cumulative; and moreover, we know the elements concerned in
+them. The elements, therefore, are the real subjects for further studies
+in the realm of philosophy, but not the cumulations, not the rules,
+which are known to be due to accidental constellations. Of course, the
+“single” is the immediate subject of this sort of history, but the
+single as such is emphatically pronounced to be insignificant, and the
+cumulations and the cumulative rules, though “singles” in a higher sense
+of the word, are shown to be anything but elementalities.
+
+Therefore, on a conception of human history such as that of Buckle,
+Taine, Lamprecht, and others, we, of course, ought to take an interest
+in history, because what is “explained” by historical research touches
+all of us most personally every day and every year. But our philosophy,
+our view of the world, would remain the same without history as it is
+with it. We only study history, and especially the history of our own
+civilisation, because it is a field of actuality which directly relates
+to ourselves, just as we study for practical purposes the railway
+time-tables of our own country, but not of Australia; just as we study
+the local time-table in particular.
+
+If the mere *rerum cognoscere causas* is regarded as the criterium of
+science, history of Lamprecht’s type of course is a science, for its
+explanations rest upon the demonstration of the typical constellations
+and of the elemental factor or law from which together the next
+constellations are known necessarily to follow. But history of this kind
+is not a science in the sense of discovering *den ruhenden Pol in der
+Erscheinungen Flucht*.
+
+
+HUMAN HISTORY NOT AN “EVOLUTION”
+
+Quite another view of history has been maintained by Hegel, if his
+explanations about the *Entwicklung des objectiven Geistes* (“the
+development of the objective mind”) may be co-ordinated with our
+strictly logical categories of the possible aspects of history. But I
+believe we are entitled to say that it was a real *evolution* of mankind
+that Hegel was thinking of; an evolution regarding mankind as spiritual
+beings and having an end, at least ideally. One psychical state was
+considered by Hegel to generate the next, not as a mere cumulation
+of elemental stages, but in such a way that each of the states would
+represent an elementality and an irreducibility in itself; and he
+assumed that there was a continuous series of such stages of the mind
+through the course of generations. Is there any sufficient reason in
+historical facts for such an assumption?
+
+The mind “evolves” itself from error to truth by what might be called
+a system of contradictions, according to Hegel, with respect to logic
+as well as to morality; the sum of such contradictions becoming smaller
+and less complicated with every single step of this evolution. No doubt
+there really occurs a process of logical and moral refining, so to say,
+in the individual, and no doubt also, the results of this process,
+as far as attained, can be handed down to the next generation by the
+spoken word or by books. But it is by no means clear, I think, that this
+process is of the type of a real evolution towards an end, so far as it
+relates to the actual series of generations as such. On the contrary,
+it seems to me that we have here simply what we meet everywhere in
+history--a sort of cumulation resting upon a psychological basis.
+
+The dissatisfaction that exists at any actual stage of contradiction,
+both moral and logical, is one of the psychical factors concerned;
+the faculty of reasoning is the other. Now it is a consequence of the
+reasoning faculty that the dissatisfaction continually decreases, or
+at least changes in such a way that each partial result of the logical
+process brings with it the statement of new problems. The number of
+such problems may become less, as the logical process advances, and,
+indeed, there is an ideal state, both logical and moral, in which there
+are no more problems, but only results, though this ideal could hardly
+be regarded as attainable by the *human* mind. In the history of those
+sciences which are wholly or chiefly of the *a priori* type, this
+process of deliverance from contradictions is most advantageously to
+be seen. It is obvious in mechanics and thermodynamics, and the theory
+of matter is another very good instance. A certain result is reached;
+much seems to be gained, but suddenly another group of facts presents
+itself, which had been previously unknown or neglected. The first result
+has to be changed or enlarged; many problems of the second order arise;
+there are contradictions among them, which disappear after a certain
+alteration of what was the first fundamental result, and so on. And the
+same is true about morality, though the difficulties are much greater
+here, as a clear and well-marked standard of measurement of what is good
+and what is bad, is wanting, or at least, is not conceded unanimously.
+But even here there is a consensus on some matters: one would hardly go
+back to slavery again, for instance, and there are still other points
+in morality which are claimed as ideals at least by a great majority of
+moral thinkers.
+
+But all this is not true “evolution,” and indeed, I doubt if such an
+evolution of mankind could be proved at present in the sense in which
+Hegel thought it possible. The process of logical and moral deliverance
+from contradictions *might* come to an end in *one* individual; at least
+that is a logical possibility, or it might come to an end in, say,
+six or ten generations. And there is, unfortunately for mankind, no
+guarantee that the result will not be lost again and have to be acquired
+a second time. All this proves that what Hegel regarded as an evolution
+of the race is only a cumulation. There is nothing evolutionary relating
+to the generations of mankind as such. At least, nothing is proved about
+such an evolution.[165]
+
+[165] On account of the limited size of the earth a certain final stage
+of human civilisation might be expected in a future time; but it would
+be the size of the earth which determined this end, and not the process
+of civilisation itself.
+
+You may call my view pessimistic, and indeed you may be right so far
+as the sum total of human beings as such is in question. But, be it
+pessimistic or not, we are here moving on scientific ground only, and
+have merely to study the probability or improbability of problematic
+facts, and with such a view in our mind, we are bound to say that a
+true logical and moral evolution of mankind is not at all supported
+by known facts. There is a process of logical and moral perfection,
+but this process is *not one*, is not “single” in its actuality; it is
+not connected with the one and single line of history, but only with a
+few generations each time it occurs, or even with one individual, at
+least ideally. And this process is not less a process of cumulation
+than any other sort of development or so-called “progress” in history
+is. Philosophers of the Middle Ages, in fact, sometimes regarded human
+history as *one* evolutionary unity, beginning with the Creation and
+ending with the Day of Judgment; but every one must agree, I think,
+that even under the dogmatic assumptions of orthodoxy history would by
+no means *necessarily* be an “evolution.” Even then the paths taken by
+different individuals or different branches of the human race on their
+way to redemption *can* be regarded as independent lines.
+
+Thus Hegel’s conception of an evolution of mankind, it seems to me,
+fails to stand criticism. By emphasising that there are certain lines of
+development in history which bring with them a stimulus to perfection,
+and that these lines relate to all that is highest in culture, Hegel
+certainly rendered the most important service to the theory of history;
+but in spite of that he has revealed to us only a special and typical
+kind of cumulation process, and nothing like an evolution. We may say
+that the very essence of history lies in this sort of cumulation, in
+this “pseudo-evolution” as we might say; and if we like to become moral
+metaphysicians we might add, that it is for the sake of the possibility
+of this sort of cumulation that man lives his earthly life; the Hindoos
+say so, indeed, and so do many Christians. But even if we were to depart
+from our scientific basis in this way we should not get beyond the realm
+of cumulations.
+
+All this, of course, is not to be understood to affirm that there never
+*will* be discovered any real evolutionary element in human history--in
+the so-called “subconscious” sphere perhaps--but at present we
+certainly are ignorant of such an element.
+
+
+THE PROBLEM OF THE “SINGLE” AS SUCH
+
+If history has failed to appear as a true evolution, and if, on the
+other hand, it reveals to us a great sum of different cumulations, some
+of very great importance, others of minor importance, what then remains
+of the importance of the single historical event in its very singleness?
+What importance can the description of this event have with regard to
+our scientific aims? We could hardly say at present that it appears to
+be of very much importance at all. The historical process as a whole
+has proved to be not a real elemental unit, as far as we know, and such
+elemental units as there are in it have proved to be of importance only
+*for* individual psychology but not *as* history. History has offered
+us only instances of what every psychologist knew already from his own
+experience, or at least might have known if he had conceived his task in
+the widest possible spirit.
+
+But is no other way left by which true history might show its real
+importance in spite of all our former analysis? Can history be saved
+perhaps to philosophical science by any new sort of reasoning which we
+have not yet applied to it here.
+
+As a matter of fact, such new reasoning has been tried, and
+Rickert,[166] in particular, has laid much stress upon the point
+that natural sciences have to do with generalities, while historical
+sciences have to do with the single in its singleness only, and, in
+spite of that, are of the highest philosophical importance. He does not
+think very highly of so-called “historical laws,” which must be mere
+borrowings from psychology or biology, applied to history proper, and
+not touching its character as “history.” We agree with these statements
+to a considerable extent. But what then about “history proper,” what
+about “the single in its very singleness”?
+
+[166] *Die Grenzen der naturwissenschaftlichen Begriffsbildung*,
+Tübingen and Leipzig, 1902.
+
+Let us say at first a few words about this term “single” so very often
+applied by us. In the ultimate meaning of the word, of course, the
+series of actual sensations or “presentations” is the “single” which is
+given “historically” to each individual, and therefore to the writer of
+history also, and in fact, history as understood by Rickert is based
+to a great extent upon this primordial meaning of single “givenness.”
+The word “single,” in his opinion, relates to the *actual and true
+specification* of any event, or group of events, at a given time and
+at a given locality in space, these events possessing an identity of
+their own and never being repeated without change of identity. If the
+subject-matter of history is defined like this, then there are, indeed,
+“Grenzen der naturwissenschaftlichen Begriffsbildung” with regard to
+history, for natural sciences have nothing to do with the single in such
+an understanding of the word.
+
+Rickert says somewhere that history as a real evolution, as one
+totality of a higher order, would cease to be proper history: and he
+is right. History, in fact, would soon lose the character of specific
+attachment to a given space and to a given time, and would lose its
+“non-repeatability,” in the logical sense at least, if it were one
+*unit* in reality: as soon as it was that, it would have become a
+logical generality, an element in nature, so to say, in spite of its
+factual singularity. But history is not obliged to become that, Rickert
+states; and we may add that history in fact cannot become that, because
+it simply proves not to be an evolution as far as we know at present.
+
+But what importance does Rickert attach to his history specified and
+non-repeatably single?
+
+History has a logic of its own, he says; the scheme of its logic is not
+the syllogism, but the *relation to “values.”* So far as the single
+historical facts can be related to values, they are of historical
+importance, and in such a way only does history in its proper sense
+become important in itself and through itself at the same time. Must
+history always lose its historical aspect to become of importance to
+human knowledge? That is the question we asked whilst considering the
+general logical types of the “evolution” and “cumulation” that arose out
+of the analysis of the historical facts of problematic phylogeny. It
+now might seem that this question may be answered, and that it may be
+answered by a clear and simple “No.” The history of mankind, according
+to Rickert, seems to be important in itself, and without borrowing from
+any other branch of study. But is his reasoning altogether cogent and
+convincing?
+
+Has it really been able to attribute to history in the strictest sense
+such an importance for philosophy, for the theory of the universe, “für
+die Weltanschauung,” that history proper may in fact be allowed to take
+its place beside science proper?
+
+The relation to values is not to include any kind of “Bewertung” of
+judgment, Rickert allows. In fact, history of any kind would hardly
+satisfy the reader, if moral judgment were its basis. Every reader, of
+course, has a moral judgment of his own, but, unfortunately, almost
+every reader’s judgment is different from his neighbour’s, and there
+is no uniformity of moral principles as there is of geometrical ones.
+We shall come back to this point. At present we only state the fact
+that indeed moral judgment can never be the foundation of history, and
+that Rickert was very right to say so: it is enough to put the names
+of Tolstoy and Nietzsche together to understand how devoid of even
+the smallest general validity would be a history resting upon moral
+principles.
+
+But what then are the “values” of Rickert to which history has to
+relate, if moral values in their proper sense have to be excluded? It is
+here that his discussions begin to become obscure and unsatisfactory,
+and the reason is fairly intelligible. He is trying to prove the
+impossible; he wants to put history beside science in its real
+philosophical importance, in spite of the fact that all evidence to
+establish this is wanting.
+
+These “values,” to which every historical act in its singularity has to
+be related in order to become an element of real history, are they after
+all nothing but those groups of the products of civilisation which in
+fact absorb the interest of men? Is it to groups of cultural phenomena,
+such as arts, science, the State, religion, war, economics, and so on,
+that “historical” facts have to be related? Yes, as far as I understand
+our author, it is simply to these or other even less important groups
+of cultural effects--cultural “cumulations,” to apply our term--that a
+single action of a man or a group of men must bear some relation in
+order to become important historically.
+
+But what does that mean? Is the relation to such “values” to be
+regarded as really rendering history equal to the sciences of nature in
+philosophical importance?
+
+In the first place, there is no more agreement about such “values” than
+there is in the field of morals. Imagine, for instance, a religious
+enthusiast or recluse writing history! I fancy there would be very
+little mention of warriors and politicians: war and politics would
+not be “values” in *any* sense to such a man. And we know that there
+are others to whom those products of civilised life rank amongst the
+first. Rickert well notes that there is one great objection to his
+doctrine--the character of universality[167] is wanting to his history,
+or rather to the values forming its basis; for there cannot be, or at
+least there actually is not at present, a *consensus omnium* with regard
+to these “values.”
+
+[167] The word “universality” to be understood here in quite an
+unpretentious quasi-popular meaning, not strictly epistemologically.
+
+I am convinced that Rickert is right in his conception of real “history”
+as the knowledge of the single acts of mankind. But this conception
+proves just the contrary of what Rickert hoped to prove; for history in
+this sense is moulded by the actual products of culture, that is, by
+the effects which actually exist as groups of cultural processes, and
+it cannot be moulded by anything else; the historian correlates history
+with what *interests* him personally.
+
+Here now we have met definitively the ambiguous word: history indeed
+is to end in “interest” and in being “interesting.” There is nothing
+like a real “value” in any sense underlying history; the word *value*
+therefore would better give place to the term “centre of interest”--a
+collection of stamps may be such a “centre.” History, then, as the
+knowledge of cultural singularities, is “interesting,” and its aspects
+change with the interests of the person who writes history: there is no
+commonly accepted foundation of history.[168]
+
+[168] To avoid mistakes I wish to say here most emphatically that,
+according to Rickert, the method of history is regarded as completely
+*free* from subjectivity as soon as its “values” are once *established*.
+But this cannot avail to save the theory.
+
+And it follows that history as regarded by Rickert cannot serve as
+the preliminary to philosophy. It *may* be[169] of use for personal
+edification or for practical life: granting that the “centres of
+interest” as referred to are of any real ethical or at least factual
+importance. But you may take away from history even the greatest
+personalities, and your view of the universe, your philosophy, would
+remain the same, except of course so far as these personalities
+themselves have contributed to philosophy in any way.
+
+[169] This is a rather optimistic conception of “history.” Personally, I
+must confess that even its emotional and practical importance seems to
+me to be at least diminished by the retarding effects which all sorts
+of “historical” considerations--in science as well as in arts and in
+public life--carry with them. All real progress is non-historical--and
+its champions almost always have become martyrs: this fact seems not to
+recommend history as a means of education, except for persons of a very
+strong character.
+
+Now, on the other hand, it is worth noticing that, even if there were
+generally accepted “values,” history as the doctrine of singularities
+would be deprived of philosophical importance. Its single cases would
+then be merely *instances* of certain types of actions and occurrences
+which have been proved to be “valuable,” *i.e.* to be centres of
+interest, before-hand. Rickert has observed that the relation to
+any judgments about moral values would render history unhistorical,
+for the generalities to which it is related would be the main thing
+in such a case. But he did not notice, as far as I can see, that
+history, if related to *any* “values” whatever--if there were any
+generally conceded--would become “non-historical” just as well: for the
+*generalities* as expressed in the “values” would be the main thing in
+this case also. In fact, there is no escape from the dilemma:--either no
+general centres of interest, and therefore a mere subjective “history”;
+or general “values,” and therefore history a mere collection of
+instances.
+
+The “limits of concepts in natural sciences” then are the same as the
+limits of *intellectual* concepts in general. For intellectual, *i.e.*
+logical, “values” are the only centres of interest that can lay claim
+to universality. There are indeed other groups of important concepts,
+the ethical ones, but they are outside intellectuality and may enter
+philosophy only as problems, not as solutions. Therefore, history in
+its true sense, even if related to the ethical group of concepts,
+has no bearing on philosophy. Philosophically it remains a sum of
+contingencies, in which certain laws of cumulation and certain series of
+cumulation may be discovered. But these series and these laws, if taken
+scientifically, only offer us instances of psychological elementalities.
+They also might be instances of primary ethical states and relations, if
+there were such relations of more than a mere subjective and personal
+validity, which at present at least seems not to be the case.
+
+
+
+
+CONCLUSIONS ABOUT SYSTEMATICS AND HISTORY IN GENERAL
+
+
+We have finished our analysis of the history of mankind as the only
+instance of an historical biological process that is actually known to
+exist and is not only assumed hypothetically.
+
+What we have learnt from this analysis, though certainly important in
+itself, has not afforded us any new result for theoretical biology.
+
+The history of mankind is proved to be of philosophical importance,
+at present, so far only as it offers instances to the science of
+psychology; besides that it may be of value and importance to many
+conditions of practical and emotional life.
+
+There is only one science, and only one kind of logic too. “In one sense
+the only science”--that was the predicate attached to natural sciences
+by Lord Gifford, as you will remember from our first lecture. It is not
+without interest to note that at the end of our course of this year,
+we find occasion to realise on what a deep insight into logical and
+philosophical relations that sentence was grounded.
+
+We now leave the theory of human history, which has been to us nothing
+more than a branch of biological phylogeny in general. We have dealt
+with it from quite a simple realistic point of view, not burdened by any
+epistemology. We have taken psychical states as realities, just as we
+have taken as realities all parts of the animal body; and it seems to
+me that we were entitled to do so, as it was only history *about* the
+actions of men we were dealing with, not their actions themselves. Next
+summer we shall begin with studying action as action, and then, in fact,
+a well-founded epistemology will be among our first requirements. And
+history also will come on the scene once more.
+
+It is the main result of our last chapters, devoted to systematics,
+transformism, and human history in particular, that no conclusions
+really useful for further philosophical discussion can at present be
+gained from these topics; there either is too little actual knowledge,
+or there are only combinations of natural elementalities, but no
+elementalities of any new kind.
+
+To sum up: we expected that a rational system might be a biological
+result of the future, but we could not claim at all to possess such a
+system. We said that transformism might be proved one day to be a true
+evolution, governed by one immanent principle, which then would have to
+be regarded as a new primary factor in nature, but we did not know the
+least about that principle.
+
+Human history, on the other hand--that is, the only historical process
+concerned with life that is actually known to have occurred--could not
+teach us anything of an elemental character, since human history, at
+present at least, did not appear to us as a true evolution, but only as
+a sum of cumulations, and the singularities of this history, taken by
+themselves, could only be of practical or emotional interest.
+
+Thus it is from the study of the living *individual* only, that we
+have so far gained elemental principles in biology. The analysis of
+individual morphogenesis and of individual inheritance has yielded
+us the concept of entelechy as the chief result of the first part of
+our lectures. We shall be able to get more proofs of the autonomy of
+the individual life in the beginning of the second part; indeed, the
+beginning of that part will bring us to a full understanding of what the
+living individual is, and what it is not. And then the real philosophy
+of life, that is, the philosophy of the individual, will occupy us for
+the greater half of our lectures of next summer.
+
+
+
+
+INDEX
+
+
+ Absolute, 5
+
+ Acclimatisation, 191
+
+ Acquired characters, 217, 276 f.
+
+ Adaptation (definition), 166, 171, 185
+ to changes from without, 172 ff.
+ functional, 114, 176 ff.
+ and Lamarckism, 272, 280
+ mechanical, 177 f.
+ morphological, 168 ff.
+ physiological, 184 ff.
+ primary and secondary, 188 f.
+
+ Adaptedness, 186 f.
+
+ *Adiantum*, 279
+
+ Adventitious, 55, 74, 111, 221
+
+ Albumen, 200
+
+ Allelomorphs, 231
+
+ Amphibious plants, 172 ff.
+
+ Annelids, 65, 70, 221
+
+ Answering reaction, 181
+
+ Anti-bodies, 206 f.
+
+ Antitoxins, 207 f.
+
+ *A priori*, 6
+
+ Aristotle, 144
+
+ *Ascaris*, 93
+
+ *Aspergillus*, 195
+
+ Assimilation, 17
+
+ Atrophy, 178
+
+ Autonomy of life, 143, 224 f., 324
+
+
+ Babák, 177
+
+ Baer, C. E. v., 48 f. 282
+
+ Bateson, 229 ff., 238
+
+ Bayliss, 204, 212
+
+ *Begonia*, 221
+
+ Bergson, 305
+
+ Berkeley, 6
+
+ Berthold, 91
+
+ Biogenetisches Grundgesetz, 248
+
+ Biology, 8 ff., 15 f.
+
+ Blaringhem, 238, 276
+
+ Blastoderm, 39
+
+ Blastomeres, 36, 59, 61 f., 79
+
+ Blastula, 37, 61, 79
+
+ Blumenbach, 26
+
+ Boirivant, 174
+
+ Bonnet, 26
+
+ Boveri, 29, 60, 95, 235 f.
+
+ Buckle, 308, 310
+
+ Bunge, v., 248
+
+ Bütschli, 91
+
+
+ Calcium, 97
+
+ Calkins, 33
+
+ Cambium, 120, 183, 220
+
+ Catalysis, 164, 203
+
+ Categories, 6 f.
+
+ Cause, 99 ff.
+
+ Cell, 27 f.
+ -division, 28 ff., 53, 94
+ -lineage, 58, 70
+ -theory, 27 f.
+
+ Chemical theory (of morphogenesis), 134 ff.
+
+ Chemistry, systematics of, 244.
+
+ Child, C. M., 180
+
+ Chromatic regulations, 197
+
+ Chromatin, 28 f.
+
+ Chromosomes, 30, 237
+
+ Chun, 66
+
+ Classification, 246 f.
+
+ *Clavellina*, 129, 154, 162 f.
+
+ Cleavage, 35 ff., 53, 58, 60, 63, 71, 92
+
+ Colloids, 187
+
+ Compensatory process, 112
+
+ Complex potencies, 112, 120
+
+ Conic sections, 243
+
+ Conjugation, 33
+
+ Conklin, 86
+
+ Contingency, 218, 284 ff. 304
+
+ Continuity of germ-plasm, 215, 227
+
+ Cope, 273
+
+ Correlation (of masses), 93
+ (of parts), 247
+
+ Correns, 228
+
+ Crampton, 70 f.
+
+ Crayfish, 105
+
+ Ctenophores, 66
+
+ Cumulation, 301 ff., 308 ff., 314, 317
+
+ Cuvier, 247
+
+
+ Darwin, Ch., 260 ff., 271, 283
+
+ Darwinism, 260 ff., 271, 283 ff., 293 ff., 304
+
+ Davenport, 191, 206
+
+ Delage, 32
+
+ Descent, theory of, 250 ff.
+
+ Description, 12, 50
+
+ Detto, 172
+
+ Directive stimuli, 102 ff.
+
+ Doncaster, 232
+
+ Dreyer, 92
+
+
+ *Echinus*, 27, 33 ff., 60 ff., 68, 81, 85, 87,
+ 98, 104, 108, 111, 154, 232, 235
+
+ Ectoderm, 41, 81, 122
+
+ Egg, 31, 33 f.
+
+ Ehrlich, 207 f.
+
+ Eimer, 292
+
+ Elementary organs, 46 ff.
+ processes, 46 ff.
+
+ Elements of nature, 9
+
+ Embryo, 44
+ frog’s, 59, 65, 67
+ half, 59, 61, 66 ff.
+ whole, 61, 67 f.
+
+ Endoderm, 41, 81
+
+ Entelechy, 143 f., 224 f., 295
+
+ Entwickelungsmechanik, 57, 70, 78, 241
+
+ Enumeration, 297, 300
+
+ Enzymes, 164, 203
+
+ Epigenesis, 26, 45, 54, 72, 144, 301
+
+ Equifinality (of restitutions), 159 f.
+
+ Equipotential, 83
+
+ Eschenhagen, 195
+
+ Evolutio, 26, 45 f., 54, 59, 61, 64, 72, 144, 205, 301
+
+ Evolution, 8, 21, 46, 250, 301, 305, 311 ff., 317
+
+ Experience, 7 f., 12, 212
+
+ Experiment, 51, 56 f.
+
+ “Explaining,” 51, 309
+
+ Explicit potency, 84
+
+
+ Fasting, 199 f.
+
+ Ferments, 164, 203 f.
+
+ Fertilisation, 32 ff.
+
+ Fischer, 278
+
+ Foges, 107
+
+ Form, closed or open, 49
+
+ Form, organic, specific, 16 ff., 25, 92, 293 ff.
+
+ Forma accidentalis, 293
+ essentialis, 294 f.
+
+ Formative stimuli, 102 ff., 113, 118, 133
+
+ Francé, 158, 239
+
+ Frédéricq, 196
+
+ Frog, embryo of, 59, 65, 67
+
+ Fromm, 205
+
+ Function (mathematical), 80
+
+ Fungi, metabolism of, 201
+
+
+ Gaidukow, 197 f.
+
+ Galls, 101
+
+ Galton, 228, 238
+
+ Gamble and Keeble, 198
+
+ Gastrula, 41, 61, 81
+
+ Gautier, 239
+
+ Geographical distribution, 251 f.
+
+ Geometry, solid, 243
+
+ Germ-layers, 41, 44, 61
+ -lineage, 215
+ -plasm, 52, 215
+
+ Gifford, Lord, 1 ff., 322
+
+ Godlewski, 105, 155, 235
+
+ Goebel, 116
+
+ Goethe, 247
+
+ Goette, 48, 56, 214
+
+ Goltz, 181
+
+ Growth, 30, 93 f.
+
+ Gruber, 236
+
+
+ Haeckel, 37, 41
+
+ Half-embryo, 59, 61, 66 ff.
+
+ Haller, A. v., 26
+
+ Harmony, 107 ff., 117, 295
+
+ Hausmann, 206
+
+ Heat production, 193
+
+ Hegel, 307, 311 ff.
+
+ Herbst, 96 ff., 102, 104 ff., 172, 177, 200, 232, 236
+
+ Heredity, 21, 52
+
+ Hering, 216 f.
+
+ Hertwig, O., 60, 65
+
+ Hertwig, R., 32 f., 60, 107
+
+ His, 56, 93
+
+ History, 2, 14, 21, 250, 257, 297 ff.
+ of mankind, 306 ff.
+
+ Holmes, 180
+
+ Hume, 6
+
+ Hypertrophy, 112, 114
+
+ Hypertypy, 112
+
+
+ Idealism, 5, 7
+
+ Immunity, 204 ff.
+
+ Implicit potency, 84
+
+ Improvement (of morphogenesis), 212
+
+ Indifferent cells, 182
+
+ Inflammation, 206
+
+ Inheritance, 35, 214 ff.
+ of acquired characters, 217, 275 ff., 290
+
+ Irritability, 190 ff.
+
+
+ Jacoby, 207
+
+ Jaeger, 214
+
+ Jennings, 218
+
+
+ Kammerer, 176, 280
+
+ Kant, 6 f.
+
+ Kirchhoff, 50
+
+ Klebs, 96, 170, 180, 238, 276
+
+ Kölliker, 292
+
+ Korshinsky, 239
+
+ Krašan, 221, 251
+
+
+ Lamarck, 271 f., 291
+
+ Lamarckism, 271 f., 284 ff., 293 ff., 304
+
+ Lamprecht, 308, 310
+
+ Larva, 41 f., 44
+
+ Law of nature, 13, 16
+
+ Leibniz, 6
+
+ Lens (of eye), 105, 221
+
+ Liebmann, 256
+
+ Life, 9 f., 16, 21
+
+ Lillie, R. S., 236
+
+ Limits of regulability, 212
+
+ Lithium, 99
+
+ “Living,” 9, 16
+
+ Localisation, 101, 103, 118 ff.
+
+ Locke, 6
+
+ Loeb, J., 32, 102, 164, 179, 196, 236
+
+ Loeb, L., 208
+
+ Lyon, 87
+
+
+ MacDougal, 238 f., 276
+
+ Machine (definition), 139
+
+ Machine-theory of life, 138 ff., 187, 210
+
+ Maillard, 196
+
+ Manifoldness, 25 f., 30, 45
+ intensive, 144
+
+ Materialism, 283
+
+ Materials, transport of, 194
+
+ Matter, theory of, 8
+
+ Maturation, 31, 87
+
+ Mayenburg, v., 195
+
+ Means, of morphogenesis, 89 ff., 101, 113, 118, 228, 234
+
+ Memory, 216 f.
+
+ Mendel, 229 f.
+
+ Merrifield, 198
+
+ Mesenchyme, 39, 41, 104, 111, 151 f.
+
+ Metabolic regulations, 198 f.
+
+ Metabolism, 16, 184
+ of fungi, 201
+
+ Metschnikoff, 206
+
+ Micromeres, 36, 60
+
+ Miehe, 116
+
+ Mill, J. S., 57
+
+ *Mimosa*, 191
+
+ Minkiewicz, 198
+
+ Modification, 277
+
+ Molluscs, 70 f., 86
+
+ Morgan, T. H., 32, 66 f., 95, 107, 114 f., 162, 230
+
+ Morphaesthesia, 157
+
+ Morphogenesis, 20, 52, 76, 112, 118 f.
+
+ Morphology, 12
+
+ Movements, organic, 17
+
+ Mutations, 237 f., 276, 291
+
+
+ Nägeli, 266, 292
+
+ Nathansohn, 196
+
+ Natural selection, 261 f., 290
+
+ Nature, 5 ff.
+
+ Němec, 116
+
+ Newport, 57
+
+ Newt (regeneration of), 155, 221 f.
+
+ Noll, 146, 157 f.
+
+ Nomothetic, 14 f.
+
+ Normal, 78
+
+ Nuclear division, 28 f., 62, 64 f., 72, 235
+
+ Nucleus, 28, 35
+ rôle of nucleus in inheritance, 233 f.
+
+
+ Organ-forming substances, 117
+
+ *Oscillariae*, 197
+
+ Osmotic pressure, 93, 187, 194 f.
+
+ Overton, 196 f.
+
+ Oxidation, rôle of, 198 f.
+
+
+ Palaeontology, 252
+
+ Parallelism (psycho-physical), 146
+
+ Parthenogenesis, 32
+
+ Pauly, 146, 217, 273 f.
+
+ Pawlow, 204, 210, 212
+
+ Pearl, R., 212
+
+ Pfeffer, 195, 201
+
+ Phagocytosis, 206
+
+ Phenomenon, 5 f.
+
+ Philosophy, natural, 4
+ of nature, 4, 7, 9
+ of the organism, 9, 15
+
+ Phylogeny, 255, 291, 297, 304 ff.
+
+ Physiology, 12
+ of development (morphogenesis), 20
+
+ *Planaria*, 130, 155, 162 f., 200
+
+ Plants, 48 f.
+
+ Plato, 2
+
+ Pluteus, 42
+
+ Poisons, 205 ff.
+
+ Pole, 36
+
+ Polarity, 106
+
+ Potencies, complex, 112, 120
+ explicit, 84
+ implicit, 84
+ primary, 84, 111
+ prospective, 77 ff., 83, 89, 118, 125, 241
+ secondary, 84, 110
+
+ Poulton, 198
+
+ Precipitin, 207 f.
+
+ Pressure experiments, 63, 141
+
+ Primary potency, 84, 111
+ purposefulness, 146, 287
+ regulation, 85, 174, 188
+
+ Progress, 305
+
+ Pronuclei, 55
+
+ Prospective potency, 77 ff., 83, 89, 118, 125, 241
+ value, 77 f., 80, 122
+
+ Protista (Protozoa), 27, 130, 236
+
+ Protoplasm, 28, 30
+ morphogenetic rôle of, 67
+
+ Przibram, 112, 248
+
+
+ Rádl, 247
+
+ Rauber, 235
+
+ Reaction, answering, 181
+
+ Reciprocity of harmony, 156 f.
+
+ Re-differentiation, 75, 111, 163
+
+ Regeneration, 55, 74, 105, 111, 221
+ super-, 115 f.
+
+ Regulation, 68, 73, 85, 111, 165
+ defined, 166
+ metabolic, 198 f.
+ secondary, 85, 165, 188
+
+ Reinke, 146
+
+ Restitution, 21, 74, 110, 112 ff.
+ defined, 166
+ and Darwinism, 267
+ and Lamarckism, 286
+ of second order, 158
+
+ Retina, 191
+
+ Retro-differentiation, 163 f.
+
+ Rhumbler, 93
+
+ Ribbert, 114
+
+ Rickert, 315 ff.
+
+ Roux, 26, 48, 55 ff., 66 f., 76, 89, 92 f., 108, 161, 176 f., 241
+
+ Rubner, 193
+
+
+ Sachs, 117
+
+ Sadebeck, 279
+
+ *Salamandra*, 175, 281
+
+ Schneider, 146
+
+ Schultz, E., 200
+
+ Schultze, O., 67
+
+ Schwendener, 177
+
+ Science, 14, 297
+ natural, 1 ff.
+ rational, 12
+
+ Sea-urchin, *see* Echinus
+
+ Secondary potency, 84, 110
+ regulation, 85, 165, 188
+
+ Secretion, internal, 116, 200
+
+ Segmentation, 35
+
+ Selective qualities (of tissues), 186
+
+ Self-differentiation, 108
+
+ Semon, 216 f.
+
+ Sex, 107
+
+ Single, the, 315 ff.
+
+ Skeleton, 40 ff., 44, 47, 92
+
+ Spemann, 105
+
+ Spermatozoon (spermia), 32 ff.
+
+ Splitting (of hybrids), 229 f.
+
+ Stahl, 197
+
+ Standfuss, 278
+
+ Starfish, 44, 81, 122
+
+ Starling, E., 116, 204, 212
+
+ *Stentor*, 131
+
+ Stimuli, directive, 102 ff.
+ formative, 102 ff., 113, 118, 133
+ of restitutions, 113 f.
+
+ Structure of protoplasm, 66, 69, 72 f. 85, 88
+
+ Substance, living, 17
+
+ Sumner, 196
+
+ Super-regeneration, 115 f.
+
+ Surface-tension, 91
+
+ Sutton, 230
+
+ Symmetry, 39, 68, 70, 72, 89, 98
+
+ System, combined types of, 153 ff.
+ complex, 219 f.
+ complex-harmonious, 155
+ equipotential, 120
+ harmonious-equipotential, 121 ff., 151 f.
+ mixed-equipotential, 154
+ morphogenetic, 119 f., 163, 241
+
+ Systematics, 14 ff., 21, 243 f., 253, 264, 293, 296
+
+
+ Taine, 308, 310
+
+ Theology, natural, 1 ff.
+
+ Thomson, J. A., 16
+
+ Thymus, 204
+
+ Thyroid, 204
+
+ Tissue, 38
+
+ Toxins, 207 f.
+
+ Transformism, 251
+
+ Truth, 7
+
+ Tschermak, 228
+
+ *Tubularia*, 126 ff., 133, 158 ff.
+
+ Type, 48, 247 f., 282, 291
+
+
+ “Understanding” (historically), 302
+
+ Universality, postulate of, 148 f.
+
+ Universe, 5
+
+ Univocality, principle of, 161
+
+
+ “Values,” 317 ff.
+ prospective, 77 f., 80, 122
+
+ Variation, 218, 237 f., 276
+
+ Variation, fluctuating, contingent, 264 f., 273 f., 282, 290
+
+ Vernon, 232, 238
+
+ Vitalism, 143, 145 f., 210 f., 224 f., 234, 240 f., 272, 277
+
+ Vöchting, 174, 179 f., 182, 221
+
+ Volition, acts of, 274
+
+ Vries, de, 228, 238 f.
+
+
+ Wallace, 292
+
+ Ward, J., 8, 143
+
+ Weber, law of, 191
+
+ Weinland, 202
+
+ Weismann, 33, 52 ff., 58 f., 72, 74 f., 103,
+ 111, 138, 214 f., 237, 277 f.
+
+ Weldon, 238
+
+ Whole, the, 28, 80, 117
+ -embryo, 61, 67 f.
+
+ Wigand, 255, 266, 292
+
+ Wilson, E. B., 27, 65, 70 f., 86 f., 107
+
+ Windelband, 13 f.
+
+ Winkler, 116, 221
+
+ Winterstein, 199
+
+ Wolff, C. F., 26
+
+ Wolff, G., 105, 146, 255, 266, 287 f.
+
+ Wolff, J., 177
+
+
+ Yung, 177
+
+
+ Zeleny, 112, 115, 212
+
+ Zur Strassen, 93
+
+
+ THE END
+
+ *Printed by* R. & R. CLARK, LIMITED, *Edinburgh*.
+
+
+
+
+ HEREDITY AND SELECTION
+ IN SOCIOLOGY
+
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+ BY
+
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+
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+ RUDOLF EUCKEN’S
+ PHILOSOPHY OF LIFE
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+
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+
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+End of the Project Gutenberg EBook of The Science and Philosophy of the
+Organism, by Hans Driesch
+
+*** END OF THE PROJECT GUTENBERG EBOOK 44388 ***
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