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Hyperlinks to footnotes +and page references are indicated by black dotted underlines plus +aqua highlighting when the mouse pointer hovers over them. The +footnotes are themselves hyperlinked back to the originating marker +to facilitate easy return to the text. A red dashed underline as +shown <ins title="Comment">here</ins> indicates the presence of a +transcriber’s comment; scrolling the mouse pointer over such text +will reveal the comment.</p> + +<p>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.</p> + +<p>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.</p> + +<p>In Figure 12 caption, multiple ditto marks have been replaced by the +relevant text for greater clarity.</p> + +</div> + + +<p><span class="pagenum hide" title="i"><a name="Page_i" id="Page_i"></a></span></p> + +<p class="tac fs160 mt15em mb2em">THE SCIENCE AND PHILOSOPHY<br /> +OF THE ORGANISM</p> +<p><span class="pagenum hide" title="ii"><a name="Page_ii" id="Page_ii"></a></span></p> + +<table class="fs65 mb2em" border="0" cellpadding="4" cellspacing="0" summary="International addresses of publisher"> +<col width="30%" /><col width="70%" /> +<tr><td class="tac" colspan="2">AGENTS</td></tr> +<tr class="vat"><td><span class="smcap">America</span></td><td><span class="smcap">The Macmillan Company<br />64 & 66 Fifth Avenue, New York</span></td></tr> +<tr class="vat"><td><span class="smcap">Australasia</span></td><td><span class="smcap">The Oxford University Press, Melbourne</span></td></tr> +<tr class="vat"><td><span class="smcap">Canada</span></td><td><span class="smcap">The Macmillan Company of Canada, Ltd.<br />27 Richmond Street West, Toronto</span></td></tr> +<tr class="vat"><td><span class="smcap">India</span></td><td><span class="smcap">Macmillan & Company, Ltd.<br />Macmillan Building, Bombay<br />309 Bow Bazaar Street, Calcutta</span></td></tr> +</table> +<p><span class="pagenum hide" title="iii"><a name="Page_iii" id="Page_iii"></a></span></p> + + +<h1 class="lh150 mt15em"><span class="fs65">THE</span><br /> +SCIENCE AND PHILOSOPHY<br /> +OF THE ORGANISM</h1> + +<p class="tac ls01em mb2em lh150">THE GIFFORD LECTURES DELIVERED BEFORE<br /> +THE UNIVERSITY OF ABERDEEN<br /> +IN THE YEAR 1907<br /><br /></p> + +<p class="tac"><span class="fs85 lh300">BY</span><br /> +<span class="fs120">HANS DRIESCH, <span class="smcap">Ph.D.</span></span><br /> +<span class="fs50">HEIDELBERG</span><br /><br /><br /><br /> +<span class="figcenter" style="width: 321px;"> +<img id="logo" src="images/logo.png" width="53" height="52" alt="" /></span> +<br /><br /><br /></p> + + +<p class="tac ls01em mb2em lh150">LONDON<br /> +ADAM AND CHARLES BLACK<br /> +1908</p> + +<p class="tac fs65"><em>All rights reserved</em></p> +<hr class="short" /> +<p><span class="pagenum hide" title="iv"><a name="Page_iv" id="Page_iv"></a></span><br /><span class="pagenum" title="v"><a name="Page_v" id="Page_v"></a></span></p> + + + + +<h2>PREFACE</h2> + + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="vi"><a name="Page_vi" id="Page_vi"></a></span> +shortened, revised, and, as I hope, improved account of what +was published in my <cite lang="de" xml:lang="de">Analytische Theorie der organischen +Entwickelung</cite> (1894), <cite lang="de" xml:lang="de">Die Localisation morphogenetischer +Vorgänge; ein Beweis Vitalistischen Geschehens</cite> (1899), and +<cite lang="de" xml:lang="de">Die organischen Regulationen</cite> (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.</p> + +<p>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, <cite lang="de" xml:lang="de">Die “Seele” als elementarer Naturfactor</cite> (1903). +The greater part of this volume, however, will be devoted +to the “Philosophy of the Organism,” <i>i.e.</i> Section B, which, in +my opinion, includes the most important parts of the work.</p> + +<p>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<span class="pagenum" title="vii"><a name="Page_vii" id="Page_vii"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + + +<p>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.</p> + +<p class="tar mr2em">HANS DRIESCH.<br /><br /></p> + +<p><span class="smcap fs85">Heidelberg</span>, <i>2nd January 1908</i>.<br /></p> +<hr class="chap" /> + +<p><span class="pagenum hide" title="viii"><a name="Page_viii" id="Page_viii"></a></span><br /><span class="pagenum" title="ix"><a name="Page_ix" id="Page_ix"></a></span></p> + + + +<h2>CONTENTS OF THE FIRST VOLUME</h2> + +<p class="tac">THE PROGRAMME</p> + + +<div class="tac mb2em"> +<table width="85%" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tal"></td><td class="tar"><span class="fs85">PAGE</span></td></tr> +<tr><td class="tal">On Lord Gifford’s Conception of “Science”</td><td class="tar"><a href="#Page_1">1</a></td></tr> +<tr><td class="tal">Natural Sciences and “Natural Theology”</td><td class="tar"><a href="#Page_3">3</a></td></tr> +<tr><td class="tal">Our Philosophical Basis</td><td class="tar"><a href="#Page_5">5</a></td></tr> +<tr><td class="tal">On Certain Characteristics of Biology as a Science</td><td class="tar"><a href="#Page_9">9</a></td></tr> +<tr><td class="tal">The Three Different Types of Knowledge about Nature</td><td class="tar"><a href="#Page_13">13</a></td></tr> +<tr><td class="tal">General Plan of these Lectures</td><td class="tar"><a href="#Page_15">15</a></td></tr> +<tr><td class="tal">General Character of the Organic Form</td><td class="tar"><a href="#Page_19">19</a></td></tr> +</table></div> + + +<p class="tac">SECTION A.—THE CHIEF RESULTS OF ANALYTICAL BIOLOGY</p> + +<p class="tac">PART I.—THE INDIVIDUAL ORGANISM WITH REGARD TO<br />FORM AND METABOLISM</p> + +<div class="tac mb2em"> +<table width="85%" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tal pb05em"><i>A.</i> ELEMENTARY MORPHOGENESIS—</td><td></td></tr> +<tr><td class="tal pl2em">Evolutio and Epigenesis in the old Sense</td><td class="tar"><a href="#Page_25">25</a></td></tr> +<tr><td class="tal pl2em">The Cell</td><td class="tar"><a href="#Page_27">27</a></td></tr> +<tr><td class="tal pl2em">The Egg: its Maturation and Fertilisation</td><td class="tar"><a href="#Page_31">31</a></td></tr> +<tr><td class="tal pl2em">The First Developmental Processes of Echinus</td><td class="tar"><a href="#Page_33">33</a></td></tr> +<tr><td class="tal pl2em">Comparative Embryology</td><td class="tar"><a href="#Page_44">44</a></td></tr> +<tr><td class="tal pl2em">The First Steps of Analytical Morphogenesis</td><td class="tar"><a href="#Page_45">45</a></td></tr> +<tr><td class="tal pl2em pb15em">The Limits of Pure Description in Science</td><td class="tar pb15em"><a href="#Page_50">50</a></td></tr> +<tr><td class="tal pb05em"><i>B.</i> EXPERIMENTAL AND THEORETICAL MORPHOGENESIS—</td></tr> +<tr><td class="tal pl2em pr4em">1. <span class="smcap">The Foundations of the Physiology of Development. “Evolutio” and “Epigenesis”</span></td><td class="tar vab"><a href="#Page_52">52</a></td></tr> +<tr><td class="tal pl4em">The Theory of Weismann</td><td class="tar vab"><a href="#Page_52">52</a></td></tr> +<tr><td class="tal pl4em">Experimental Morphology</td><td class="tar vab"><a href="#Page_56">56</a></td></tr> +<tr><td class="tal pl4em"><span class="pagenum" title="x"><a name="Page_x" id="Page_x"></a></span>The Work of Wilhelm Roux</td><td class="tar vab"><a href="#Page_58">58</a></td></tr> +<tr><td class="tal pl4em">The Experiments on the Egg of the Sea-urchin</td><td class="tar vab"><a href="#Page_59">59</a></td></tr> +<tr><td class="tal pl4em">On the Intimate Structure of the Protoplasm of the Germ</td><td class="tar vab"><a href="#Page_65">65</a></td></tr> +<tr><td class="tal pl4em">On some Specificities of Organisation in Certain Germs</td><td class="tar vab"><a href="#Page_70">70</a></td></tr> +<tr><td class="tal pl4em">General Results of the First Period of “Entwickelungsmechanik”</td><td class="tar vab"><a href="#Page_71">71</a></td></tr> +<tr><td class="tal pl4em">Some New Results concerning Restitutions</td><td class="tar vab"><a href="#Page_74">74</a></td></tr> +<tr><td class="tal pl2em ptb05em">2. <span class="smcap">Analytical Theory of Morphogenesis</span></td><td class="tar"><a href="#Page_76">76</a></td></tr> +<tr><td class="tal pl4em">α. <span class="lowercase smcap">THE DISTRIBUTION OF MORPHOGENIC POTENCIES</span></td><td class="tar vab"><a href="#Page_76">76</a></td></tr> +<tr><td class="tal pl6em">Prospective Value and Prospective Potency</td><td class="tar vab"><a href="#Page_76">76</a></td></tr> +<tr><td class="tal pl6em">The Potencies of the Blastomeres</td><td class="tar vab"><a href="#Page_79">79</a></td></tr> +<tr><td class="tal pl6em">The Potencies of Elementary Organs in General</td><td class="tar vab"><a href="#Page_80">80</a></td></tr> +<tr><td class="tal pl6em">Explicit and Implicit Potencies: Primary and Secondary Potencies</td><td class="tar vab"><a href="#Page_83">83</a></td></tr> +<tr><td class="tal pl6em pr4em">The Morphogenetic Function of Maturation in the Light of Recent Discoveries</td><td class="tar vab"><a href="#Page_85">85</a></td></tr> +<tr><td class="tal pl6em">The Intimate Structure of Protoplasm: Further Remarks</td><td class="tar vab"><a href="#Page_88">88</a></td></tr> +<tr><td class="tal pl6em">The Neutrality of the Concept of “Potency”</td><td class="tar vab"><a href="#Page_89">89</a></td></tr> +<tr><td class="tal pl4em pt05em">β. <span class="lowercase smcap">THE “MEANS” OF MORPHOGENESIS</span></td><td class="tar vab"><a href="#Page_89">89</a></td></tr> +<tr><td class="tal pl6em">β′. The Internal Elementary Means of Morphogenesis</td><td class="tar vab"><a href="#Page_90">90</a></td></tr> +<tr><td class="tal pl8em pr4em">Some Remarks on the Importance of Surface Tension in Morphogenesis</td><td class="tar vab"><a href="#Page_91">91</a></td></tr> +<tr><td class="tal pl8em">On Growth</td><td class="tar vab"><a href="#Page_93">93</a></td></tr> +<tr><td class="tal pl8em">On Cell-division</td><td class="tar vab"><a href="#Page_94">94</a></td></tr> +<tr><td class="tal pl6em">β″. The External Means of Morphogenesis</td><td class="tar vab"><a href="#Page_95">95</a></td></tr> +<tr><td class="tal pl8em">The Discoveries of Herbst</td><td class="tar vab"><a href="#Page_96">96</a></td></tr> +<tr><td class="tal pl4em pt05em">γ. <span class="lowercase smcap">THE FORMATIVE CAUSES OR STIMULI</span></td><td class="tar vab"><a href="#Page_99">99</a></td></tr> +<tr><td class="tal pl6em">The Definition of Cause</td><td class="tar vab"><a href="#Page_99">99</a></td></tr> +<tr><td class="tal pl6em">Some Instances of Formative and Directive Stimuli</td><td class="tar vab"><a href="#Page_102">102</a></td></tr> +<tr><td class="tal pl4em pt05em">δ. <span class="lowercase smcap">THE MORPHOGENETIC HARMONIES</span></td><td class="tar vab"><a href="#Page_107">107</a></td></tr> +<tr><td class="tal pl4em pt05em">ε. <span class="lowercase smcap">ON RESTITUTIONS</span></td><td class="tar vab"><a href="#Page_110">110</a></td></tr> +<tr><td class="tal pl6em pr4em">A few Remarks on Secondary Potencies and on Secondary Morphogenetic Regulations in General</td><td class="tar vab"><a href="#Page_110">110</a></td></tr> +<tr><td class="tal pl6em">The Stimuli of Restitutions</td><td class="tar vab"><a href="#Page_113">113</a></td></tr> +<tr><td class="tal pl2em ptb05em pr4em">3. <span class="smcap">The Problem of Morphogenetic Localisation: The Theory of the Harmonious-Equipotential system—First Proof of the Autonomy of Life</span></td><td class="tar vab ptb05em"><a href="#Page_118">118</a></td></tr> +<tr><td class="tal pl4em">The General Problem</td><td class="tar vab"><a href="#Page_118">118</a></td></tr> +<tr><td class="tal pl4em">The Morphogenetic “System”</td><td class="tar vab"><a href="#Page_119">119</a></td></tr> +<tr><td class="tal pl4em">The “Harmonious-equipotential System”</td><td class="tar vab"><a href="#Page_122">122</a></td></tr> +<tr><td class="tal pl4em"><span class="pagenum" title="xi"><a name="Page_xi" id="Page_xi"></a></span>Instances of “Harmonious-equipotential Systems”</td><td class="tar vab"><a href="#Page_126">126</a></td></tr> +<tr><td class="tal pl4em">The Problem of the Factor <i>E</i></td><td class="tar vab"><a href="#Page_132">132</a></td></tr> +<tr><td class="tal pl4em">No Explanation offered by “Means” or “Formative Stimuli”</td><td class="tar vab"><a href="#Page_132">132</a></td></tr> +<tr><td class="tal pl4em">No Explanation offered by a Chemical Theory of Morphogenesis</td><td class="tar vab"><a href="#Page_134">134</a></td></tr> +<tr><td class="tal pl4em">No Machine Possible Inside the Harmonious Systems</td><td class="tar vab"><a href="#Page_138">138</a></td></tr> +<tr><td class="tal pl4em">The Autonomy of Morphogenesis proved</td><td class="tar vab"><a href="#Page_142">142</a></td></tr> +<tr><td class="tal pl4em">“Entelechy”</td><td class="tar vab"><a href="#Page_143">143</a></td></tr> +<tr><td class="tal pl4em">Some General Remarks on Vitalism</td><td class="tar vab"><a href="#Page_145">145</a></td></tr> +<tr><td class="tal pl4em">The Logic of our First Proof of Vitalism</td><td class="tar vab"><a href="#Page_146">146</a></td></tr> +<tr><td class="tal pl2em ptb05em pr4em">4. <span class="smcap">On Certain other Features of Morphogenesis Advocating its Autonomy</span></td><td class="tar vab ptb05em"><a href="#Page_150">150</a></td></tr> +<tr><td class="tal pl4em">Harmonious-equipotential Systems formed by Wandering Cells</td><td class="tar vab"><a href="#Page_151">151</a></td></tr> +<tr><td class="tal pl4em">On Certain Combined Types of Morphogenetic Systems</td><td class="tar vab"><a href="#Page_153">153</a></td></tr> +<tr><td class="tal pl4em">The “Morphaesthesia” of Noll</td><td class="tar vab"><a href="#Page_157">157</a></td></tr> +<tr><td class="tal pl4em">Restitutions of the Second Order</td><td class="tar vab"><a href="#Page_158">158</a></td></tr> +<tr><td class="tal pl4em">On the “Equifinality” of Restitutions</td><td class="tar vab"><a href="#Page_159">159</a></td></tr> +<tr><td class="tal pl4em pb15em">Remarks on “Retro-Differentiation”</td><td class="tar pb15em"><a href="#Page_163">163</a></td></tr> +<tr><td class="tal pb05em"><i>C.</i> ADAPTATION—</td></tr> +<tr><td class="tal pl2em"><span class="smcap">Introductory Remarks on Regulations in General</span></td><td class="tar vab"><a href="#Page_165">165</a></td></tr> +<tr><td class="tal pl2em ptb05em">1. <span class="smcap">Morphological Adaptation</span></td><td class="tar"><a href="#Page_168">168</a></td></tr> +<tr><td class="tal pl4em">The Limits of the Concept of Adaptation</td><td class="tar vab"><a href="#Page_168">168</a></td></tr> +<tr><td class="tal pl4em">Adaptations to Functional Changes from Without</td><td class="tar vab"><a href="#Page_172">172</a></td></tr> +<tr><td class="tal pl4em">True Functional Adaptation</td><td class="tar vab"><a href="#Page_176">176</a></td></tr> +<tr><td class="tal pl4em">Theoretical Conclusions</td><td class="tar vab"><a href="#Page_179">179</a></td></tr> +<tr><td class="tal pl2em ptb05em">2. <span class="smcap">Physiological Adaptation</span></td><td class="tar"><a href="#Page_184">184</a></td></tr> +<tr><td class="tal pl4em">Specific Adaptedness <em>not</em> “Adaptation”</td><td class="tar vab"><a href="#Page_186">186</a></td></tr> +<tr><td class="tal pl4em">Primary and Secondary Adaptations in Physiology</td><td class="tar vab"><a href="#Page_188">188</a></td></tr> +<tr><td class="tal pl4em">On Certain Pre-requisites of Adaptations in General</td><td class="tar vab"><a href="#Page_189">189</a></td></tr> +<tr><td class="tal pl4em">On Certain Groups of Primary Physiological Adaptations</td><td class="tar vab"><a href="#Page_190">190</a></td></tr> +<tr><td class="tal pl6em">General Remarks on Irritability</td><td class="tar vab"><a href="#Page_190">190</a></td></tr> +<tr><td class="tal pl6em">The Regulation of Heat Production</td><td class="tar vab"><a href="#Page_193">193</a></td></tr> +<tr><td class="tal pl6em pr4em">Primary Regulations in the Transport of Materials and Certain Phenomena of Osmotic Pressure</td><td class="tar vab"><a href="#Page_194">194</a></td></tr> +<tr><td class="tal pl6em">Chromatic Regulations in Algae</td><td class="tar vab"><a href="#Page_197">197</a></td></tr> +<tr><td class="tal pl6em">Metabolic Regulations</td><td class="tar vab"><a href="#Page_198">198</a></td></tr> +<tr><td class="tal pl4em">Immunity the only Type of a Secondary Physiological Adaptation</td><td class="tar vab"><a href="#Page_204">204</a></td></tr> +<tr><td class="tal pl4em">No General Positive Result from this Chapter</td><td class="tar vab"><a href="#Page_209">209</a></td></tr> +<tr><td class="tal pl4em pb15em">A few Remarks on the Limits of Regulability</td><td class="tar pb15em"><a href="#Page_212">212</a></td></tr> +<tr><td class="tal pb05em"><span class="pagenum" title="xii"><a name="Page_xii" id="Page_xii"></a></span><i>D.</i> INHERITANCE. SECOND PROOF OF THE AUTONOMY OF LIFE—</td></tr> +<tr><td class="tal pl2em">The Material Continuity in Inheritance</td><td class="tar vab"><a href="#Page_214">214</a></td></tr> +<tr><td class="tal pl2em">On Certain Theories which Seek to Compare Inheritance to Memory</td><td class="tar vab"><a href="#Page_216">216</a></td></tr> +<tr><td class="tal pl2em">The Complex-Equipotential System and its Rôle in Inheritance</td><td class="tar vab"><a href="#Page_219">219</a></td></tr> +<tr><td class="tal pl2em pr4em">The Second Proof of Life-Autonomy. Entelechy at the Bottom of Inheritance</td><td class="tar vab"><a href="#Page_224">224</a></td></tr> +<tr><td class="tal pl2em">The Significance of the Material Continuity in Inheritance</td><td class="tar vab"><a href="#Page_227">227</a></td></tr> +<tr><td class="tal pl2em">The Experimental Facts about Inheritance</td><td class="tar vab"><a href="#Page_228">228</a></td></tr> +<tr><td class="tal pl2em">The Rôle of the Nucleus in Inheritance</td><td class="tar vab"><a href="#Page_233">233</a></td></tr> +<tr><td class="tal pl2em pb15em">Variation and Mutation</td><td class="tar pb15em"><a href="#Page_237">237</a></td></tr> +<tr><td class="tal"><i><span class="smcap">Conclusions from the First Main Part of these Lectures</span></i></td><td class="tar vab"><a href="#Page_240">240</a></td></tr> +</table></div> + +<p class="tac">PART II.—SYSTEMATICS AND HISTORY</p> + +<div class="tac mb2em"> +<table width="85%" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tal pb05em"><i>A.</i> THE PRINCIPLES OF SYSTEMATICS—</td></tr> +<tr><td class="tal pl2em">Rational Systematics</td><td class="tar vab"><a href="#Page_243">243</a></td></tr> +<tr><td class="tal pl2em pb15em">Biological Systematics</td><td class="tar pb15em"><a href="#Page_246">246</a></td></tr> +<tr><td class="tal pb05em"><i>B.</i> THE THEORY OF DESCENT—</td></tr> +<tr><td class="tal pl2em ptb05em">1. <span class="smcap">Generalities</span></td><td class="tar"><a href="#Page_250">250</a></td></tr> +<tr><td class="tal pl4em">The Covert Presumption of all Theories of Descent</td><td class="tar vab"><a href="#Page_253">253</a></td></tr> +<tr><td class="tal pl4em">The Small Value of Pure Phylogeny</td><td class="tar vab"><a href="#Page_255">255</a></td></tr> +<tr><td class="tal pl4em">History and Systematics</td><td class="tar vab"><a href="#Page_257">257</a></td></tr> +<tr><td class="tal pl2em ptb05em">2. <span class="smcap">The Principles of Darwinism</span></td><td class="tar"><a href="#Page_260">260</a></td></tr> +<tr><td class="tal pl4em">Natural Selection</td><td class="tar vab"><a href="#Page_261">261</a></td></tr> +<tr><td class="tal pl4em">Fluctuating Variation the Alleged Cause of Organic Diversity</td><td class="tar vab"><a href="#Page_264">264</a></td></tr> +<tr><td class="tal pl4em">Darwinism Fails all along the Line</td><td class="tar vab"><a href="#Page_269">269</a></td></tr> +<tr><td class="tal pl2em ptb05em">3. <span class="smcap">The Principles of Lamarckism</span></td><td class="tar"><a href="#Page_271">271</a></td></tr> +<tr><td class="tal pl4em">Adaptation as the Starting-Point</td><td class="tar vab"><a href="#Page_272">272</a></td></tr> +<tr><td class="tal pl4em">The Active Storing of Contingent Variations as a Hypothetic Principle</td><td class="tar vab"><a href="#Page_273">273</a></td></tr> +<tr><td class="tal pl4em pr4em">Criticism of the “Inheritance of Acquired Characters” assumed by Lamarckism</td><td class="tar vab"><a href="#Page_275">275</a></td></tr> +<tr><td class="tal pl4em">Other Principles Wanted</td><td class="tar vab"><a href="#Page_281">281</a></td></tr> +<tr><td class="tal pl4em pr4em">Criticism of the Hypothesis of Storing and Handing Down Contingent Variations</td><td class="tar vab"><a href="#Page_282">282</a></td></tr> +<tr><td class="tal pl2em ptb05em">4. <span class="smcap">The Real Results and the Unsolved Problems of Transformism</span></td><td class="tar ptb05em"><a href="#Page_290">290</a></td></tr> +<tr><td class="tal pl2em ptb05em pr4em">5. <span class="smcap">The Logical Value of the Organic Form according to the different Transformistic Theories</span></td><td class="tar ptb05em vab"><a href="#Page_293">293</a></td></tr> +<tr><td class="tal pl4em pb15em">The Organic Form and Entelechy</td><td class="tar pb15em"><a href="#Page_294">294</a></td></tr> +<tr><td class="tal pb05em"><i>C.</i> THE LOGIC OF HISTORY</td><td class="tar pb05em"><a href="#Page_297">297</a><span class="pagenum" title="xiii"><a name="Page_xiii" id="Page_xiii"></a></span></td></tr> +<tr><td class="tal pl2em pb05em">1. <span class="smcap">The Possible Aspects of History</span></td><td class="tar pb05em"><a href="#Page_299">299</a></td></tr> +<tr><td class="tal pl2em pb05em">2. <span class="smcap">Phylogenetic Possibilities</span></td><td class="tar pb05em"><a href="#Page_304">304</a></td></tr> +<tr><td class="tal pl2em pb05em">3. <span class="smcap">The History of Mankind</span></td><td class="tar pb05em"><a href="#Page_306">306</a></td></tr> +<tr><td class="tal pl4em">Cumulations in Human History</td><td class="tar vab"><a href="#Page_308">308</a></td></tr> +<tr><td class="tal pl4em">Human History not an “Evolution”</td><td class="tar vab"><a href="#Page_311">311</a></td></tr> +<tr><td class="tal pl4em pb15em">The Problem of the “Single” as such</td><td class="tar pb15em"><a href="#Page_315">315</a></td></tr> +<tr><td class="tal pb05em"><i><span class="smcap">Conclusions about Systematics and History in General</span></i></td><td class="tar pb05em"><a href="#Page_322">322</a></td></tr> +</table></div> + +<p><span class="pagenum hide" title="xiv"><a name="Page_xiv" id="Page_xiv"></a></span></p> + +<hr class="chap" /> + +<p><span class="pagenum" title="1"><a name="Page_1" id="Page_1"></a></span></p> + + + +<h2>THE PROGRAMME</h2> + + +<p class="tac ptb05em"><span class="smcap">On Lord Gifford’s Conception of “Science”</span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="2"><a name="Page_2" id="Page_2"></a></span> +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.”</p> + +<p>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 <em>the</em> +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<span class="pagenum" title="3"><a name="Page_3" id="Page_3"></a></span> +to be delivered “without reference to or reliance upon +any supposed special exceptional or so-called miraculous +revelation.”</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="smcap">Natural Sciences and “Natural Theology”</span></p> + +<p>But now let us study in a more systematic manner the +possible relations of the natural sciences to natural theology +as a science.</p> + +<p>How is it possible for a natural scientist to contribute +to the science of the highest and ultimate subject of human +knowledge?</p> + +<p>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.</p> + +<p>It is only by the aid of philosophy, or I would rather +say by keeping in constant touch with it, that natural<span class="pagenum" title="4"><a name="Page_4" id="Page_4"></a></span> +sciences are able to acquire any significance for what might +be called <em>the</em> 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>i.e.</i> what in German, for instance, would +simply be called “Naturphilosophie.”</p> + +<p>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.</p> + +<p>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?</p> + +<p>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,<span class="pagenum" title="5"><a name="Page_5" id="Page_5"></a></span> +applicable to the totality of questions asked by all the +branches of philosophy.</p> + +<p>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.</p> + +<p>That is to be our subject.</p> + + +<p class="tac pt12b02em"><span class="smcap">Our Philosophical Basis</span></p> + +<p>We call <em>nature</em> what is given to us in space.</p> + +<p>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.</p> + +<p>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 <em>only my</em> 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 <em>is</em> as truly as I<span class="pagenum" title="6"><a name="Page_6" id="Page_6"></a></span> +am—though in a somewhat different sense of “being”—and +I <em>am</em> 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.</p> + +<p>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 <i lang="la" xml:lang="la">a priori</i>, 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 +<i lang="la" xml:lang="la">a priori</i>” 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 “<i lang="la" xml:lang="la">a priori</i>” as “independent of the <em>amount</em> +of experience”; that is to say, all categories and categorical +principles are brought to my consciousness by that<span class="pagenum" title="7"><a name="Page_7" id="Page_7"></a></span> +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.</p> + +<p>But enough at present about our general philosophy.</p> + +<p>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.”</p> + +<p>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<span class="pagenum" title="8"><a name="Page_8" id="Page_8"></a></span> +system themselves, and that there are no features in them +which impel our categorical Ego to further analysis.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="9"><a name="Page_9" id="Page_9"></a></span> +combination of more simple factors of the physical and +chemical type.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="smcap">On Certain Characteristics of Biology as a Science</span></p> + +<p>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<span class="pagenum" title="10"><a name="Page_10" id="Page_10"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="11"><a name="Page_11" id="Page_11"></a></span> +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.</p> + +<p>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,<span class="pagenum" title="12"><a name="Page_12" id="Page_12"></a></span> +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.</p> + +<p>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 <em>are</em>, 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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="13"><a name="Page_13" id="Page_13"></a></span></p> + + +<p class="tac pt12b02em"><span class="smcap">The three Different Types of Knowledge about Nature</span></p> + +<p>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.</p> + +<p>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.</p> + +<p>Using for our purposes a word which has been already +introduced into terminology by the philosopher Windelband,<span class="pagenum" title="14"><a name="Page_14" id="Page_14"></a></span> +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>i.e.</i> “law-giving.”</p> + +<p>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.</p> + +<p>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.</p> + +<p>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 <span class="nowrap">half.<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">1</a></span></p> +<p><span class="pagenum" title="15"><a name="Page_15" id="Page_15"></a></span></p> + +<p class="tac pt12b02em"><span class="smcap">General Plan of these Lectures</span></p> + +<p>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.</p> + +<p>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.</p> + +<p>Whilst regarding the whole of the biological material<span class="pagenum" title="16"><a name="Page_16" id="Page_16"></a></span> +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 <span class="nowrap">select,<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">2</a></span> 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.</p> + +<p>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.</p> + +<p>But at present it is enough to understand the terms +“body” and “living” in the ordinary and popular sense.</p> + +<p>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.</p> + +<p>Therefore we may ask for “laws of nature” in biology<span class="pagenum" title="17"><a name="Page_17" id="Page_17"></a></span> +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.</p> + +<p>It is <em>form</em> 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<span class="pagenum" title="18"><a name="Page_18" id="Page_18"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>Goethe once said, that even in so-called facts there is +more “theory” than is usually granted; he apparently was<span class="pagenum" title="19"><a name="Page_19" id="Page_19"></a></span> +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.</p> + +<p>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 +<em>most</em> 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.</p> + + +<p class="tac pt12b02em"><span class="smcap">General Character of the Organic Form</span></p> + +<p>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?</p> + +<p>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<span class="pagenum" title="20"><a name="Page_20" id="Page_20"></a></span> +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 <em>morphogenesis</em> +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 <em>physiology of morphogenesis</em>.</p> + +<p>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.</p> + +<p>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.<span class="pagenum" title="21"><a name="Page_21" id="Page_21"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="22"><a name="Page_22" id="Page_22"></a></span> +and physical events, or whether it has its elemental laws, +laws of its own.</p> + +<p>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.</p> + +<hr class="chap" /> + +<p><span class="pagenum hide" title="23"><a name="Page_23" id="Page_23"></a></span></p> + + + + +<h2>SECTION A</h2> + +<h3>THE CHIEF RESULTS OF ANALYTICAL +BIOLOGY</h3> + +<hr class="chap" /> + +<p><span class="pagenum hide" title="24"><a name="Page_24" id="Page_24"></a></span><br /><span class="pagenum" title="25"><a name="Page_25" id="Page_25"></a></span></p> + + + +<h2>PART I</h2> + +<h2>THE INDIVIDUAL ORGANISM WITH REGARD TO<br /> +FORM AND METABOLISM</h2> + +<h3><i>A.</i> ELEMENTARY MORPHOGENESIS</h3> + +<p class="tac ptb05em"><span class="smcap">Evolutio and Epigenesis in the old Sense</span></p> + +<p>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.</p> + +<p>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<span class="pagenum" title="26"><a name="Page_26" id="Page_26"></a></span> +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.</p> + +<p>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.</p> + +<p>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 <em>impossible</em>, +said the one party, that there is any real production of new +parts; there <em>must</em> be such a production, said the other.</p> + +<p>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 <em>is</em> a “production of visible manifoldness” during<span class="pagenum" title="27"><a name="Page_27" id="Page_27"></a></span> +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.</p> + +<p>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 +(<i class="biological-name">Echinus microtuberculatus</i>) 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 <i lang="la" xml:lang="la">conditio sine qua non</i> +for a real understanding of what is to follow.</p> + + +<p class="tac pt12b02em"><span class="smcap">The Cell</span><a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">3</a></p> + +<p>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.</p> + +<p>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,<span class="pagenum" title="28"><a name="Page_28" id="Page_28"></a></span> +on the other hand, all attempts to conceive the organism as +a mere aggregate of cells have proved to be wrong. It is +<em>the whole</em> 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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="29"><a name="Page_29" id="Page_29"></a></span> +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.<span class="pagenum" title="30"><a name="Page_30" id="Page_30"></a></span> +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.</p> + +<p>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).</p> + +<div class="figcenter" style="width: 420px;"> +<img src="images/fig01.jpg" width="420" height="460" alt="" /> +<p><span class="smcap">Fig. 1.—Diagram of Cell-Division</span> (<em>after</em> Boveri).</p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a.</i></td><td class="tal ti">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.</td></tr> +<tr><td class="tar vat"><i>b.</i></td><td class="tal ti">Beginning of division; the chromatin arranged in the form of a long thread. Centrosome divided in two.</td></tr> +<tr><td class="tar vat"><i>c.</i></td><td class="tal ti">The thread of chromatin cut into four parts, the “chromosomes.”</td></tr> +<tr><td class="tar vat"><i>d.</i></td><td class="tal ti">The four parts of the chromatin arranged symmetrically between the centrosomes and the star-like “spheres.”</td></tr> +<tr><td class="tar vat"><i>e.</i></td><td class="tal ti">Each of the chromosomes split at full length.</td></tr> +<tr><td class="tar vat"><i>f.</i></td><td class="tal ti">Beginning of division of protoplasm; the two parts of each chromosome separated.</td></tr> +<tr><td class="tar vat"><i>g.</i></td><td class="tal ti">End of cell-division.</td></tr> +</table> +</div> + +<p>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.</p> + +<p><span class="pagenum" title="31"><a name="Page_31" id="Page_31"></a></span></p> + + +<p class="tac pt12b02em"><span class="smcap">The Egg: its Maturation and Fertilisation</span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>The ripe or mature egg is capable of being fertilised.</p> + +<p>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 <span class="pagenum" title="32"><a name="Page_32" id="Page_32"></a></span>“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 <span class="nowrap">Loeb<a name="FNanchor_4_4" id="FNanchor_4_4"></a><a href="#Footnote_4_4" class="fnanchor">4</a></span> 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 <span class="nowrap">resort.<a name="FNanchor_5_5" id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">5</a></span></p> + +<p>But enough about processes, which at present are of a +highly scientific, but hardly of any philosophic interest.</p> + +<p>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<span class="pagenum" title="33"><a name="Page_33" id="Page_33"></a></span> +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.</p> + +<p>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.</p> + +<p>But we cannot enter here more fully into the physiology +of fertilisation, and shall only remark that its real significance +is by no means <span class="nowrap">clear.<a name="FNanchor_6_6" id="FNanchor_6_6"></a><a href="#Footnote_6_6" class="fnanchor">6</a></span></p> + + +<p class="tac pt12b02em"><span class="smcap">The First Development Process of Echinus</span></p> + +<p>Turning now definitively to the special kind of organism, +chosen of our type, the common sea-urchin, we properly<span class="pagenum" title="34"><a name="Page_34" id="Page_34"></a></span> +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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="35"><a name="Page_35" id="Page_35"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="36"><a name="Page_36" id="Page_36"></a></span> +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<span class="pagenum" title="37"><a name="Page_37" id="Page_37"></a></span> +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<sup>10</sup>.</p> + +<p>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).</p> + +<div class="figcenter" style="width: 428px;"> +<img src="images/fig02.jpg" width="428" height="337" alt="" /> +<p><span class="smcap">Fig. 2.—Early Development of Echinus, the Common Sea-urchin.</span></p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a.</i></td><td class="tal ti">Two cells.</td></tr> +<tr><td class="tar vat"><i>b.</i></td><td class="tal ti">Four cells.</td></tr> +<tr><td class="tar vat"><i>c.</i></td><td class="tal ti">Eight cells, arranged in two rings of four, above one another.</td></tr> +<tr><td class="tar vat"><i>d.</i></td><td class="tal ti">Sixteen cells, four “micromeres” formed at the “vegetative” pole.</td></tr> +<tr><td class="tar vat"><i>e.</i></td><td class="tal ti">Optical section of the “blastula,” a hollow sphere consisting of about one thousand cells, each of them with a small cilium.</td></tr> +</table> +</div> + +<p>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 <em>part</em> of the germ becoming<span class="pagenum" title="38"><a name="Page_38" id="Page_38"></a></span> +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.”</p> + +<p>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.</p> + +<p>At one pole of the swimming blastula, exactly at the +point where the descendants of the micromeres are situated,<span class="pagenum" title="39"><a name="Page_39" id="Page_39"></a></span> +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.</p> + +<p>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>i.e.</i> “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>i.e.</i> 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<span class="pagenum" title="40"><a name="Page_40" id="Page_40"></a></span> +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 <em>originates</em>. +The germ had an upper and a lower side before: it now +has got an upper and lower, front and back, <em>right and left</em> +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.</p> + +<div class="figcenter" style="width: 424px;"> +<img src="images/fig03.jpg" width="424" height="250" alt="" /> +<p><span class="smcap">Fig. 3.—Formation of Mesenchyme in Echinus.</span></p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a.</i> </td><td class="tal ti">Outlines of blastula, side-view; mesenchyme forms a heap of cells at the “vegetative” pole.</td></tr> +<tr><td class="tar vat"><i>a</i><sub>1</sub>.</td><td class="tal ti">Heap of mesenchyme-cells from above.</td></tr> +<tr><td class="tar vat"><i>b.</i> </td><td class="tal ti">Mesenchyme-cells arranged in a ring round the vegetative pole.</td></tr> +<tr><td class="tar vat"><i>c.</i> </td><td class="tal ti">Mesenchyme-cells arranged in a bilateral-symmetrical figure; primordia of skeleton in the midst of two spherical triangles.</td></tr> +</table> +</div> + +<p>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<span class="pagenum" title="41"><a name="Page_41" id="Page_41"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="42"><a name="Page_42" id="Page_42"></a></span> +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.</p> + +<p>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<span class="pagenum" title="43"><a name="Page_43" id="Page_43"></a></span> +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.</p> + +<div class="figcenter" style="width: 392px;"> +<img src="images/fig04.jpg" width="392" height="317" alt="" /> +<p><span class="smcap">Fig. 4.—Larval Development of Echinus.</span></p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>A.</i></td><td class="tal ti">The gastrula.</td></tr> +<tr><td class="tar vat"><i>B.</i></td><td class="tal ti">Later stage, bilateral-symmetrical. Intestine begins to divide into three parts.</td></tr> +<tr><td class="tar vat"><i>C.</i></td><td class="tal ti">Pluteus larva. S = Skeleton. I = Intestine.</td></tr> +</table> +</div> + +<p>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.</p> + +<p>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<span class="pagenum" title="44"><a name="Page_44" id="Page_44"></a></span> +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.</p> + + +<p class="tac pt12b02em"><span class="smcap">Comparative Embryology</span></p> + +<p>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<span class="pagenum" title="45"><a name="Page_45" id="Page_45"></a></span> +would seem to us probably so great that all the similarities +would seem to disappear.</p> + +<p>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?</p> + + +<p class="tac pt12b02em"><span class="smcap">The First Steps of Analytical Morphogenesis</span></p> + +<p>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 <em>is</em> 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.</p> + +<p>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,<span class="pagenum" title="46"><a name="Page_46" id="Page_46"></a></span> +though in a smaller form; there is no “evolutio” in the old +meaning of the word.</p> + +<p>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 +<i lang="la" xml:lang="la">evolutio</i>. 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.</p> + +<p>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<span class="pagenum" title="47"><a name="Page_47" id="Page_47"></a></span> +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.</p> + +<p>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 <em>position</em> of embryonic parts is more strict than +in their histology.</p> + +<p>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<span class="pagenum" title="48"><a name="Page_48" id="Page_48"></a></span> +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 <span class="nowrap">them.<a name="FNanchor_7_7" id="FNanchor_7_7"></a><a href="#Footnote_7_7" class="fnanchor">7</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p>Our mention of plants leads us to the last of our +analytical results. If an animal germ proceeds in its +development from a stage <i>d</i> to the stage <i>g</i>, passing through +<i>e</i> and <i>f</i>, we may say that the whole of <i>d</i> has become the +whole of <i>f</i>, but we cannot say that there is a certain part of +<i>f</i> which is <i>d</i>, we cannot say that <i>f</i> is <i>d</i> + <i>a</i>. But in plants +we can: the stage <i>f</i> is indeed equal to <i>a</i> + <i>b</i> + <i>c</i> + <i>d</i> + <i>e</i> + <ins title="Transcriber's Note: ? typo for f "><i>a</i></ins> in vegetable organisms; all earlier stages are actually visible +as parts of the last one. The great embryologist, Carl Ernst<span class="pagenum" title="49"><a name="Page_49" id="Page_49"></a></span> +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 <em>lost</em> 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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="50"><a name="Page_50" id="Page_50"></a></span></p> + + +<p class="tac pt12b02em"><span class="smcap">The Limits of Pure Description in Science</span></p> + +<p>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.</p> + +<p>There is a very famous dictum in the <cite>Treatise on +Mechanics</cite> 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 <em>given</em> +bodies and processes are to be compared!</p> + +<p>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<span class="pagenum" title="51"><a name="Page_51" id="Page_51"></a></span> +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 <span class="nowrap">itself.<a name="FNanchor_8_8" id="FNanchor_8_8"></a><a href="#Footnote_8_8" class="fnanchor">8</a></span></p> + +<p>It is the <em>method</em> 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.</p> + +<p>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.</p> + +<hr /> + +<p><span class="pagenum" title="52"><a name="Page_52" id="Page_52"></a></span></p> + + + + +<h3><i>B.</i> EXPERIMENTAL AND THEORETICAL MORPHOGENESIS</h3> + +<h4 class="fs120">1. <span class="smcap">The Foundations of the Physiology of Development.<br /> +“Evolutio” and “Epigenesis”</span></h4> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE THEORY OF WEISMANN</span></p> + +<p>Of all the purely hypothetic theories on morphogenesis +that of August <span class="nowrap">Weismann<a name="FNanchor_9_9" id="FNanchor_9_9"></a><a href="#Footnote_9_9" class="fnanchor">9</a></span> 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.</p> + +<p>Weismann assumes that a very complicated organised +structure, below the limits of visibility even with the<span class="pagenum" title="53"><a name="Page_53" id="Page_53"></a></span> +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.</p> + +<p>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 <em>fundamental</em> 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.</p> + +<p><span class="pagenum" title="54"><a name="Page_54" id="Page_54"></a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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 <em>visible</em> sense is produced, but +that epigenesis can never form the foundation of a real +morphogenetic <em>theory</em>: theoretically one pre-existing manifoldness +is transformed into the other. An epigenetic +theory would lead right beyond natural science, Weismann<span class="pagenum" title="55"><a name="Page_55" id="Page_55"></a></span> +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.</p> + +<p>Under these circumstances we have a good right, it +seems to me, to speak of a <em>dogmatic</em> basis of Weismann’s +theory of development.</p> + +<p>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.</p> + +<p>Almost independently another German author, Wilhelm +<span class="nowrap">Roux,<a name="FNanchor_10_10" id="FNanchor_10_10"></a><a href="#Footnote_10_10" class="fnanchor">10</a></span> 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.</p> + +<p>But in spite of this similarity of the outset, we enter an<span class="pagenum" title="56"><a name="Page_56" id="Page_56"></a></span> +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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">EXPERIMENTAL MORPHOLOGY</span></p> + +<p>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.</p> + +<p>There were always a few men, of course, who strove +against the current. The late Wilhelm <span class="nowrap">His,<a name="FNanchor_11_11" id="FNanchor_11_11"></a><a href="#Footnote_11_11" class="fnanchor">11</a></span> for 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 <span class="nowrap">Goette<a name="FNanchor_12_12" id="FNanchor_12_12"></a><a href="#Footnote_12_12" class="fnanchor">12</a></span><span class="pagenum" title="57"><a name="Page_57" id="Page_57"></a></span> +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 <span class="nowrap">Roux,<a name="FNanchor_13_13" id="FNanchor_13_13"></a><a href="#Footnote_13_13" class="fnanchor">13</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="58"><a name="Page_58" id="Page_58"></a></span> +relations Wilhelm Roux established with the aid of +morphogenetic experiment.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE WORK OF WILHELM ROUX</span></p> + +<p>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.</p> + +<p>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, <i>e.g.</i> 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.</p> + +<p>But Roux was not satisfied with mere indicia, he<span class="pagenum" title="59"><a name="Page_59" id="Page_59"></a></span> +wanted a proof, and with this intention he carried out +an experiment which has become very <span class="nowrap">celebrated.<a name="FNanchor_14_14" id="FNanchor_14_14"></a><a href="#Footnote_14_14" class="fnanchor">14</a></span> 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.</p> + +<p>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.”</p> + +<p>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.</p> + +<p>Things soon became still more ambiguous.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE EXPERIMENTS ON THE EGG OF THE SEA-URCHIN</span></p> + +<p>Roux’s results were published for the first time in +1888; three years later I tried to repeat his fundamental<span class="pagenum" title="60"><a name="Page_60" id="Page_60"></a></span> +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 (<i class="biological-name">Echinus microtuberculatus</i>) 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 <span class="nowrap">another.<a name="FNanchor_15_15" id="FNanchor_15_15"></a><a href="#Footnote_15_15" class="fnanchor">15</a></span></p> + +<p>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.</p> + +<p>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 <em>whole</em> diminutive<span class="pagenum" title="61"><a name="Page_61" id="Page_61"></a></span> +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.</p> + +<p>But things turned out as they were bound to do and +not as I had expected; there was a typically <em>whole</em> gastrula +on my dish the next morning, differing only by its small +size from a normal one; and this <em>small but whole</em> gastrula +was followed by a whole and typical small pluteus-larva +(Fig. 5).</p> + +<div class="figcenter" style="width: 460px;"> +<img src="images/fig05.jpg" width="460" height="320" alt="" /> +<p><span class="smcap">Fig. 5.—Illustration of Experiments on Echinus.</span></p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a</i><sub>1</sub> and <i>b</i><sub>1</sub>.</td><td class="tal ti">Normal gastrula and normal pluteus.</td></tr> +<tr><td class="tar vat"><i>a</i><sub>2</sub> and <i>b</i><sub>2</sub>.</td><td class="tal ti">“Half”-gastrula and “half”-pluteus, that <em>ought</em> to result from one of the first two blastomeres, when isolated, according to the theory of “evolutio.”</td></tr> +<tr><td class="tar vat"><i>a</i><sub>3</sub> and <i>b</i><sub>3</sub>.</td><td class="tal ti">The small <em>but whole</em> gastrula and pluteus that actually <em>do</em> result.</td></tr> +</table> +</div> + +<p>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.</p> + +<p>If one blastomere of the two-cell stage was thus capable +of performing the morphogenetical process in its totality, +it became, of course, <em>impossible</em> 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.</p> + +<p><span class="pagenum" title="62"><a name="Page_62" id="Page_62"></a></span></p> + +<p>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 +<em>nuclear</em> divisions in <span class="nowrap">morphogenesis?<a name="FNanchor_16_16" id="FNanchor_16_16"></a><a href="#Footnote_16_16" class="fnanchor">16</a></span></p> + +<p>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<span class="pagenum" title="63"><a name="Page_63" id="Page_63"></a></span> +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.</p> + +<p>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.</p> + +<p>We are not, however, studying these things for +cytological, but for morphogenetical purposes, and for these<span class="pagenum" title="64"><a name="Page_64" id="Page_64"></a></span> +the cleavage phenomenon itself is less important than the +organogenetic result of it: all our subjects resulted in +<em>absolutely normal</em> 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 <em>cannot</em> +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<span class="pagenum" title="65"><a name="Page_65" id="Page_65"></a></span> +(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.</p> + +<div class="figcenter" style="width: 444px;"> +<img src="images/fig06.jpg" width="444" height="250" alt="" /> +<p><span class="smcap">Fig. 6.—Pressure-experiments on Echinus.</span></p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a</i><sub>1</sub> and <i>b</i><sub>1</sub>.</td><td class="tal ti">Two normal cleavage stages, consisting of eight and sixteen cells.</td></tr> +<tr><td class="tar vat"><i>a</i><sub>2</sub> and <i>b</i><sub>2</sub>.</td><td class="tal ti">Corresponding stages modified by exerting pressure until the eight-cell stage was finished. See text.</td></tr> +</table> +</div> + +<p>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 <span class="nowrap">result.<a name="FNanchor_17_17" id="FNanchor_17_17"></a><a href="#Footnote_17_17" class="fnanchor">17</a></span></p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">ON THE INTIMATE STRUCTURE OF THE PROTOPLASM OF THE +GERM</span></p> + +<p>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.</p> + +<p>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 <span class="nowrap">1893,<a name="FNanchor_18_18" id="FNanchor_18_18"></a><a href="#Footnote_18_18" class="fnanchor">18</a></span> to urge the hypothesis that there<span class="pagenum" title="66"><a name="Page_66" id="Page_66"></a></span> +existed, that there <em>must</em> 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 <span class="nowrap">magnets.<a name="FNanchor_19_19" id="FNanchor_19_19"></a><a href="#Footnote_19_19" class="fnanchor">19</a></span> +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.</p> + +<p>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 <span class="nowrap">together,<a name="FNanchor_20_20" id="FNanchor_20_20"></a><a href="#Footnote_20_20" class="fnanchor">20</a></span> 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<span class="pagenum" title="67"><a name="Page_67" id="Page_67"></a></span> +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.</p> + +<p>The hypothesis of the morphogenetic importance of +<em>protoplasm</em> 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.</p> + +<p>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, <i>viz.</i>, 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 +<span class="nowrap">Morgan,<a name="FNanchor_21_21" id="FNanchor_21_21"></a><a href="#Footnote_21_21" class="fnanchor">21</a></span> 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<span class="pagenum" title="68"><a name="Page_68" id="Page_68"></a></span> +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>i.e.</i> of a form +which belongs to the other class of Amphibia, after a +separation of <em>any</em> kind, <em>always</em> develop as wholes, their +faculty of regulation being obligatory, like that of Echinus.</p> + +<p>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, <i>x</i>, <i>y</i>, and <i>z</i>, 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 <i>y</i>, by minus <i>y</i>, 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.<span class="pagenum" title="69"><a name="Page_69" id="Page_69"></a></span> +But if regulation has restored, on a smaller scale, the whole +of the arrangement according to all values of <i>x</i>, <i>y</i> and <i>z</i>, +development also can take place completely (Fig. 7).</p> + +<div class="figcenter" style="width: 368px;"> +<img src="images/fig07.jpg" width="368" height="383" alt="" /> +<p><span class="smcap">Fig. 7.—Diagram illustrating the intimate Regulation of Protoplasm from +“Half” to “Whole.”</span></p> + +<p>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 (+<i>y</i>) 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.</p> +</div> + +<p>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<span class="pagenum" title="70"><a name="Page_70" id="Page_70"></a></span> +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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">ON SOME SPECIFICITIES OF ORGANISATION IN CERTAIN GERMS</span></p> + +<p>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 <i class="biological-name">Nereis</i> 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 <span class="nowrap">mollusc.<a name="FNanchor_22_22" id="FNanchor_22_22"></a><a href="#Footnote_22_22" class="fnanchor">22</a></span> The +egg of this form contains a special sort of protoplasm near<span class="pagenum" title="71"><a name="Page_71" id="Page_71"></a></span> +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, <em>and +that special part of the protoplasm contained no nucleus</em>.</p> + +<div class="figcenter" style="width: 376px;"> +<img src="images/fig08.jpg" width="376" height="185" alt="" /> +<p><span class="smcap">Fig. 8.—The Mollusc Dentalium</span> (<em>after</em> E. B. Wilson).</p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a.</i></td><td class="tal ti">The egg, consisting of three different kinds of protoplasmatic material.</td></tr> +<tr><td class="tar vat"><i>b.</i></td><td class="tal ti">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.</td></tr> +</table> +</div> + + +<p class="tac pt12b02em"><span class="lowercase smcap">GENERAL RESULTS OF THE FIRST PERIOD OF +“ENTWICKELUNGSMECHANIK”</span></p> + +<p>This experiment of Crampton’s, afterwards confirmed by +Wilson himself, may be said to have closed the first period<span class="pagenum" title="72"><a name="Page_72" id="Page_72"></a></span> +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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="73"><a name="Page_73" id="Page_73"></a></span> +what has been ascertained about them in the different +classes of the animal kingdom. A full regulation of the +<em>intimate</em> 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 <i class="biological-name">Urodela</i>); it +is facultative only among the other class of Amphibia, the +<i class="biological-name">Anura</i>, and seems to be only partly developed or to be +wanting altogether among ctenophora, ascidia, annelids, +and mollusca. Peculiarities in the organisation of <em>specific +parts</em> 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.</p> + +<p>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 +<span class="nowrap">protoplasm.<a name="FNanchor_23_23" id="FNanchor_23_23"></a><a href="#Footnote_23_23" class="fnanchor">23</a></span> 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.</p> + +<p>That such an endeavour will probably be not without +success, is clear, I should think, from the mere fact that<span class="pagenum" title="74"><a name="Page_74" id="Page_74"></a></span> +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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">SOME NEW RESULTS CONCERNING RESTITUTIONS</span></p> + +<p>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 <em>one</em> typical part of the body in every case,<span class="pagenum" title="75"><a name="Page_75" id="Page_75"></a></span> +but in which the whole of the morphogenetic action to be +performed is transferred in its <em>single</em> parts to the <em>single</em> +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.</p> + +<p>And now we shall pass on to our positive work.</p> + +<p>We shall try to sketch the outlines of what might +properly be called an <em>analytical theory of morphogenesis</em>; +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.</p> + +<p><span class="pagenum" title="76"><a name="Page_76" id="Page_76"></a></span></p> + + +<h4 class="fs120">2. <span class="smcap">Analytical Theory of Morphogenesis</span><a name="FNanchor_24_24" id="FNanchor_24_24"></a><a href="#Footnote_24_24" class="fnanchor">24</a></h4> + +<h5 class="fs120 mb05em">α. <span class="lowercase smcap">THE DISTRIBUTION OF MORPHOGENETIC POTENCIES</span></h5> + +<p class="tac pt12b02em"><i>Prospective Value and Prospective Potency</i></p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="77"><a name="Page_77" id="Page_77"></a></span> +future actual course of this development, whether it be +undisturbed or disturbed in any way; it is, so to say, the +actual, <em>the real fate</em> 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 <em>prospective +value</em> (“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>i.e.</i> is it unchangeable, can it be nothing +but one; or is it variable, may it change according to +different circumstances?</p> + +<p>We first introduce a second concept: the term <em>prospective +potency</em> (“prospective Potenz” in German) of each embryonic +element. The term “prospective morphogenetic potency” is +to signify the <em>possible fate</em> 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?</p> + +<p>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.</p> + +<p><span class="pagenum" title="78"><a name="Page_78" id="Page_78"></a></span></p> + +<p>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.</p> + +<p>As the introductory experiments about “Entwickelungsmechanik” +have shown already that the prospective potency +of embryonic parts, at least in certain cases, <em>can</em> 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 <em>problems</em> of the physiology of form.</p> + +<p>If at each point of the germ something else <em>can</em> 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.</p> + +<p><span class="pagenum" title="79"><a name="Page_79" id="Page_79"></a></span></p> + +<p>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?</p> + +<p>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.</p> + +<p class="tac pt12b02em"><i>The Potencies of the Blastomeres</i></p> + +<p>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 <span class="nowrap">halves.<a name="FNanchor_25_25" id="FNanchor_25_25"></a><a href="#Footnote_25_25" class="fnanchor">25</a></span> We may formulate +this result in the words: the prospective potency of the<span class="pagenum" title="80"><a name="Page_80" id="Page_80"></a></span> +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.</p> + +<p>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.”</p> + +<p>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 +<span class="nowrap">different.<a name="FNanchor_26_26" id="FNanchor_26_26"></a><a href="#Footnote_26_26" class="fnanchor">26</a></span> 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.</p> + +<p class="tac pt12b02em"><i>The Potencies of Elementary Organs in General</i></p> + +<p>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<span class="pagenum" title="81"><a name="Page_81" id="Page_81"></a></span> +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.</p> + +<p>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).</p> + +<div class="figcenter" style="width: 340px;"> +<img src="images/fig09.jpg" width="340" height="583" alt="" /> +<p><span class="smcap">Fig. 9.—The Starfish</span>, <i class="biological-name">Asterias</i>.</p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a</i><sup>1</sup>.</td><td class="tal ti pt02em">Normal gastrula; may be bisected along the main axis or at right angles to it (see dotted lines).</td></tr> +<tr><td class="tar vat"><i>a</i><sup>2</sup>.</td><td class="tal ti pt02em">Normal larva, “<i class="biological-name">Bipinnaria</i>.”</td></tr> +<tr><td class="tar vat"><i>b</i><sup>1</sup>.</td><td class="tal ti pt02em">Small but whole gastrula that results by a process of regulation from the parts of a bisected gastrula.</td></tr> +<tr><td class="tar vat"><i>b</i><sup>2</sup>.</td><td class="tal ti">Small <em>but whole</em> “<i class="biological-name">Bipinnaria</i>,” developed out of <i>b</i><sup>1</sup>.</td></tr> +</table> +</div> + +<p>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.</p> + +<p>And so we may summarise both our last results by<span class="pagenum hide" title="82"><a name="Page_82" id="Page_82"></a></span><br /><span class="pagenum" title="83"><a name="Page_83" id="Page_83"></a></span> +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.</p> + +<p class="tac pt12b02em"><i>Explicit and Implicit Potencies: Primary and Secondary +Potencies</i></p> + +<p>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.</p> + +<p>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 <em>restricted</em>: +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.</p> + +<p><span class="pagenum" title="84"><a name="Page_84" id="Page_84"></a></span></p> + +<p>A few new terms will serve to state a little more +accurately what happens. Of course, with regard to all +morphogenesis which goes on <em>immediately</em> 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 <em>explicit</em>, 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 <em>implicit</em> 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.</p> + +<p>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 <em>primary</em> potencies in our present considerations, +<i>i.e.</i> 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 <em>secondary</em> +or restitutive type have been aroused by our operations; +nothing happened except on the usual lines of organogenesis.<span class="pagenum" title="85"><a name="Page_85" id="Page_85"></a></span> +It is true, some sort of regulation occurred, but that is +included among the factors of ontogeny proper.</p> + +<p>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.</p> + +<p class="tac pt12b02em"><i>The Morphogenetic Function of Maturation in the Light of +Recent Discoveries</i></p> + +<p>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 <span class="nowrap">belongs,<a name="FNanchor_27_27" id="FNanchor_27_27"></a><a href="#Footnote_27_27" class="fnanchor">27</a></span> <i>i.e.</i> 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<span class="pagenum" title="86"><a name="Page_86" id="Page_86"></a></span> +for the formation of typical organs only, without any +regulability.</p> + +<p>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.</p> + +<p>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 <em>earlier</em> 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. <span class="nowrap">Wilson<a name="FNanchor_28_28" id="FNanchor_28_28"></a><a href="#Footnote_28_28" class="fnanchor">28</a></span> that +science owes a proper and definitive elucidation of the<span class="pagenum" title="87"><a name="Page_87" id="Page_87"></a></span> +whole subject. Wilson’s researches, pursued not only by +descriptive <span class="nowrap">methods,<a name="FNanchor_29_29" id="FNanchor_29_29"></a><a href="#Footnote_29_29" class="fnanchor">29</a></span> 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.</p> + +<p>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.</p> + +<p>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 +<em>to mere differences in the time of the beginning of real +morphogenesis</em>. 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 <em>every</em> sort of egg an +<em>earliest</em> stage, in which all parts of its protoplasm are<span class="pagenum" title="88"><a name="Page_88" id="Page_88"></a></span> +equal as to their prospectivity, and in which there are no +potential diversities or restrictions of any kind.</p> + +<p>So much for differences in the <em>real material</em> organisation +of the germ and their bearing on inequipotentialities of the +cleavage cells.</p> + +<p class="tac pt12b02em"><i>The Intimate Structure of Protoplasm: Further Remarks</i></p> + +<p>Where a typical half- or quarter-development from +isolated blastomeres happens to occur, we know already +that the impossibility of a regulation of the <em>intimate polar-bilateral</em> +structure may account for it. As this impossibility +of regulation probably rests on rather simple physical <span class="nowrap">conditions<a name="FNanchor_30_30" id="FNanchor_30_30"></a><a href="#Footnote_30_30" class="fnanchor">30</a></span> +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<span class="pagenum" title="89"><a name="Page_89" id="Page_89"></a></span> +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.</p> + +<p class="tac pt12b02em"><i>The Neutrality of the Concept of “Potency”</i></p> + +<p>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.</p> + + +<h5 class="fs120 mb05em">β. <span class="lowercase smcap">THE “MEANS” OF MORPHOGENESIS</span></h5> + +<p>We now proceed to an analysis of what may properly +be called the <em>means</em> of morphogenesis, the word <span class="pagenum" title="90"><a name="Page_90" id="Page_90"></a></span>“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.</p> + +<h6 class="fs110 mb05em">β′. <i>The Internal Elementary Means of Morphogenesis</i></h6> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="91"><a name="Page_91" id="Page_91"></a></span> +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.</p> + +<p><i>Some Remarks on the Importance of Surface Tension in +Morphogenesis.</i>—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 <span class="nowrap">Berthold<a name="FNanchor_31_31" id="FNanchor_31_31"></a><a href="#Footnote_31_31" class="fnanchor">31</a></span> +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 <span class="nowrap">Bütschli<a name="FNanchor_32_32" id="FNanchor_32_32"></a><a href="#Footnote_32_32" class="fnanchor">32</a></span> 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<span class="pagenum" title="92"><a name="Page_92" id="Page_92"></a></span> +kind of outside pressure, the so-called tissue tension, may +account for the arrangement in surfaces <em>minimae areae</em>. +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.</p> + +<p>It seems, from the researches of <span class="nowrap">Dreyer,<a name="FNanchor_33_33" id="FNanchor_33_33"></a><a href="#Footnote_33_33" class="fnanchor">33</a></span> 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.</p> + +<p>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.</p> + +<p>All indeed that has been described may be said to +belong, in the broadest meaning of the word, to what is<span class="pagenum" title="93"><a name="Page_93" id="Page_93"></a></span> +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.</p> + +<p>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 <span class="nowrap">cause.<a name="FNanchor_34_34" id="FNanchor_34_34"></a><a href="#Footnote_34_34" class="fnanchor">34</a></span></p> + +<p>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 <em>used</em> by life; let it +remain an open question, for the present, how the phenomenon +of “life” is to be regarded in <span class="nowrap">general.<a name="FNanchor_35_35" id="FNanchor_35_35"></a><a href="#Footnote_35_35" class="fnanchor">35</a></span></p> + +<p><i>On Growth</i>.—Among the internal morphogenetical means +which are of a so-called physiological character, that is, +which nobody claims to understand physically at present,<span class="pagenum" title="94"><a name="Page_94" id="Page_94"></a></span> +there is in the first place <em>growth</em>, which must be regarded +as a very essential one.</p> + +<p>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.</p> + +<p>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.</p> + +<p><i>On Cell-division.</i>—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,<span class="pagenum" title="95"><a name="Page_95" id="Page_95"></a></span> +that the same conclusion can be drawn from all our +experiments on very young stages of the germ.</p> + +<p>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.</p> + + +<h6 class="fs110 mb05em">β″. <i>The External Means of Morphogenesis</i></h6> + +<p>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.</p> + +<p>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.</p> + +<p>Within the limits of this minimum and this maximum<span class="pagenum" title="96"><a name="Page_96" id="Page_96"></a></span> +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.</p> + +<p>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 <em>is</em> a very close dependence +of morphogenesis on the outside factors, lest we should be +accused afterwards of having overlooked it.</p> + +<p>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 +<span class="nowrap">investigation.<a name="FNanchor_36_36" id="FNanchor_36_36"></a><a href="#Footnote_36_36" class="fnanchor">36</a></span></p> + +<p><i>The Discoveries of Herbst.</i>—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<span class="pagenum" title="97"><a name="Page_97" id="Page_97"></a></span> +require to be described here a little more fully. All these +researches, which have been carried out almost exclusively +by <span class="nowrap">Herbst,<a name="FNanchor_37_37" id="FNanchor_37_37"></a><a href="#Footnote_37_37" class="fnanchor">37</a></span> 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.</p> + +<p>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<span class="pagenum" title="98"><a name="Page_98" id="Page_98"></a></span> +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.</p> + +<p>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<sub>4</sub>, 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.</p> + +<p>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<span class="pagenum" title="99"><a name="Page_99" id="Page_99"></a></span> +salts of lithium effect radical changes in <span class="nowrap">development.<a name="FNanchor_38_38" id="FNanchor_38_38"></a><a href="#Footnote_38_38" class="fnanchor">38</a></span> 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.</p> + + +<h5 class="fs120 mb05em">γ. <span class="lowercase smcap">THE FORMATIVE CAUSES OR STIMULI</span></h5> + +<p class="tac pt12b02em"><i>The Definition of Cause</i></p> + +<p>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.<span class="pagenum" title="100"><a name="Page_100" id="Page_100"></a></span> +They claim to express completely by an equation all that +is discoverable about any sort of phenomena constantly +connected.</p> + +<p>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 <em>have</em> the concept of the acting “cause” +in our Ego and are <em>forced</em> 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.</p> + +<p>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 <i lang="la" xml:lang="la">causa aequat effectum</i>. 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<span class="pagenum" title="101"><a name="Page_101" id="Page_101"></a></span> +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?</p> + +<p>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.</p> + +<p>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 <em>localisation</em>, whether its specific character also +partly depends on this “cause” or <span class="nowrap">not.<a name="FNanchor_39_39" id="FNanchor_39_39"></a><a href="#Footnote_39_39" class="fnanchor">39</a></span></p> + +<p>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:<span class="pagenum" title="102"><a name="Page_102" id="Page_102"></a></span> +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.</p> + +<p>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.</p> + +<p class="tac pt12b02em"><i>Some Instances of Formative and Directive Stimuli</i></p> + +<p>Again it is to Herbst that we owe not only a very +thorough logical analysis of what he calls “formative and +directive <span class="nowrap">stimuli”<a name="FNanchor_40_40" id="FNanchor_40_40"></a><a href="#Footnote_40_40" class="fnanchor">40</a></span> but also some important discoveries +on this subject. We cannot do more here than barely +mention some of the most characteristic facts.</p> + +<p>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 <span class="nowrap">work<a name="FNanchor_41_41" id="FNanchor_41_41"></a><a href="#Footnote_41_41" class="fnanchor">41</a></span> as morphogenetic causes, though<span class="pagenum" title="103"><a name="Page_103" id="Page_103"></a></span> +most of the typical architecture of hydroid colonies certainly +is due to internal causes, as is also much of the organisation +in plants.</p> + +<p>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.</p> + +<p>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 +<i lang="la" xml:lang="la">a priori</i>, 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.</p> + +<p>Heliotropism and geotropism are among the well-known<span class="pagenum" title="104"><a name="Page_104" id="Page_104"></a></span> +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.</p> + +<p>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 <span class="nowrap">primordia,<a name="FNanchor_42_42" id="FNanchor_42_42"></a><a href="#Footnote_42_42" class="fnanchor">42</a></span> 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.</p> +<p><span class="pagenum" title="105"><a name="Page_105" id="Page_105"></a></span></p> +<p>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.</p> + +<p>But formative dependence of parts may also be of +different types.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="106"><a name="Page_106" id="Page_106"></a></span> +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.</p> + +<p>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.</p> + +<p>And so we may close this <span class="nowrap">section<a name="FNanchor_43_43" id="FNanchor_43_43"></a><a href="#Footnote_43_43" class="fnanchor">43</a></span> on formative stimuli<span class="pagenum" title="107"><a name="Page_107" id="Page_107"></a></span> +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 <span class="nowrap">sex,<a name="FNanchor_44_44" id="FNanchor_44_44"></a><a href="#Footnote_44_44" class="fnanchor">44</a></span> 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 <span class="nowrap">proper<a name="FNanchor_45_45" id="FNanchor_45_45"></a><a href="#Footnote_45_45" class="fnanchor">45</a></span>: 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 <span class="nowrap">chromatin.<a name="FNanchor_46_46" id="FNanchor_46_46"></a><a href="#Footnote_46_46" class="fnanchor">46</a></span></p> + + +<h5 class="fs120 mb05em">δ. <span class="lowercase smcap">THE MORPHOGENETIC HARMONIES</span></h5> + +<p>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.</p> + +<p>But it is far from being true that the development of +each embryonic part depends on the existence or development +of every other one.</p> + +<p>On the contrary, it is a very important and fundamental +feature of organogenesis that it occurs in separate lines,<span class="pagenum" title="108"><a name="Page_108" id="Page_108"></a></span> +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, <i>A</i>, shows the phenomenon of self-differentiation: +this means that the further development of <i>A</i> +is not dependent on certain other parts, <i>B</i>, <i>C</i>, and <i>D</i>; it does +<em>not</em> mean at all that <i>A</i> has not been formatively dependent +on some other parts, <i>E</i> or <i>F</i> at the time of its first appearance, +nor does it imply that there might not be many +formative actions among the constituents of <i>A</i> itself.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 225px;"> +<img src="images/fig10.jpg" width="225" height="208" alt="" /></div> +<div class="figcenter" style="width: 250px;"> +<p><span class="smcap">Fig. 10.—Pluteus-larva of Sphaerechinus.</span></p> +<p>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.</p> +</div> + +<p>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 result<span class="pagenum" title="109"><a name="Page_109" id="Page_109"></a></span>ing +organism is one whole in organisation and in function, +some sort of <em>harmony of constellation</em>, 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.</p> + +<p>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 <em>causal harmony</em>; the term simply expresses the<span class="pagenum" title="110"><a name="Page_110" id="Page_110"></a></span> +unfailing relative condition of formative causes and cause-recipients.</p> + +<p>Finally, in <em>functional harmony</em> 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 <em>threefold harmony</em> among its parts.</p> + + +<h5 class="fs120 mb05em">ε. <span class="lowercase smcap">ON RESTITUTIONS</span><a name="FNanchor_47_47" id="FNanchor_47_47"></a><a href="#Footnote_47_47" class="fnanchor">47</a></h5> + +<p>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.</p> + +<p class="tac pt12b02em"><i>A few Remarks on Secondary Potencies and on Secondary +Morphogenetic Regulations in General</i></p> + +<p>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<span class="pagenum" title="111"><a name="Page_111" id="Page_111"></a></span> +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.</p> + +<p>Primary ontogenetic processes founded upon primary +potencies may <em>imply</em> 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.</p> + +<p>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<span class="pagenum" title="112"><a name="Page_112" id="Page_112"></a></span> +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 <span class="nowrap">removed.<a name="FNanchor_48_48" id="FNanchor_48_48"></a><a href="#Footnote_48_48" class="fnanchor">48</a></span> 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.</p> + +<p>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.</p> + +<p>Such generalisations as are possible about the distribution +of complex potencies are reserved for a special part +of our future discussion.</p> + +<p>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<span class="pagenum" title="113"><a name="Page_113" id="Page_113"></a></span> +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.</p> + +<p class="tac pt12b02em"><i>The Stimuli of Restitutions</i><a name="FNanchor_49_49" id="FNanchor_49_49"></a><a href="#Footnote_49_49" class="fnanchor">49</a></p> + +<p>But now we turn to the important question: what is +the precise <span class="nowrap">stimulus<a name="FNanchor_50_50" id="FNanchor_50_50"></a><a href="#Footnote_50_50" class="fnanchor">50</a></span> that calls forth processes of restitution; +or, in other words, what must have happened in order +that restitution may occur?</p> + +<p>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<span class="pagenum" title="114"><a name="Page_114" id="Page_114"></a></span> +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 <span class="nowrap">impossible.<a name="FNanchor_51_51" id="FNanchor_51_51"></a><a href="#Footnote_51_51" class="fnanchor">51</a></span></p> + +<p>But where then is the stimulus to be found? There +is another rather simple theory of the “Auslösung” of +<span class="nowrap">restitutions,<a name="FNanchor_52_52" id="FNanchor_52_52"></a><a href="#Footnote_52_52" class="fnanchor">52</a></span> 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 <em>new</em> formations may arise +in order to restore a damaged part, or that the latter may +be regenerated in its proper way. For <em>merely quantitative</em> +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 <em>qualitative</em> 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 <span class="nowrap">hypertrophy,<a name="FNanchor_53_53" id="FNanchor_53_53"></a><a href="#Footnote_53_53" class="fnanchor">53</a></span> it is at least doubtful,<span class="pagenum" title="115"><a name="Page_115" id="Page_115"></a></span> +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 <em>afterwards</em> there is a change +in the direction of the nourishing fluids.</p> + +<p>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 <span class="nowrap">not.<a name="FNanchor_54_54" id="FNanchor_54_54"></a><a href="#Footnote_54_54" class="fnanchor">54</a></span> There could hardly be a better +demonstration of the fundamental fact that food assists +restitution, but does not “cause” it in any way.</p> + +<p>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; <i>e.g.</i> 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<span class="pagenum" title="116"><a name="Page_116" id="Page_116"></a></span> +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 <span class="nowrap">sap.<a name="FNanchor_55_55" id="FNanchor_55_55"></a><a href="#Footnote_55_55" class="fnanchor">55</a></span> +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 <span class="nowrap">duty.<a name="FNanchor_56_56" id="FNanchor_56_56"></a><a href="#Footnote_56_56" class="fnanchor">56</a></span></p> + +<p>But I see quite well that such a theory is very little<span class="pagenum" title="117"><a name="Page_117" id="Page_117"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="118"><a name="Page_118" id="Page_118"></a></span></p> + + +<h4 class="fs120">3. <span class="smcap">The Problem of Morphogenetic Localisation</span></h4> + +<h5 class="fs120 mb05em">α. <span class="lowercase smcap">THE THEORY OF THE HARMONIOUS-EQUIPOTENTIAL SYSTEM<br /> +FIRST PROOF OF THE AUTONOMY OF LIFE</span></h5> + +<p>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.</p> + + +<p class="tac pt12b02em"><i>The General Problem</i></p> + +<p>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?</p> + +<p>All of these questions are apt to lead us to further<span class="pagenum" title="119"><a name="Page_119" id="Page_119"></a></span> +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.</p> + +<p>But if the answer were a negative one? What would +that suggest?</p> + +<p>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.</p> + +<p>But what are we to say if even the preliminary analysis, +which possibly might lead to such an ultimate result, fails?</p> + +<p>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 <em>localisation</em> +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?</p> + + +<p class="tac pt12b02em"><i>The Morphogenetic “System”</i></p> + +<p>We know from our experimental work that many, if +not all, of the elementary organs in ontogeny show one<span class="pagenum" title="120"><a name="Page_120" id="Page_120"></a></span> +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 “<em>system</em>,” 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 <em>equipotential systems</em>.</p> + +<p>But such a term would not altogether indicate the real +character of these systems.</p> + +<p>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 <em>whole</em>, 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.</p> + +<p>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 <em>single</em> part in the totality of what<span class="pagenum" title="121"><a name="Page_121" id="Page_121"></a></span> +will occur in the whole system; it is to this <em>single</em> 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.</p> + +<p>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 <span class="nowrap">morphogenesis,<a name="FNanchor_57_57" id="FNanchor_57_57"></a><a href="#Footnote_57_57" class="fnanchor">57</a></span> 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 <em>real +products</em> of our systems. The term <em>harmonious-equipotential +system</em> therefore seems to be the right one to denote them.</p> + +<p>We now shall try first to analyse to its very extremes +the meaning of the statement that a morphogenetic system +is harmonious-equipotential.</p> + +<p><span class="pagenum" title="122"><a name="Page_122" id="Page_122"></a></span></p> + + +<p class="tac pt12b02em"><i>The “Harmonious-Equipotential System”</i></p> + +<p>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.</p> + +<p>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, <i>a</i> and <i>b</i>. And now we have all +the means necessary for the analytical study of the differentiation +of an harmonious-equipotential system.</p> + +<p>Our plane of the dimensions <i>a</i> and <i>b</i> 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 +<i>x</i> and of <i>y</i>. 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?</p> + +<p><span class="pagenum" title="123"><a name="Page_123" id="Page_123"></a></span></p> + +<p>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> + +<p class="tac nowrap"> +<i>p.v. (X) = f( . . . )</i><br /> +</p> + +<p><i>i.e.</i> “the prospective value of the element <i>X</i> is a function +of . . .”—of what?</p> + +<p>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 <em>absolute +size</em> of the actually existing part of our system in the +particular case. Let <i>s</i> be the absolute size of the system +in any actual experimental case of morphogenesis: then we +may write <span class="nowrap"><i>p.v. (X) = f(s . . . )</i></span>. But we shall have to add +still some other letter to this <i>s</i>.</p> + +<p>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 <i>a<sub>1</sub> b<sub>1</sub></i>, and at another time an equal +amount of it which has the lines <i>a<sub>2</sub> b<sub>2</sub></i> 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<span class="pagenum" title="124"><a name="Page_124" id="Page_124"></a></span> +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, <i>X</i>, 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, <i>a</i> and <i>b</i>; let this actual position be expressed +by the letter <i>l</i>, <i>l</i> marking the distance of <span class="nowrap">one<a name="FNanchor_58_58" id="FNanchor_58_58"></a><a href="#Footnote_58_58" class="fnanchor">58</a></span> of the actual +boundary lines of our piece from <i>a</i> or <i>b</i>: then we are entitled +to improve our formula by writing <span class="nowrap"><i>p.v. (X) = f(s, l . . . )</i></span> +(Fig. 11).</p> + +<div class="figcenter" style="width: 440px;"> +<img src="images/fig11.jpg" width="440" height="276" alt="" /> +<p><span class="smcap">Fig. 11.—Diagram to show the Characteristics of an +“Harmonious-equipotential System</span>.”</p> + +<p class="ml0em">The element <i>X</i> forms part of the systems <i>a b</i> or <i>a<sub>1</sub> b<sub>1</sub></i> or <i>a<sub>2</sub> b<sub>2</sub></i>; its prospective value is +different in each case.</p> +</div> + +<p>But the formula is not yet complete: <i>s</i> and <i>l</i> are what +the mathematicians call variables: they may have any +actual value and there will always be a definite value of <i>p.v.</i>, +<i>i.e.</i> of the actual fate which is being considered; to every +value of <i>s</i> and <i>l</i>, 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 <em>not</em> 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.</p> + +<p>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<span class="pagenum" title="125"><a name="Page_125" id="Page_125"></a></span> +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 <em>non-variable</em> 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 <i>E</i>, we are now able to complete our +formula by saying <span class="nowrap"><i>p.v. (X) = f(s, l, E)</i></span>.</p> + +<p>So far the merely analytical study of the differentiation +of harmonious-equipotential <span class="nowrap">systems.<a name="FNanchor_59_59" id="FNanchor_59_59"></a><a href="#Footnote_59_59" class="fnanchor">59</a></span></p> +<p><span class="pagenum" title="126"><a name="Page_126" id="Page_126"></a></span></p> + +<p class="tac pt12b02em"><i>Instances of “Harmonious-Equipotential Systems”</i></p> + +<p>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 <em>single</em> part of the +truncated organism left by the operation has to perform +one <em>single</em> act of restoration, the full restitution being the +result of the totality of all. These cases must now be +submitted to a full analysis.</p> + +<p>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. <i class="biological-name">Tubularia</i> 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 +<i class="biological-name">Tubularia</i> 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<span class="pagenum" title="127"><a name="Page_127" id="Page_127"></a></span> +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 <i class="biological-name">Tubularia</i> +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 <i class="biological-name">Tubularia</i>: 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 <i class="biological-name">Tubularia</i> 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.</p> + +<p>The figures will serve to show you a little more concretely +what has been described. The head of <i class="biological-name">Tubularia</i> +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<span class="pagenum" title="128"><a name="Page_128" id="Page_128"></a></span> +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 <i>e</i>, and <i>g</i>, you easily find out +that the absolute lengths of the two tentacle rings are very +different, and that both are in <span class="nowrap">proportion<a name="FNanchor_60_60" id="FNanchor_60_60"></a><a href="#Footnote_60_60" class="fnanchor">60</a></span> to the actual size +of the stem (Fig. 12).</p> + +<div class="figcenter" style="width: 495px;"> +<img src="images/fig12.jpg" width="495" height="311" alt="" /> +<p><span class="smcap">Fig. 12.—Tubularia.</span></p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a.</i></td><td class="tal ti">Diagram of the “Hydranth,” with its short and long tentacles.</td></tr> +<tr><td class="tar vat"><i>b.</i></td><td class="tal ti">Restitution of a new hydranth inside the perisarc (<i>p</i>).</td></tr> +<tr><td class="tar vat"><i>c.</i></td><td class="tal ti">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 ↑.</td></tr> +<tr><td class="tar vat"><i>d.</i></td><td class="tal ti">A stem of <i class="biological-name">Tubularia</i> cut either at <i>a<sub>1</sub>b<sub>1</sub></i> or at <i>a<sub>2</sub>b<sub>2</sub></i> or at <i>a<sub>1</sub>c</i>.</td></tr> +<tr><td class="tar vat"><i>e.</i></td><td class="tal ti">Position of tentacles in the piece cut at <i>a<sub>1</sub>b<sub>1</sub></i>.</td></tr> +<tr><td class="tar vat"><i>f.</i></td><td class="tal ti">Position of tentacles in the piece cut at <i>a<sub>2</sub>b<sub>2</sub></i> which is equal in length to <i>a<sub>1</sub>b<sub>1</sub></i>.</td></tr> +<tr><td class="tar vat"><i>g.</i></td><td class="tal ti">Position of tentacles in the piece cut at <i>a<sub>1</sub>c</i>, which is half as long as <i>a<sub>1</sub>b<sub>1</sub></i>.</td></tr> +</table> +</div> + +<p><span class="pagenum" title="129"><a name="Page_129" id="Page_129"></a></span></p> +<p>So we find our formula <span class="nowrap"><i>p.v. (X) = f(s, l, E)</i></span> very well +illustrated in <i class="biological-name">Tubularia</i>. 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 <i>E</i>, <i>i.e.</i> 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.</p> + +<div class="figcenter" style="width: 424px;"> +<img src="images/fig13.jpg" width="424" height="286" alt="" /> +<p><span class="smcap">Fig. 13.—Clavellina.</span></p> +<table class="fs100" border="0" cellpadding="0" cellspacing="0" summary=""> +<tr><td class="tar vat"><i>a. </i></td><td class="tal ti">Diagram of the normal animal: <i>E</i> and <i>J</i> = openings; <i>K</i> = branchial apparatus; <i>D</i> = intestine; <i>M</i> = stomach; <i>H</i> = heart.</td></tr> +<tr><td class="tar vat"><i>b. </i></td><td class="tal ti">The isolated branchial apparatus.</td></tr> +<tr><td class="tar vat"><i>c-e.</i></td><td class="tal ti">Different stages of reduction of the branchial apparatus.</td></tr> +<tr><td class="tar vat"><i>f. </i></td><td class="tal ti">The new <em>whole</em> little ascidian.</td></tr> +</table> +</div> + +<p>Another very typical case of a morphogenetic system +of the harmonious type is supplied by the phenomena of +restoration in the ascidian <i class="biological-name">Clavellina</i>. 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 <i class="biological-name">Clavellina</i> 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 com<span class="pagenum" title="130"><a name="Page_130" id="Page_130"></a></span>plete +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 <em>complete</em> little +<i class="biological-name">Clavellina</i>. 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 +<em>whole</em>, 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.</p> + +<p>We could hardly imagine a better instance of an +harmonious-equipotential system.</p> + +<p>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 +<i class="biological-name">Planaria</i> are very fine examples of them. But to one +special case of harmonious equipotentiality you must allow +me to direct your further attention.</p> + +<p>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<span class="pagenum" title="131"><a name="Page_131" id="Page_131"></a></span> +of regeneration proper, until T. H. Morgan succeeded in +showing that in the genus <i class="biological-name">Stentor</i> it follows just the very +lines which we know already from our study of embryonic +organs or from <i class="biological-name">Tubularia</i>; 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-<span class="pagenum" title="132"><a name="Page_132" id="Page_132"></a></span>equipotential +system may cover a very great area—that, in +fact, it is a scheme of a very wide extent.</p> + + +<p class="tac pt12b02em"><i>The Problem of the Factor</i> E</p> + +<p>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, <span class="nowrap"><i>p.v. (X) = f(s, l, E)</i></span> was the short expression +of all the relations involved; <i>s</i> and <i>l</i>, the absolute +size of the system and the relative position of the element +with respect to some fixed points, were independent variables; +<i>E</i> was a constant, namely, the prospective potency, with +special regard to the proportions embraced by it.</p> + +<p>We shall now study the significance of the factor <i>E</i>.</p> + +<p>What does this <i>E</i> 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 <i>E</i> mean, if it can be shown <em>not</em> to +be a short sign for a mere sum?</p> + + +<p class="tac pt12b02em"><i>No Explanation Offered by “Means” or “Formative Stimuli”</i></p> + +<p>For practical purposes it seems better if we modify the +statement of our question. Let us put it thus: <i>E</i> 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<span class="pagenum" title="133"><a name="Page_133" id="Page_133"></a></span> +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 <span class="nowrap">all.<a name="FNanchor_61_61" id="FNanchor_61_61"></a><a href="#Footnote_61_61" class="fnanchor">61</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="134"><a name="Page_134" id="Page_134"></a></span></p> + + +<p class="tac pt12b02em"><i>No Explanation Offered by a Chemical Theory +of Morphogenesis</i></p> + +<p>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.</p> + +<p>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 <span class="nowrap">contradicts,<a name="FNanchor_62_62" id="FNanchor_62_62"></a><a href="#Footnote_62_62" class="fnanchor">62</a></span> 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 <em>has</em> been completed +once already? And we even know that regeneration may +go on several times running from the same locality!</p> +<p><span class="pagenum" title="135"><a name="Page_135" id="Page_135"></a></span></p> +<p>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?</p> + +<p>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 <i>a</i>, is disintegrated +to the amount of <i>a</i><sub>1</sub>; from <i>a</i><sub>1</sub> are formed the two more +simple compounds, <i>b</i> and <i>c</i>, both of them in definite +quantities; then we have the three chemical individuals, +<i>a-a</i><sub>1</sub>, <i>b</i> and <i>c</i>, 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 <i>b</i> and <i>c</i> respectively, <i>a-a</i><sub>1</sub> 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 +<span class="pagenum" title="136"><a name="Page_136" id="Page_136"></a></span>parts, <i>a-a</i><sub>1</sub>, <i>b</i> and <i>c</i>, 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 <i>a/n</i> +is left; then, of course, the three constituents after the +partial disintegration would be <i>a-a<sub>1</sub>/n</i>, <i>b/n</i> and <i>c/n</i>, and so it +follows that the proportionality of localisation would really +be preserved in any case.</p> + +<p>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 +<em>form</em> 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, <i>e.g.</i> the arrangement of the single<span class="pagenum" title="137"><a name="Page_137" id="Page_137"></a></span> +parts of the skeleton of the hand or foot, but also the +special form of each element is typical, <i>e.g.</i> 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 <span class="nowrap">germ,<a name="FNanchor_63_63" id="FNanchor_63_63"></a><a href="#Footnote_63_63" class="fnanchor">63</a></span> 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.</p> + +<p>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<span class="pagenum" title="138"><a name="Page_138" id="Page_138"></a></span> +assume that would be to go beyond the limits of chemistry +in chemistry itself.</p> + + +<p class="tac pt12b02em"><i>No Machine Possible Inside the Harmonious Systems</i></p> + +<p>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 <i>E</i> of our equation stood for: viz., +a resultant action of many complicated elemental interactions, +and nothing more.</p> + +<p>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 <em>such</em> a machine as <em>he</em> +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?</p> + +<p>We shall understand the word “machine” in a most +general sense. A machine is a typical configuration of<span class="pagenum" title="139"><a name="Page_139" id="Page_139"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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 <i>V</i>. Good! Then there ought to exist a machine, like +that which exists in the whole undisturbed system, in this +portion <i>V</i> also, only of smaller dimensions; but it also<span class="pagenum" title="140"><a name="Page_140" id="Page_140"></a></span> +ought to exist in the portion <i>V</i><sub>1</sub> which is equal to <i>V</i> in +amount, and also in <i>V</i><sub>2</sub>, in <i>V</i><sub>3</sub>, <i>V</i><sub>4</sub> and so on. Indeed, +there do exist almost indefinitely many <i>V</i><sub>n</sub> all of which +can perform the whole morphogenesis, and all of which +therefore ought to possess the machine. But these different +portions <i>V</i><sub>n</sub> are only partly different from each other in +spatial relation. Many parts of <i>V</i><sub>2</sub> are also parts of <i>V</i><sub>1</sub> and +of <i>V</i><sub>3</sub> and of <i>V</i><sub>4</sub> and so on; that is to say, the different +volumes <i>V</i><sub>n</sub> 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.</p> + +<p>A very strange sort of machine indeed, which is the +same in all its parts (Fig. 14)!</p> + +<div class="figcenter" style="width: 448px;"> +<img src="images/fig14.jpg" width="448" height="111" alt="" /> +<p><span class="smcap">Fig. 14.—An “Harmonious-equipotential System” of whatever kind.</span></p> +<p> +According to the “machine-theory” of life this system ought to possess a certain unknown very complicated machine <em>in its completeness</em>:<br /> +<span class="ml27em">(<i>a</i>) in its total length,</span><br /> +<span class="ml1em">and (<i>b</i>) in each of the equal volumes <i>v</i>, <i>v</i><sub>1</sub>, <i>v</i><sub>2</sub>, <i>v</i><sub>3</sub> and so on,</span><br /> +<span class="ml1em">and (<i>c</i>) in each of the unequal volumes <i>w</i>, <i>x</i>, <i>y</i>, and so on,</span><br /> +<span class="ml1em">and (<i>d</i>) in every imaginable volume, no matter of what size.</span><br /> +Therefore the “machine-theory” of life is absurd. +</p> +</div> + +<p>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 <i>V</i><sub>n</sub>, all of the +same size, must possess the hypothetic machine in its +completeness, but that all amounts of the values <i>V</i><sub>n</sub>-<i>n</i>, +<i>n</i> being variable, must possess the totality of the machine +also: and all values <i>V</i><sub>n</sub>-<i>n</i>, with their variable <i>n</i>, may again +overlap each other.</p> + +<p>Here we are led to real absurdities!</p> + +<p><span class="pagenum" title="141"><a name="Page_141" id="Page_141"></a></span></p> + +<p>But what is the conclusion of our rather wild considerations?</p> + +<p>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 <em>must</em> 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. <em>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.</em></p> + +<p>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 <span class="nowrap">rearrange<a name="FNanchor_64_64" id="FNanchor_64_64"></a><a href="#Footnote_64_64" class="fnanchor">64</a></span> its parts at will.</p> + +<p>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.</p> +<p><span class="pagenum" title="142"><a name="Page_142" id="Page_142"></a></span></p> + +<p class="tac pt12b02em"><i>The Autonomy of Morphogenesis Proved</i></p> + +<p>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 <i>E</i> 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 <em>a true element of nature</em>. 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.</p> + +<p>All our results at present, indeed, are negative in their +form; our evidence was throughout what is called <i lang="la" xml:lang="la">per +exclusionem</i>, or indirect or apagogic. There were excluded +from a certain number of possibilities all except one; a +disjunctive proposition was stated in the form: <i>E</i> 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.</p> + +<p>We shall not hesitate to call by its proper name what +we believe we have proved about morphogenetic phenomena.<span class="pagenum" title="143"><a name="Page_143" id="Page_143"></a></span> +What we have proved to be true has always been called +<em>vitalism</em>, 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 <em>autonomy of life</em>, +as proved at least in the field of morphogenesis. I know +very well that the word “autonomy” usually means the +faculty of <em>giving</em> 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 <em>being subjected</em> 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.”</p> + +<p>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.</p> + + +<p class="tac pt12b02em">“<i>Entelechy</i>”</p> + +<p>But shall we not give a name to our vitalistic or +autonomous factor <i>E</i>, concerned in morphogenesis? Indeed +we will, and it was not without design that we chose the +letter <i>E</i> to represent it provisionally. The great father +of systematic philosophy, Aristotle, as many of you will<span class="pagenum" title="144"><a name="Page_144" id="Page_144"></a></span> +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.</p> + +<p>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 <em>Entelechy</em>, though +without identifying our doctrine with what Aristotle meant +by the word <ins title="entelecheia">έντελέχεια</ins>. 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 <ins title="entelecheia">ἐντελέχεια</ins> 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,” <ins title="ho echei en eautô to telos">ὃ ἔχει ἐν ἑαυτᾣ τὸ τέλος</ins>.</p> + +<p>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 +<em>extensive</em> character, but there was something else: there was +entelechy, and thus we may provisionally call entelechy an +“<em>intensive manifoldness</em>.” That then is our result: not +evolutio, but epigenesis—<span class="pagenum" title="145"><a name="Page_145" id="Page_145"></a></span>“epigenesis vitalistica.”</p> + + +<p class="tac pt12b02em"><i>Some General Remarks on Vitalism</i></p> + +<p>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 <span class="nowrap">all-important.<a name="FNanchor_65_65" id="FNanchor_65_65"></a><a href="#Footnote_65_65" class="fnanchor">65</a></span> 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 <em>first proof</em>, which is based +upon the analysis of the <em>differentiation of harmonious-equipotential +systems</em>. 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.</p> + +<p>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<span class="pagenum" title="146"><a name="Page_146" id="Page_146"></a></span> +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.</p> + +<p>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 <span class="nowrap">Noll.<a name="FNanchor_66_66" id="FNanchor_66_66"></a><a href="#Footnote_66_66" class="fnanchor">66</a></span></p> + + +<p class="tac pt12b02em"><i>The Logic of our First Proof of Vitalism</i></p> + +<p>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 <em>proof</em> +of life autonomy.</p> + +<p>Firstly, we have looked upon the phenomena of<span class="pagenum" title="147"><a name="Page_147" id="Page_147"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>And it is not the formal, logical character alone which<span class="pagenum" title="148"><a name="Page_148" id="Page_148"></a></span> +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 +<em>impossible</em>. I refer to the concept of <em>universality</em>. All +concepts about nature which are gained by positive construction +out of elements resulting from analysis, claim to +be of <em>universal validity</em>; without that claim there could +indeed be no science.</p> + +<p>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 +<em>all</em> blastomeres and <em>all</em> stems of <i class="biological-name">Tubularia</i>, including those +upon which we have <em>not</em> carried out our experiments, +will behave like those we have experimented with; and +those concepts also presume that a certain germ of Echinus, +<i>A</i>, the blastomeres of which were not separated, would have +given two whole larvae, if separation had taken place, while +another germ, <i>B</i>, 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.</p> + +<p>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 <em>every</em> law of nature.</p> + +<p><span class="pagenum" title="149"><a name="Page_149" id="Page_149"></a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="150"><a name="Page_150" id="Page_150"></a></span></p> + + +<h4 class="fs120">4. <span class="smcap">On Certain other Features of Morphogenesis +Advocating its Autonomy</span></h4> + +<p>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.</p> + +<p>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<span class="pagenum" title="151"><a name="Page_151" id="Page_151"></a></span> +of our problems of morphogenesis and their solutions, will +be the best preparation for the philosophical part of these +lectures.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">HARMONIOUS-EQUIPOTENTIAL SYSTEMS FORMED BY +WANDERING CELLS</span></p> + +<p>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 <i lang="la" xml:lang="la">in situ</i>. 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<span class="pagenum" title="152"><a name="Page_152" id="Page_152"></a></span> +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.</p> + +<p>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<span class="pagenum" title="153"><a name="Page_153" id="Page_153"></a></span> +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 +<em>order</em> to produce this totality. We <em>are</em> 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 <em>can</em> do every +single act, all of them also <em>can</em> 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.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">ON CERTAIN COMBINED TYPES OF MORPHOGENETIC SYSTEMS</span></p> + +<p>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<span class="pagenum" title="154"><a name="Page_154" id="Page_154"></a></span> +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 <span class="nowrap">stage.<a name="FNanchor_67_67" id="FNanchor_67_67"></a><a href="#Footnote_67_67" class="fnanchor">67</a></span> 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.</p> + +<p>We propose to give the name of <em>mixed-equipotential +systems</em> 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 <i class="biological-name">Clavellina</i> for instance.<span class="pagenum" title="155"><a name="Page_155" id="Page_155"></a></span> +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 <i class="biological-name">Planaria</i> for +instance.</p> + +<p>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 <em>single</em> cross-section is of the +harmonious type, we must speak of <em>complex-harmonious +systems</em>. 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 <i class="biological-name">Planaria</i> 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.</p> + +<p>You may say that our two additions to the theory of<span class="pagenum" title="156"><a name="Page_156" id="Page_156"></a></span> +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.</p> + +<p>While dealing with our harmonious-equipotential systems +as the starting-points of processes of restitution, <i>e.g.</i> in +<i class="biological-name">Tubularia</i>, <i class="biological-name">Clavellina</i>, 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 <em>reciprocity of harmony</em> as existing +between the single tissues or germ layers which constitute +many harmonious-equipotential systems, and there can be<span class="pagenum" title="157"><a name="Page_157" id="Page_157"></a></span> +little doubt that we have here an important feature with +regard to general <span class="nowrap">morphogenesis.<a name="FNanchor_68_68" id="FNanchor_68_68"></a><a href="#Footnote_68_68" class="fnanchor">68</a></span></p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE “MORPHAESTHESIA” OF NOLL</span><a name="FNanchor_69_69" id="FNanchor_69_69"></a><a href="#Footnote_69_69" class="fnanchor">69</a></p> + +<p>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<span class="pagenum" title="158"><a name="Page_158" id="Page_158"></a></span> +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 <span class="nowrap">form-phenomena,<a name="FNanchor_70_70" id="FNanchor_70_70"></a><a href="#Footnote_70_70" class="fnanchor">70</a></span> 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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">RESTITUTIONS OF THE SECOND ORDER</span></p> + +<p>In the hydroid polyp <i class="biological-name">Tubularia</i>, already familiar to us +as being a most typical representative of the harmonious-equipotential +systems, a very interesting phenomenon has +been <span class="nowrap">discovered<a name="FNanchor_71_71" id="FNanchor_71_71"></a><a href="#Footnote_71_71" class="fnanchor">71</a></span>, 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 <i class="biological-name">Tubularia</i>, after an operation, consists in the<span class="pagenum" title="159"><a name="Page_159" id="Page_159"></a></span> +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.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">ON THE “EQUIFINALITY” OF RESTITUTIONS</span><a name="FNanchor_72_72" id="FNanchor_72_72"></a><a href="#Footnote_72_72" class="fnanchor">72</a></p> + +<p>I have told you already that <i class="biological-name">Tubularia</i> in the phenomena +of the regulation of restitutions offers us a second +problem of a great general importance, the problem of +the <em>Equifinality of Restitutions</em>. 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.</p> + +<p><span class="pagenum" title="160"><a name="Page_160" id="Page_160"></a></span></p> + +<p>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.</p> + +<p>This is precisely analogous to the behaviour of our +<i class="biological-name">Tubularia</i>. <i class="biological-name">Tubularia</i> 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 <i lang="la" xml:lang="la">de novo</i> 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<span class="pagenum" title="161"><a name="Page_161" id="Page_161"></a></span> +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.</p> + +<p>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.</p> + +<p>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 <em>same</em> starting-point, which is +decidedly non-typical but atypical, <i>i.e.</i> dependent on our +arbitrary choice, leading by <em>different</em> ways always to the +<em>same</em> end.</p> + +<p>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<span class="pagenum" title="162"><a name="Page_162" id="Page_162"></a></span> +of autonomy, and part in the second one, which is to +follow.</p> + +<p>Another important phenomenon of the equifinality of +regulation was discovered by Morgan. A species of the +flatworm <i class="biological-name">Planaria</i> 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 <span class="nowrap">tip.<a name="FNanchor_73_73" id="FNanchor_73_73"></a><a href="#Footnote_73_73" class="fnanchor">73</a></span> In <i class="biological-name">Tubularia</i> 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.</p> + +<p><i class="biological-name">Clavellina</i> 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.</p> + +<p>The discussion of other instances of equifinality, though<span class="pagenum" title="163"><a name="Page_163" id="Page_163"></a></span> +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.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">REMARKS ON “RETRO-DIFFERENTIATION”</span></p> + +<p>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. +<em>retro-</em> or <em>back-differentiation</em>.<a name="FNanchor_74_74" id="FNanchor_74_74"></a><a href="#Footnote_74_74" class="fnanchor">74</a> We know that it occurs in +<i class="biological-name">Clavellina</i> and in <i class="biological-name">Tubularia</i>; we may add that it also +happens in <i class="biological-name">Hydra</i>, and that in the flatworm <i class="biological-name">Planaria</i> the +pharynx, if it is too large for a piece that is cut out,<span class="pagenum" title="164"><a name="Page_164" id="Page_164"></a></span> +may be differentiated back and be replaced by a new +pharynx, which is smaller.</p> + +<p>It is not death and sloughing of parts that occurs in +these <span class="nowrap">cases,<a name="FNanchor_75_75" id="FNanchor_75_75"></a><a href="#Footnote_75_75" class="fnanchor">75</a></span> 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 +<em>all</em> morphogenesis might be capable perhaps of going +backwards under certain conditions.</p> + +<p>It is important to note that in <span class="nowrap">most<a name="FNanchor_76_76" id="FNanchor_76_76"></a><a href="#Footnote_76_76" class="fnanchor">76</a></span> 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.</p> + +<hr class="short" /> + +<p><span class="pagenum" title="165"><a name="Page_165" id="Page_165"></a></span></p> + + + +<h3><i>C.</i> ADAPTATION</h3> + +<h4 class="fs120"><span class="smcap">Introductory Remarks on Regulations in General</span></h4> + + +<p>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<span class="pagenum" title="166"><a name="Page_166" id="Page_166"></a></span> +distribution regulation is based, and thus we may be said +to have studied some types of regulation more or less +indirectly when analysing potencies.</p> + +<p>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.</p> + +<p>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 <em>restitutions</em>, +while to regulations of functional disturbances we shall +apply the name <em>adaptations</em>. It is with <em>adaptations</em> that we +have to deal in the following.</p> + +<p><span class="pagenum" title="167"><a name="Page_167" id="Page_167"></a></span></p> + +<p>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.</p> + +<p><span class="pagenum" title="168"><a name="Page_168" id="Page_168"></a></span></p> + + +<h4 class="fs120">1. <span class="smcap">Morphological Adaptation</span></h4> + +<p><i>Morphological adaptation</i> 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.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE LIMITS OF THE CONCEPT OF ADAPTATION</span></p> + +<p>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<span class="pagenum" title="169"><a name="Page_169" id="Page_169"></a></span> +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 <em>harmony</em> 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.</p> + +<p>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<span class="pagenum" title="170"><a name="Page_170" id="Page_170"></a></span> +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 <em>cannot</em> 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 <span class="nowrap">many<a name="FNanchor_77_77" id="FNanchor_77_77"></a><a href="#Footnote_77_77" class="fnanchor">77</a></span> 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 <em>in</em> the process of pathological morphogenesis, but +<em>the process</em> itself could hardly be called adaptive.</p> + +<p>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?</p> + +<p>Let us remember what the word adaptation is really to +mean in our discussions: a state of functioning is adapted—<span class="pagenum" title="171"><a name="Page_171" id="Page_171"></a></span>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.</p> + +<p>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 <em>to itself</em>. Our definition stated that a “cause” is +any one of the sum of necessary factors from without that +accounts either for the localisation <em>or</em> for <em>the specification</em> +of the effect, and the definition holds very well in this +case. Indeed, the specification of the effect is determined +<em>by</em> the outside factor in every case of an adaptation <em>to</em> it, +by the mere <em>fact</em> of its being a specific adaptation to this +specific factor.</p> + +<p>We must not forget that in this chapter we are not +studying real individual morphogenesis as the realisation<span class="pagenum" title="172"><a name="Page_172" id="Page_172"></a></span> +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.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">ADAPTATIONS TO FUNCTIONAL CHANGES FROM WITHOUT</span><a name="FNanchor_78_78" id="FNanchor_78_78"></a><a href="#Footnote_78_78" class="fnanchor">78</a></p> + +<p>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<span class="pagenum" title="173"><a name="Page_173" id="Page_173"></a></span> +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.</p> + +<p>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 <em>not</em> directly <em>to</em> the agents of the +medium, but to changes of functional states induced <em>by</em> +those agents; that adaptations only <em>are</em> “adaptations” by +being correctives to the functional state.</p> + +<p><span class="pagenum" title="174"><a name="Page_174" id="Page_174"></a></span></p> + +<p>There simply <em>is</em> an “adaptation” of structure in <em>such</em> +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?</p> + +<p>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.</p> + +<p>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 <em>in</em> the normal connection of processes. We +reserve the title of “secondary adaptations” for cases such +as those described, for instance, by <span class="nowrap">Vöchting,<a name="FNanchor_79_79" id="FNanchor_79_79"></a><a href="#Footnote_79_79" class="fnanchor">79</a></span> where not +merely one and the same tissue originates adaptively with +regard to the degree of its normal functioning, but where<span class="pagenum" title="175"><a name="Page_175" id="Page_175"></a></span> +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 <em>kind</em> 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.</p> + +<p>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 <i class="biological-name">Jussiaea</i> 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.</p> + +<p>Among animals there is only one well-studied instance +of our first type of adaptive morphological characters. +<i class="biological-name">Salamandra atra</i>, 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,<span class="pagenum" title="176"><a name="Page_176" id="Page_176"></a></span> +as was shown in an excellent memoir by <span class="nowrap">Kammerer,<a name="FNanchor_80_80" id="FNanchor_80_80"></a><a href="#Footnote_80_80" class="fnanchor">80</a></span> 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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">TRUE FUNCTIONAL ADAPTATION</span><a name="FNanchor_81_81" id="FNanchor_81_81"></a><a href="#Footnote_81_81" class="fnanchor">81</a></p> + +<p>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.”</p> + +<p>It was Roux who first saw the importance of this kind +of organic regulation and thought it well to give it a distinguishing +name. <em>By functioning the organisation of organic +tissues becomes better adapted for functioning.</em> 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<span class="pagenum" title="177"><a name="Page_177" id="Page_177"></a></span> +kind, when for instance, as shown by <span class="nowrap">Babák,<a name="FNanchor_82_82" id="FNanchor_82_82"></a><a href="#Footnote_82_82" class="fnanchor">82</a></span> 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.</p> + +<p>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 <em>for</em> mechanics, +not <em>by</em> 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.</p> + +<p>But, the merely descriptive facts of mechanical adapted<span class="pagenum" title="178"><a name="Page_178" id="Page_178"></a></span>ness +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.</p> + +<p>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 +<span class="nowrap">correspondences.<a name="FNanchor_83_83" id="FNanchor_83_83"></a><a href="#Footnote_83_83" class="fnanchor">83</a></span></p> + +<p>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<span class="pagenum" title="179"><a name="Page_179" id="Page_179"></a></span> +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 <span class="nowrap">explanation.<a name="FNanchor_84_84" id="FNanchor_84_84"></a><a href="#Footnote_84_84" class="fnanchor">84</a></span> But adaptations +remain adaptations in spite of that; even if they only +deserve the name of “primary” regulations.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THEORETICAL CONCLUSIONS</span></p> + +<p>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<span class="pagenum" title="180"><a name="Page_180" id="Page_180"></a></span> +authors, especially by Klebs, Holmes, and <span class="nowrap">Child:<a name="FNanchor_85_85" id="FNanchor_85_85"></a><a href="#Footnote_85_85" class="fnanchor">85</a></span> 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 <em>for</em> future <span class="nowrap">functioning.<a name="FNanchor_86_86" id="FNanchor_86_86"></a><a href="#Footnote_86_86" class="fnanchor">86</a></span></p> + +<p>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 <em>is</em> a certain kind +of, so to speak, architectonic morphogenesis, both typical and +restitutive, previous to specific functioning altogether.</p> + +<p>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<span class="pagenum" title="181"><a name="Page_181" id="Page_181"></a></span> +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.</p> + +<p>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 +<em>answering</em> 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 <span class="nowrap">Goltz<a name="FNanchor_87_87" id="FNanchor_87_87"></a><a href="#Footnote_87_87" class="fnanchor">87</a></span> 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.</p> + +<p>We only, I believe, can state the fact that there <em>are</em> +relations between morphogenetic causes and effects which +<em>are</em> 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 <em>might</em> 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<span class="pagenum" title="182"><a name="Page_182" id="Page_182"></a></span> +<em>cannot</em> exist in other fields of morphogenesis. But we are +searching for a new and independent proof; and that is +indeed not to be found <span class="nowrap">here.<a name="FNanchor_88_88" id="FNanchor_88_88"></a><a href="#Footnote_88_88" class="fnanchor">88</a></span></p> + +<p>At present it must be taken as one of the fundamental +<em>facts</em> 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.</p> + +<p>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 <em>not yet</em> +functioning in the form that is typical of the tissue in +question; and, strange to say, these “embryonic” cells—<span class="pagenum" title="183"><a name="Page_183" id="Page_183"></a></span><i>i.e.</i> +the “cambium” in higher plants and many kinds of +cells in animals—<em>can</em> 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.</p> + +<p><span class="pagenum" title="184"><a name="Page_184" id="Page_184"></a></span></p> + + +<h4 class="fs120">2. <span class="smcap">Physiological Adaptation</span><a name="FNanchor_89_89" id="FNanchor_89_89"></a><a href="#Footnote_89_89" class="fnanchor">89</a></h4> + +<p>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.</p> + +<p>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<span class="pagenum" title="185"><a name="Page_185" id="Page_185"></a></span> +are these “processes” <i lang="la" xml:lang="la">a priori</i> regarded as being physical +or chemical <em>themselves</em>: 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, <i>e.g.</i> owing to the production of +some insoluble compound, or whether we do not.</p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="186"><a name="Page_186" id="Page_186"></a></span></p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">SPECIFIC ADAPTEDNESS <em>NOT</em> “ADAPTATION”</span></p> + +<p>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.</p> + +<p>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 <em>is</em> no simple “membrane” in the +organism, but a complicated organisation of an almost<span class="pagenum" title="187"><a name="Page_187" id="Page_187"></a></span> +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 <span class="nowrap">nature.<a name="FNanchor_90_90" id="FNanchor_90_90"></a><a href="#Footnote_90_90" class="fnanchor">90</a></span></p> + +<p>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.</p> + +<p>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>i.e.</i> 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.</p> + +<p><span class="pagenum" title="188"><a name="Page_188" id="Page_188"></a></span></p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">PRIMARY AND SECONDARY ADAPTATIONS IN PHYSIOLOGY</span></p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="189"><a name="Page_189" id="Page_189"></a></span></p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">ON CERTAIN PRE-REQUISITES OF ADAPTATIONS IN GENERAL</span></p> + +<p>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 <i lang="la" xml:lang="la">a priori</i> 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?</p> + +<p>We know that the <em>state of functioning</em> must be altered +in order to call forth any sort of adaptation at all. Now, +there can be no doubt that <i lang="la" xml:lang="la">a priori</i> 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 <i lang="la" xml:lang="la">a priori</i> 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<span class="pagenum" title="190"><a name="Page_190" id="Page_190"></a></span> +poison has really acted in some way, and in this case we +shall indeed find regulations.</p> + +<p>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 <em>could</em> 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.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">ON CERTAIN GROUPS OF PRIMARY PHYSIOLOGICAL ADAPTATIONS</span></p> + +<p><i>General Remarks on Irritability.</i>—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<span class="pagenum" title="191"><a name="Page_191" id="Page_191"></a></span> +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 <i class="biological-name">Mimosa</i> 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 +<span class="nowrap">Weber.<a name="FNanchor_91_91" id="FNanchor_91_91"></a><a href="#Footnote_91_91" class="fnanchor">91</a></span></p> + +<p>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-<span class="pagenum" title="192"><a name="Page_192" id="Page_192"></a></span>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 <span class="nowrap">found.<a name="FNanchor_92_92" id="FNanchor_92_92"></a><a href="#Footnote_92_92" class="fnanchor">92</a></span></p> + +<p>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 <em>in</em> 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 <em>specific</em> character of functioning +in its different types, by proving that one of the <em>general</em> +features of <em>all</em> functioning may comparatively easily be<span class="pagenum" title="193"><a name="Page_193" id="Page_193"></a></span> +understood. It seems to me that this important logical +point has not always received the attention it deserved.</p> + +<p><i>The Regulation of Heat Production.</i><a name="FNanchor_93_93" id="FNanchor_93_93"></a><a href="#Footnote_93_93" class="fnanchor">93</a>—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.</p> + +<p>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<span class="pagenum" title="194"><a name="Page_194" id="Page_194"></a></span> +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 <span class="nowrap">consists.<a name="FNanchor_94_94" id="FNanchor_94_94"></a><a href="#Footnote_94_94" class="fnanchor">94</a></span></p> + +<p><i>Primary Regulations in the Transport of Materials and +Certain Phenomena of Osmotic Pressure.</i>—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<span class="pagenum" title="195"><a name="Page_195" id="Page_195"></a></span> +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.</p> + +<p>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 <span class="nowrap">Mayenburg<a name="FNanchor_95_95" id="FNanchor_95_95"></a><a href="#Footnote_95_95" class="fnanchor">95</a></span> has +found that sundry of the species of <i class="biological-name">Aspergillus</i>, the common +mould, are able to live in very highly concentrated solutions +of several salts (KNO<sub>3</sub> and Na<sub>2</sub>SO<sub>4</sub>). 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 <span class="nowrap">physiological<a name="FNanchor_96_96" id="FNanchor_96_96"></a><a href="#Footnote_96_96" class="fnanchor">96</a></span> regulation only;<span class="pagenum" title="196"><a name="Page_196" id="Page_196"></a></span> +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 +<span class="nowrap">possible.<a name="FNanchor_97_97" id="FNanchor_97_97"></a><a href="#Footnote_97_97" class="fnanchor">97</a></span></p> + +<p>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 +<span class="nowrap">Sumner<a name="FNanchor_98_98" id="FNanchor_98_98"></a><a href="#Footnote_98_98" class="fnanchor">98</a></span> would have to be taken into account by any one<span class="pagenum" title="197"><a name="Page_197" id="Page_197"></a></span> +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.</p> + +<p><i>Chromatic Regulations in Algae.</i>—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<sub>2</sub>) 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 <span class="nowrap">said<a name="FNanchor_99_99" id="FNanchor_99_99"></a><a href="#Footnote_99_99" class="fnanchor">99</a></span> 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 +<i class="biological-name">Oscillariae</i>, that <span class="nowrap">Gaidukow<a name="FNanchor_100_100" id="FNanchor_100_100"></a><a href="#Footnote_100_100" class="fnanchor">100</a></span> 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<span class="pagenum" title="198"><a name="Page_198" id="Page_198"></a></span> +<span class="nowrap">case.<a name="FNanchor_101_101" id="FNanchor_101_101"></a><a href="#Footnote_101_101" class="fnanchor">101</a></span> 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.”</p> + +<p><i>Metabolic Regulations.</i>—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 <span class="nowrap">view.<a name="FNanchor_102_102" id="FNanchor_102_102"></a><a href="#Footnote_102_102" class="fnanchor">102</a></span></p> +<p><span class="pagenum" title="199"><a name="Page_199" id="Page_199"></a></span></p> +<p>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 <span class="nowrap">fuel.<a name="FNanchor_103_103" id="FNanchor_103_103"></a><a href="#Footnote_103_103" class="fnanchor">103</a></span></p> + +<p>It is in the state of fasting, <i>i.e.</i> in the case of a real +absence of <em>all</em> 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<span class="pagenum" title="200"><a name="Page_200" id="Page_200"></a></span> +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. <span class="nowrap">Schultz<a name="FNanchor_104_104" id="FNanchor_104_104"></a><a href="#Footnote_104_104" class="fnanchor">104</a></span> 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 <span class="nowrap">powers.<a name="FNanchor_105_105" id="FNanchor_105_105"></a><a href="#Footnote_105_105" class="fnanchor">105</a></span></p> + +<p>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<span class="pagenum" title="201"><a name="Page_201" id="Page_201"></a></span> +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.</p> + +<p>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.</p> + +<p>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 <em>might</em> be some ferments equally able to destroy different +classes of <span class="nowrap">compounds,<a name="FNanchor_106_106" id="FNanchor_106_106"></a><a href="#Footnote_106_106" class="fnanchor">106</a></span> and that the most nutritive compound<span class="pagenum" title="202"><a name="Page_202" id="Page_202"></a></span> +is used up first <em>may</em> be a question of physico-chemical +equilibrium.</p> + +<p>That is almost <span class="nowrap">all<a name="FNanchor_107_107" id="FNanchor_107_107"></a><a href="#Footnote_107_107" class="fnanchor">107</a></span> 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 <em>inside</em> +the body interior, we meet, even in animals, regulations of a +far more developed type.</p> + +<p>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<span class="pagenum" title="203"><a name="Page_203" id="Page_203"></a></span> +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.</p> + +<p>Such a statement, of course, does not say that all +metabolism has proved to be of a chemical nature: the +<em>action</em> of the ferment when produced is chemical, but we +do not know at all <em>how</em> 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 <em>secretion</em> in the <em>first</em> 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<span class="pagenum" title="204"><a name="Page_204" id="Page_204"></a></span> +any secondary regulation with regard to the real <em>production</em> +of the ferment? I am sorry that I cannot answer this +question affirmatively. Nothing is <em>known</em> at present, even +here, that really proves the existence of adaptation of the +secondary type: there <em>might</em> be a sort of statical “harmony” +at the base of it all, established before all functioning <em>for</em> +<span class="nowrap">functioning.<a name="FNanchor_108_108" id="FNanchor_108_108"></a><a href="#Footnote_108_108" class="fnanchor">108</a></span></p> + +<p>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 <span class="nowrap">alone.<a name="FNanchor_109_109" id="FNanchor_109_109"></a><a href="#Footnote_109_109" class="fnanchor">109</a></span> +This is a new indicium of the primacy of <em>form</em> in the +organism.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">IMMUNITY THE ONLY TYPE OF A SECONDARY PHYSIOLOGICAL +ADAPTATION</span></p> + +<p>There is only one class of physiological processes in +which the type of the real secondary regulation occurs.<span class="pagenum" title="205"><a name="Page_205" id="Page_205"></a></span> +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 <em>immunity</em> 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.</p> + +<p>The adaptive faculty of the organism against inorganic +poisonous <span class="nowrap">substances<a name="FNanchor_110_110" id="FNanchor_110_110"></a><a href="#Footnote_110_110" class="fnanchor">110</a></span> 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<span class="pagenum" title="206"><a name="Page_206" id="Page_206"></a></span> +instantly fatal if administered at the first <span class="nowrap">dose.<a name="FNanchor_111_111" id="FNanchor_111_111"></a><a href="#Footnote_111_111" class="fnanchor">111</a></span> 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.</p> + +<p>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 <span class="nowrap">Metschnikoff<a name="FNanchor_112_112" id="FNanchor_112_112"></a><a href="#Footnote_112_112" class="fnanchor">112</a></span> +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 <span class="nowrap">ones.<a name="FNanchor_113_113" id="FNanchor_113_113"></a><a href="#Footnote_113_113" class="fnanchor">113</a></span> 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.</p> + +<p><span class="pagenum" title="207"><a name="Page_207" id="Page_207"></a></span></p> + +<p>It is impossible to say <span class="nowrap">here<a name="FNanchor_114_114" id="FNanchor_114_114"></a><a href="#Footnote_114_114" class="fnanchor">114</a></span> 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 <em>future</em>, 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 <em>more</em> 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 <span class="nowrap">feature.<a name="FNanchor_115_115" id="FNanchor_115_115"></a><a href="#Footnote_115_115" class="fnanchor">115</a></span></p> + +<p>This phenomenon in particular—the production of <em>more</em> +of the antitoxin or the “precipitin” than is actually<span class="pagenum" title="208"><a name="Page_208" id="Page_208"></a></span> +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 <span class="nowrap">Ehrlich,<a name="FNanchor_116_116" id="FNanchor_116_116"></a><a href="#Footnote_116_116" class="fnanchor">116</a></span> 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 <span class="nowrap">concept.<a name="FNanchor_117_117" id="FNanchor_117_117"></a><a href="#Footnote_117_117" class="fnanchor">117</a></span></p> + +<p>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<span class="pagenum" title="209"><a name="Page_209" id="Page_209"></a></span> +specificity in the production of antitoxins also. It is, of +course, the <em>fact</em> 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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">NO GENERAL POSITIVE RESULT FROM THIS CHAPTER</span></p> + +<p>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.</p> + +<p>We freely admit we have not gained any really new +<em>proof</em>, 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.</p> + +<p>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 <em>more</em> of +the protecting substance than is actually necessary could +hardly be said to be “chemical.”</p> + +<p>In fact, we are well entitled to say that we have reached +here the very heart of life and of biology. If nevertheless<span class="pagenum" title="210"><a name="Page_210" id="Page_210"></a></span> +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 <em>might</em> 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 <em>absurdity</em>, 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 +<em>proof</em> must reduce to <em>absurdity</em> all the possibilities except +one, in order to be a proof.</p> + +<p>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 <span class="nowrap">say<a name="FNanchor_118_118" id="FNanchor_118_118"></a><a href="#Footnote_118_118" class="fnanchor">118</a></span> 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.</p> + +<p>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<span class="pagenum" title="211"><a name="Page_211" id="Page_211"></a></span> +personally should not hesitate to say so. But that is not +the question. We have to ask: Is any new proof, <em>independent +of every other</em>, 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 <em>simple</em> +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.</p> + +<p>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 +<i lang="la" xml:lang="la">ad absurdum</i> 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.</p> + +<p>With this chapter we conclude the study of organic +regulation in all its forms, as far as morphogenesis and +metabolism are in question.</p> + +<p>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.</p> + +<p><span class="pagenum" title="212"><a name="Page_212" id="Page_212"></a></span></p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">A FEW REMARKS ON THE LIMITS OF REGULABILITY</span></p> + +<p>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 <span class="nowrap">time;<a name="FNanchor_119_119" id="FNanchor_119_119"></a><a href="#Footnote_119_119" class="fnanchor">119</a></span> everything is either +complete, whenever it occurs, or it does not occur at all.</p> + +<p>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<span class="pagenum" title="213"><a name="Page_213" id="Page_213"></a></span> +any missing part; but at present we know absolutely +nothing about such <span class="nowrap">conditions.<a name="FNanchor_120_120" id="FNanchor_120_120"></a><a href="#Footnote_120_120" class="fnanchor">120</a></span></p> + +<p>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.</p> + +<hr class="short" /> + +<p><span class="pagenum" title="214"><a name="Page_214" id="Page_214"></a></span></p> + + + + +<h3><i>D.</i> INHERITANCE: SECOND PROOF OF THE AUTONOMY OF LIFE</h3> + + +<p>All organisms are endowed with the faculty of re-creating +their own initial form of existence.</p> + +<p>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, <i lang="la" xml:lang="la">ceteris paribus</i>, it will behave again as +it did when last it existed.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="smcap">The Material Continuity in Inheritance</span></p> + +<p>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<span class="pagenum" title="215"><a name="Page_215" id="Page_215"></a></span> +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.</p> + +<p>The important problem now presents itself: What is the<span class="pagenum" title="216"><a name="Page_216" id="Page_216"></a></span> +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 +<i lang="la" xml:lang="la">a priori</i> 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.</p> + + +<p class="tac pt12b02em"><span class="smcap">On Certain Theories which Seek to Compare +Inheritance to Memory</span></p> + +<p>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.</p> + +<p>It is not clear, either from Hering’s <span class="nowrap">paper<a name="FNanchor_121_121" id="FNanchor_121_121"></a><a href="#Footnote_121_121" class="fnanchor">121</a></span> or from +Semon’s <span class="nowrap">book,<a name="FNanchor_122_122" id="FNanchor_122_122"></a><a href="#Footnote_122_122" class="fnanchor">122</a></span> 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 autho<span class="pagenum" title="217"><a name="Page_217" id="Page_217"></a></span>r’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 <em>most</em> important +point about the matter in question must remain <i lang="la" xml:lang="la">in dubio</i>.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="218"><a name="Page_218" id="Page_218"></a></span> +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.</p> + +<p>But such an assumption most certainly cannot be true.</p> + +<p>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 <em>primary perfection</em>, 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 <em>contingency</em> of both of them.</p> + +<p>The word “memory,” therefore, may be applied to the<span class="pagenum" title="219"><a name="Page_219" id="Page_219"></a></span> +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 <em>know</em> +that there <em>is</em> 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.”</p> + + +<p class="tac pt12b02em"><span class="smcap">The Complex-Equipotential System and its Rôle in +Inheritance</span><a name="FNanchor_123_123" id="FNanchor_123_123"></a><a href="#Footnote_123_123" class="fnanchor">123</a></p> + +<p>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.</p> + +<p>Let the discussions that are to follow be placed upon +a basis as broad as possible.</p> + +<p>Our studies of morphogenetic restitution have shown us +that besides the harmonious-equipotential systems another +and widely different type of morphogenetic “systems” (<i>i.e.</i><span class="pagenum" title="220"><a name="Page_220" id="Page_220"></a></span> +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.</p> + +<p>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 <span class="pagenum" title="221"><a name="Page_221" id="Page_221"></a></span>“ideal +whole,” though this ideal whole will never be realised in +its proper <span class="nowrap">wholeness.<a name="FNanchor_124_124" id="FNanchor_124_124"></a><a href="#Footnote_124_124" class="fnanchor">124</a></span></p> + +<p>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 +<span class="nowrap">cell<a name="FNanchor_125_125" id="FNanchor_125_125"></a><a href="#Footnote_125_125" class="fnanchor">125</a></span> 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.</p> + +<p>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 <span class="nowrap">proper,<a name="FNanchor_126_126" id="FNanchor_126_126"></a><a href="#Footnote_126_126" class="fnanchor">126</a></span> 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<span class="pagenum" title="222"><a name="Page_222" id="Page_222"></a></span> +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 <span class="nowrap">lead,<a name="FNanchor_127_127" id="FNanchor_127_127"></a><a href="#Footnote_127_127" class="fnanchor">127</a></span> 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.</p> + +<p>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 <i class="biological-name">Clavellina</i>, 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<span class="pagenum" title="223"><a name="Page_223" id="Page_223"></a></span> +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.</p> + +<p>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<span class="pagenum" title="224"><a name="Page_224" id="Page_224"></a></span> +morphogenetic course—the production of the whole +individual.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="smcap">The Second Proof of Life-Autonomy. Entelechy at +the Bottom of Inheritance</span></p> + +<p>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 <em>genesis</em> of our complex systems that show equipotentiality.</p> + +<p>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<span class="pagenum" title="225"><a name="Page_225" id="Page_225"></a></span> +then, or from another point of view at the beginning, +a single cellular element represents the very primordial +egg-cell.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>But could such a theory—irrespective of all the experimental +facts which contradict it—could such a theory +stand before the <em>one</em> fact, that there occurs a <em>genesis</em> 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,<span class="pagenum" title="226"><a name="Page_226" id="Page_226"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>Let us again apply the name entelechy to that which +lies at the very beginning of all individual morphogenesis.</p> + +<p>Entelechy thus proves to be also that which may be +said to lie at the very root of <span class="nowrap">inheritance,<a name="FNanchor_128_128" id="FNanchor_128_128"></a><a href="#Footnote_128_128" class="fnanchor">128</a></span> or at least of<span class="pagenum" title="227"><a name="Page_227" id="Page_227"></a></span> +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 <i lang="la" xml:lang="la">per se</i>.</p> + + +<p class="tac pt12b02em"><span class="smcap">The Significance of the Material Continuity in +Inheritance</span></p> + +<p>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.</p> + +<p>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<span class="pagenum" title="228"><a name="Page_228" id="Page_228"></a></span> +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 <em>order</em>, +in the one generation and in the next. But may not the +material continuity which exists in inheritance account +perhaps for the material elements <em>which are to be ordered</em>? +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?</p> + + +<p class="tac pt12b02em"><span class="smcap">The Experimental Facts about Inheritance</span></p> + +<p>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 <em>had</em> been<span class="pagenum" title="229"><a name="Page_229" id="Page_229"></a></span> +discovered already, stated with the utmost clearness and +precision by the Augustinian monk, Gregor <span class="nowrap">Mendel,<a name="FNanchor_129_129" id="FNanchor_129_129"></a><a href="#Footnote_129_129" class="fnanchor">129</a></span> as +early as 1865, though it had been completely forgotten +ever since.</p> + +<p>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 <span class="nowrap">mixed<a name="FNanchor_130_130" id="FNanchor_130_130"></a><a href="#Footnote_130_130" class="fnanchor">130</a></span> 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.</p> + +<p>Before discussing what may follow from Mendel’s +discovery for the theory of heredity, we must lay stress<span class="pagenum" title="230"><a name="Page_230" id="Page_230"></a></span> +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.</p> + +<p>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 <span class="nowrap">themselves.<a name="FNanchor_131_131" id="FNanchor_131_131"></a><a href="#Footnote_131_131" class="fnanchor">131</a></span></p> + +<p>We have not yet considered one feature of all experi<span class="pagenum" title="231"><a name="Page_231" id="Page_231"></a></span>ments +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.</p> + +<p>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.”</p> + +<p>Besides the researches relating to the rule of Mendel<span class="pagenum" title="232"><a name="Page_232" id="Page_232"></a></span> +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.</p> + +<p>Starting from the discovery of Vernon, that the hybrids +of sea-urchins are of different types according to the +season, <span class="nowrap">Herbst<a name="FNanchor_132_132" id="FNanchor_132_132"></a><a href="#Footnote_132_132" class="fnanchor">132</a></span> 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 <i class="biological-name">Sphaerechinus</i> to enter into +the <span class="nowrap">first<a name="FNanchor_133_133" id="FNanchor_133_133"></a><a href="#Footnote_133_133" class="fnanchor">133</a></span> phase of artificial parthenogenesis and then fertilised +them with the sperm of <i class="biological-name">Echinus</i>, 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.</p> + +<p>What is shown, in the first place, by these discoveries<span class="pagenum" title="233"><a name="Page_233" id="Page_233"></a></span> +is the importance of an arranging and ruling factor in spite +of all units. The organism is always one <em>whole</em> whether the +paternal properties prevail or the more complicated maternal +ones; in other words, all so-called properties that consist in the +<em>spatial relations of parts</em> 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.</p> + + +<p class="tac pt12b02em"><span class="smcap">The Rôle of the Nucleus in Inheritance</span></p> + +<p>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.</p> + +<p><span class="pagenum" title="234"><a name="Page_234" id="Page_234"></a></span></p> + +<p>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 <span class="nowrap">nuclei,<a name="FNanchor_134_134" id="FNanchor_134_134"></a><a href="#Footnote_134_134" class="fnanchor">134</a></span> deals “especially” with the +protoplasmic nature of its “systems.”</p> + +<p>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?</p> + +<p>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<span class="pagenum" title="235"><a name="Page_235" id="Page_235"></a></span> +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.</p> + +<p>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 <span class="nowrap">Boveri<a name="FNanchor_135_135" id="FNanchor_135_135"></a><a href="#Footnote_135_135" class="fnanchor">135</a></span> 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<span class="pagenum" title="236"><a name="Page_236" id="Page_236"></a></span> +pure maternal type. This experiment seems to place the +morphogenetic importance of protoplasm beyond all doubt.</p> + +<p>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 <span class="nowrap">belief.<a name="FNanchor_136_136" id="FNanchor_136_136"></a><a href="#Footnote_136_136" class="fnanchor">136</a></span></p> + +<p>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.</p> + +<p>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 <span class="nowrap">present.<a name="FNanchor_137_137" id="FNanchor_137_137"></a><a href="#Footnote_137_137" class="fnanchor">137</a></span></p> +<p><span class="pagenum" title="237"><a name="Page_237" id="Page_237"></a></span></p> + +<p class="tac pt12b02em"><span class="smcap">Variation and Mutation</span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="238"><a name="Page_238" id="Page_238"></a></span> +variation has been most carefully studied by statistical +methods, Galton and Weldon being the well-known +pioneers in this <span class="nowrap">field.<a name="FNanchor_138_138" id="FNanchor_138_138"></a><a href="#Footnote_138_138" class="fnanchor">138</a></span> 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 <span class="nowrap">biologists<a name="FNanchor_139_139" id="FNanchor_139_139"></a><a href="#Footnote_139_139" class="fnanchor">139</a></span> 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.</p> + +<p>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 <span class="nowrap">exceptions<a name="FNanchor_140_140" id="FNanchor_140_140"></a><a href="#Footnote_140_140" class="fnanchor">140</a></span> +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<span class="pagenum" title="239"><a name="Page_239" id="Page_239"></a></span> +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 +<span class="nowrap">meaning.<a name="FNanchor_141_141" id="FNanchor_141_141"></a><a href="#Footnote_141_141" class="fnanchor">141</a></span></p> + +<hr class="short" /> + +<p><span class="pagenum" title="240"><a name="Page_240" id="Page_240"></a></span></p> + + +<h3><span class="smcap">Conclusions from the First Main Part of these +Lectures</span></h3> + + +<p>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 <em>individual</em>, 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.</p> + +<p>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<span class="pagenum" title="241"><a name="Page_241" id="Page_241"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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,<span class="pagenum" title="242"><a name="Page_242" id="Page_242"></a></span> +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 +<em>does</em> 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.</p> + +<hr class="chap" /> + +<p><span class="pagenum" title="243"><a name="Page_243" id="Page_243"></a></span></p> + + + + +<h2>PART II</h2> + +<h2>SYSTEMATICS AND HISTORY</h2> + +<h3><i>A.</i> THE PRINCIPLES OF SYSTEMATICS</h3> + + +<p class="tac pt12b02em"><span class="smcap">Rational Systematics</span></p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="244"><a name="Page_244" id="Page_244"></a></span></p> + +<p>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<sub>n</sub>H<sub>2n+1</sub>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 <i>n</i> 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.</p> + +<p>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<span class="pagenum" title="245"><a name="Page_245" id="Page_245"></a></span> +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.</p> + +<p>We are dealing here with some of the most remarkable +properties of the so-called synthetic judgments <i lang="la" xml:lang="la">a priori</i> 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.</p> + +<p>All other genera and species, whether of natural bodies +or of facts, can be related only on the basis of empirical +abstraction, <i>i.e.</i> 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<span class="pagenum" title="246"><a name="Page_246" id="Page_246"></a></span> +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.</p> + + +<p class="tac pt12b02em"><span class="smcap">Biological Systematics</span></p> + +<p>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.</p> + +<p>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<span class="pagenum" title="247"><a name="Page_247" id="Page_247"></a></span> +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.</p> + +<p>But, nevertheless, we do not understand the <i lang="fr" xml:lang="fr">raison +d’être</i> 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.</p> + +<p>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 <i lang="la" xml:lang="la">a priori</i> 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.</p> + +<p>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<span class="pagenum" title="248"><a name="Page_248" id="Page_248"></a></span> +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.</p> + +<p>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 <span class="nowrap">possible.<a name="FNanchor_142_142" id="FNanchor_142_142"></a><a href="#Footnote_142_142" class="fnanchor">142</a></span></p> + +<p>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.</p> + +<p>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.<span class="pagenum" title="249"><a name="Page_249" id="Page_249"></a></span> +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.</p> + +<hr class="short" /> + +<p><span class="pagenum" title="250"><a name="Page_250" id="Page_250"></a></span></p> + + + + +<h3><i>B.</i> THE THEORY OF DESCENT</h3> + + +<h4 class="fs120">1. <span class="smcap">Generalities</span></h4> + +<p>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.</p> + +<p>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<span class="pagenum" title="251"><a name="Page_251" id="Page_251"></a></span> +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.</p> + +<p>The theory of descent is the hypothetic statement that +the organisms are really allied by blood among each other, +in spite of their <span class="nowrap">diversities.<a name="FNanchor_143_143" id="FNanchor_143_143"></a><a href="#Footnote_143_143" class="fnanchor">143</a></span> The question about their +so-called monophyletic or polyphyletic origin is of secondary +importance compared with the statement of relationship in +general.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="252"><a name="Page_252" id="Page_252"></a></span> +are to be mentioned in the first place. If, indeed, on each +of the different islands, <i>A</i> <i>B</i> <i>C</i> and <i>D</i>, 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.</p> + +<p>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 +<i lang="la" xml:lang="la">ad hoc</i>; 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 <i lang="la" xml:lang="la">causa vera</i>.</p> + +<p><span class="pagenum" title="253"><a name="Page_253" id="Page_253"></a></span></p> + +<p>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 <em>similarities and diversities by gradation</em>; 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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE COVERT PRESUMPTION OF ALL THEORIES OF DESCENT</span></p> + +<p>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<span class="pagenum" title="254"><a name="Page_254" id="Page_254"></a></span> +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 <em>any</em> 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 <i>A</i> to become the specific form <i>B</i>, have been +such as only to change <em>in part</em> that original form <i>A</i>. +That is to say: the similarities between <i>A</i> and <i>B</i> must +never have become overshadowed by their diversities.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="255"><a name="Page_255" id="Page_255"></a></span> +the diversities. The <em>similarities</em> now are “explained”; +that is to say, they are understood as resting on but one +principle: the similarities are understood as being due to +<span class="nowrap">inheritance;<a name="FNanchor_144_144" id="FNanchor_144_144"></a><a href="#Footnote_144_144" class="fnanchor">144</a></span> 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.</p> + +<p>Understanding then what is explained by the theory +of descent with its necessary appendix, we also understand +at once what is <em>not</em> 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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE SMALL VALUE OF PURE PHYLOGENY</span></p> + +<p>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<span class="pagenum" title="256"><a name="Page_256" id="Page_256"></a></span> +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.</p> + +<p>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?</p> + +<p>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<span class="pagenum" title="257"><a name="Page_257" id="Page_257"></a></span> +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 <i class="biological-name">Sagitta</i> type of worms; fourthly, +from spiders; fifthly, from <i class="biological-name">Limulus</i>, 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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">HISTORY AND SYSTEMATICS</span></p> + +<p>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<span class="pagenum" title="258"><a name="Page_258" id="Page_258"></a></span> +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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="259"><a name="Page_259" id="Page_259"></a></span> +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.</p> + +<p><span class="pagenum" title="260"><a name="Page_260" id="Page_260"></a></span></p> + + +<h4 class="fs120">2. <span class="smcap">The Principles of Darwinism</span></h4> + +<p>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<span class="pagenum" title="261"><a name="Page_261" id="Page_261"></a></span> +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.</p> + +<p>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!</p> + +<p>It is to Darwinism of the <em>dogmatic</em> 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 <i lang="la" xml:lang="la">a priori</i> 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.</p> + +<p>The logical structure of dogmatic Darwinism reveals +two different parts, which have nothing at all to do with +one another.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">NATURAL SELECTION</span></p> + +<p>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<span class="pagenum" title="262"><a name="Page_262" id="Page_262"></a></span> +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.</p> + +<p>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 <i lang="la" xml:lang="la">a priori</i>, do <em>not</em> 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?</p> + +<p>In denying any real explanatory value to the concept<span class="pagenum" title="263"><a name="Page_263" id="Page_263"></a></span> +of natural selection I am far from denying the action of +natural selection. On the contrary, natural selection, to +some degree, is <em>self-evident</em>; 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, <i>e.g.</i> special houses or special streets, as +by the degree of immunity. But, certainly, natural selection +is a <i lang="la" xml:lang="la">causa vera</i> in many other cases.</p> + +<p>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<span class="pagenum" title="264"><a name="Page_264" id="Page_264"></a></span> +for the non-existence of what is not, with the sufficient +reason of what is.</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">FLUCTUATING VARIATION THE ALLEGED CAUSE OF ORGANIC +DIVERSITY</span></p> + +<p>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.</p> + +<p>It could hardly be said to be beyond the realm of +possibility that such differences among organic species as<span class="pagenum" title="265"><a name="Page_265" id="Page_265"></a></span> +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 <i>n</i> and let the value +<i>n</i> + <i>m</i>—<i>m</i> being variable—which is represented in fewer +individuals of course than is <i>n</i>, be such as to offer +advantages in the struggle for existence; then the +individuals marked by <i>n</i> + <i>m</i> 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, <i>n</i> + <i>m</i> in any of its variable +forms must be able to become the average value of the +second generation, as <i>n</i> was the average value of the first. +Out of the second generation again it would be the few +individuals marked by <i>n</i> + <i>m</i> + <i>o</i>, which would be selected; +<i>n</i> + <i>m</i> + <i>o</i> would be the new average; afterwards <i>n</i> + <i>m</i> + <i>o</i> + <i>p</i> +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.</p> + +<p>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<span class="pagenum" title="266"><a name="Page_266" id="Page_266"></a></span> +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.</p> + +<p>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.</p> + +<p>I cannot enter here into the whole subject of Darwinian +<span class="nowrap">criticism.<a name="FNanchor_145_145" id="FNanchor_145_145"></a><a href="#Footnote_145_145" class="fnanchor">145</a></span> 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, <i>e.g.</i> 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?</p> +<p><span class="pagenum" title="267"><a name="Page_267" id="Page_267"></a></span></p> +<p>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.</p> + +<p>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 <i lang="la" xml:lang="la">experimentum crucis</i> of Darwinism.</p> + +<p>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 <i class="biological-name">Triton taeniatus</i>, 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 inevit<span class="pagenum" title="268"><a name="Page_268" id="Page_268"></a></span>able +to assume that <em>all</em> the ancestors of our <i class="biological-name">Triton</i> 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 +<em>neither</em> they themselves <em>nor</em> 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.</p> + +<p>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 <em>all</em> sea-urchins +are capable of the ontogenetical restitution in +question, <em>all</em> of their ancestors therefore must have acquired +it, and they could do that only <em>if</em> they became halved at +first by some accident during early embryology. But we +shall not insist any further on this instance, for it would<span class="pagenum" title="269"><a name="Page_269" id="Page_269"></a></span> +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.</p> + +<p>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 <em>Species</em>,” that is of organic <em>diversities</em>, 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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">DARWINISM FAILS ALL ALONG THE LINE</span></p> + +<p>The result of our discussion then must be this: selection +has proved to be a negative factor only, and fluctuating<span class="pagenum" title="270"><a name="Page_270" id="Page_270"></a></span> +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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="271"><a name="Page_271" id="Page_271"></a></span></p> + + +<h4 class="fs120">3. <span class="smcap">The Principles of Lamarckism.</span></h4> + +<p>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.</p> + +<p><span class="pagenum" title="272"><a name="Page_272" id="Page_272"></a></span></p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">ADAPTATION AS THE STARTING-POINT</span></p> + +<p>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 <em>any</em> 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 <i lang="la" xml:lang="la">causa vera</i>.</p> + +<p>It is important to notice that this <i lang="la" xml:lang="la">causa vera</i> 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<span class="pagenum" title="273"><a name="Page_273" id="Page_273"></a></span> +most clearly seen what the logical assumptions of pure +Lamarckism are. Next to Cope, August <span class="nowrap">Pauly<a name="FNanchor_146_146" id="FNanchor_146_146"></a><a href="#Footnote_146_146" class="fnanchor">146</a></span> 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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE ACTIVE STORING OF CONTINGENT VARIATIONS AS A +HYPOTHETIC PRINCIPLE</span></p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="274"><a name="Page_274" id="Page_274"></a></span></p> + +<p>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 <em>judgment</em> is the fourth foundation of the act of +volition.</p> + +<p>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<span class="pagenum" title="275"><a name="Page_275" id="Page_275"></a></span> +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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">CRITICISM OF THE “INHERITANCE OF ACQUIRED CHARACTERS” +ASSUMED BY LAMARCKISM</span></p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="276"><a name="Page_276" id="Page_276"></a></span></p> + +<p>The name of “acquired characters” may <i lang="la" xml:lang="la">a priori</i> 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.</p> + +<p>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 <span class="nowrap">congenital.<a name="FNanchor_147_147" id="FNanchor_147_147"></a><a href="#Footnote_147_147" class="fnanchor">147</a></span> 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 <span class="nowrap">altogether.<a name="FNanchor_148_148" id="FNanchor_148_148"></a><a href="#Footnote_148_148" class="fnanchor">148</a></span> 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 <span class="nowrap">know,<a name="FNanchor_149_149" id="FNanchor_149_149"></a><a href="#Footnote_149_149" class="fnanchor">149</a></span> 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<span class="pagenum" title="277"><a name="Page_277" id="Page_277"></a></span> +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.</p> + +<p>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 +<span class="nowrap">groups?<a name="FNanchor_150_150" id="FNanchor_150_150"></a><a href="#Footnote_150_150" class="fnanchor">150</a></span> 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.</p> +<p><span class="pagenum" title="278"><a name="Page_278" id="Page_278"></a></span></p> +<p>But are there any facts?</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="279"><a name="Page_279" id="Page_279"></a></span> +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 +<span class="nowrap">itself.<a name="FNanchor_151_151" id="FNanchor_151_151"></a><a href="#Footnote_151_151" class="fnanchor">151</a></span> 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, <i class="biological-name">Adiantum</i>, is known to +assume a very typical modification of form and structure, if +grown on serpentine; now <span class="nowrap">Sadebeck,<a name="FNanchor_152_152" id="FNanchor_152_152"></a><a href="#Footnote_152_152" class="fnanchor">152</a></span> while cultivating this +serpentine modification of <i class="biological-name">Adiantum</i> 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<span class="pagenum" title="280"><a name="Page_280" id="Page_280"></a></span> +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 <em>several</em> 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 <em>sudden</em> change of the adaptive character, +corresponding to the actual conditions, sets in; but it is +enough that they do exist.</p> + +<p>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 +<span class="nowrap">inherited.<a name="FNanchor_153_153" id="FNanchor_153_153"></a><a href="#Footnote_153_153" class="fnanchor">153</a></span></p> +<p><span class="pagenum" title="281"><a name="Page_281" id="Page_281"></a></span></p> +<p>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 <i lang="la" xml:lang="la">causa vera</i>, yet certainly more +than a mere fiction.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">OTHER PRINCIPLES WANTED</span></p> + +<p>We have only dealt with the probability of the +inheritance of morphological or <span class="nowrap">physiological<a name="FNanchor_154_154" id="FNanchor_154_154"></a><a href="#Footnote_154_154" class="fnanchor">154</a></span> 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 <em>this</em> 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<span class="pagenum" title="282"><a name="Page_282" id="Page_282"></a></span> +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 <span class="nowrap">word.<a name="FNanchor_155_155" id="FNanchor_155_155"></a><a href="#Footnote_155_155" class="fnanchor">155</a></span></p> + +<p>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?</p> + +<p>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.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">CRITICISM OF THE HYPOTHESIS OF STORING AND HANDING +DOWN CONTINGENT VARIATIONS</span></p> + +<p>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.</p> + +<p>As it is important to understand well the real logical +nature of our objections to both of the great transformistic<span class="pagenum" title="283"><a name="Page_283" id="Page_283"></a></span> +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.</p> + +<p>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 <em>Species</em>.” 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<span class="pagenum" title="284"><a name="Page_284" id="Page_284"></a></span> +Darwinian dogmatists, while Lamarckism is antimaterialistic +by its very nature.</p> + +<p>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.</p> + +<p>The <em>contingency</em> 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<span class="pagenum" title="285"><a name="Page_285" id="Page_285"></a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>As far as the inheritance of truly adaptive characters +comes into account—that is, the inheritance of characters<span class="pagenum" title="286"><a name="Page_286" id="Page_286"></a></span> +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 <em>specific +organisation proper</em> is due to <em>contingent</em> 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.</p> + +<p>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 <em>exists</em> a faculty of a certain higher degree in the +organism, and this faculty cannot possibly have originated +by the process which <span class="nowrap">Lamarckians<a name="FNanchor_156_156" id="FNanchor_156_156"></a><a href="#Footnote_156_156" class="fnanchor">156</a></span> assume. But if their +principle fails in one instance, it fails as a <em>general</em> theory +altogether. And now, on the other hand, as we actually<span class="pagenum" title="287"><a name="Page_287" id="Page_287"></a></span> +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.</p> + +<p>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<span class="pagenum" title="288"><a name="Page_288" id="Page_288"></a></span> +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.</p> + +<p>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 <em>their</em> +structures.</p> + +<p>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 <span class="nowrap">form.<a name="FNanchor_157_157" id="FNanchor_157_157"></a><a href="#Footnote_157_157" class="fnanchor">157</a></span></p> + +<p>There is finally one group of facts often brought forward<span class="pagenum" title="289"><a name="Page_289" id="Page_289"></a></span> +against Lamarckism by Darwinian <span class="nowrap">authors<a name="FNanchor_158_158" id="FNanchor_158_158"></a><a href="#Footnote_158_158" class="fnanchor">158</a></span> which may be +called the logical <i lang="la" xml:lang="la">experimentum crucis</i> of this doctrine, an +<i lang="la" xml:lang="la">experimentum</i> 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.</p> + +<p>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.</p> + +<p><span class="pagenum" title="290"><a name="Page_290" id="Page_290"></a></span></p> + + +<h4 class="fs120">4. <span class="smcap">The Real Results and the Unsolved Problems of +Transformism</span></h4> + +<p>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.</p> + +<p>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<span class="pagenum" title="291"><a name="Page_291" id="Page_291"></a></span> +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.</p> + +<p>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 <span class="nowrap">possibility<a name="FNanchor_159_159" id="FNanchor_159_159"></a><a href="#Footnote_159_159" class="fnanchor">159</a></span> of +a discontinuous variation, that is of “mutation,” following +certain lines of tectonics and leading to <em>constant</em> 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.</p> + +<p>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<span class="pagenum" title="292"><a name="Page_292" id="Page_292"></a></span> +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.</p> + +<p>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.</p> + +<p>As we ourselves feel absolutely incapable of adding +anything specific to the general statement that there <em>must</em> +be an unknown principle of transformism, if the hypothesis +of descent is justified at all, we may here close our discussion +of the subject.</p> + +<p><span class="pagenum" title="293"><a name="Page_293" id="Page_293"></a></span></p> + + +<h4 class="fs120">5. <span class="smcap">The Logical Value of the Organic Form According to the<br />Different Transformistic Theories</span></h4> + +<p>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.</p> + +<p>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 <i lang="la" xml:lang="la">forma accidentalis</i> 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 <em>law</em> relating to this indefinite number: among<span class="pagenum" title="294"><a name="Page_294" id="Page_294"></a></span> +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?</p> + +<p>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.</p> + +<p>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.</p> + +<p>There is no <i lang="la" xml:lang="la">forma accidentalis</i>. Does that mean that +the <i lang="la" xml:lang="la">forma essentialis</i> is introduced by this mere statement? +And what would <em>that</em> assert about the character of +systematics?</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE ORGANIC FORM AND ENTELECHY</span></p> + +<p>This problem is not as simple as it might seem to be +at the first glance, and, in fact, it is insoluble at present.<span class="pagenum" title="295"><a name="Page_295" id="Page_295"></a></span> +It is here that the relation of the hypothetic transformistic +principle to our concept of entelechy is concerned.</p> + +<p>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?</p> + +<p>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 <em>harmony</em> 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 <i lang="la" xml:lang="la">formae essentiales</i>, +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:<span class="pagenum" title="296"><a name="Page_296" id="Page_296"></a></span> +there might one day be found a principle to account +for the totality of <span class="nowrap">possible<a name="FNanchor_160_160" id="FNanchor_160_160"></a><a href="#Footnote_160_160" class="fnanchor">160</a></span> forms, a principle based upon +the analysis of <span class="nowrap">entelechy.<a name="FNanchor_161_161" id="FNanchor_161_161"></a><a href="#Footnote_161_161" class="fnanchor">161</a></span> 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.</p> + +<hr class="short" /> + +<p><span class="pagenum" title="297"><a name="Page_297" id="Page_297"></a></span></p> + + +<h3><i>C.</i> THE LOGIC OF HISTORY</h3> + + +<p>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.</p> + +<p>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.</p> + +<p>But this, remember, was the utmost we were able to say +for phylogeny. It remains fantastic and for the most part<span class="pagenum" title="298"><a name="Page_298" id="Page_298"></a></span> +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.</p> + +<p>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.</p> + +<p>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 <i lang="la" xml:lang="la">a +priori</i>, if the word history is to signify more than a mere +enumeration?</p> + +<p><span class="pagenum" title="299"><a name="Page_299" id="Page_299"></a></span></p> + + +<h4 class="fs120">1. <span class="smcap">The Possible Aspects of History</span></h4> + +<p>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 <em>bodies</em> 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.</p> + +<p>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<span class="pagenum" title="300"><a name="Page_300" id="Page_300"></a></span> +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.</p> + +<p>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.</p> + +<p>In the first place, history may start as a mere enumeration +at the beginning, and at the end, in spite of all further<span class="pagenum" title="301"><a name="Page_301" id="Page_301"></a></span> +endeavour, may <em>remain</em> 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 <em>possible</em>.</p> + +<p>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 <em>evolution</em>, an evolving +of something; the word “evolution” being understood here +in a much wider sense than on former <span class="nowrap">occasions,<a name="FNanchor_162_162" id="FNanchor_162_162"></a><a href="#Footnote_162_162" class="fnanchor">162</a></span> and <em>including</em>, +for instance, the embryological alternative “evolutio” +or “epigenesis.”</p> + +<p>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 <em>has been</em> always +becomes the foundation of what <em>will be</em> in the <em>next</em> phase of +the historical process. There is a sort of <em>cumulation</em> of consecutive +phases, the later ones being impossible without the<span class="pagenum" title="302"><a name="Page_302" id="Page_302"></a></span> +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.</p> + +<p>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<span class="pagenum" title="303"><a name="Page_303" id="Page_303"></a></span> +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.</p> + +<p><span class="pagenum" title="304"><a name="Page_304" id="Page_304"></a></span></p> + + +<h4 class="fs120">2. <span class="smcap">Phylogenetic Possibilities</span></h4> + +<p>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 <em>always</em> 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 <em>not</em> 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.</p> + +<p>Darwinism and Lamarckism, regarding organic forms as +contingent, must at the same time regard organic history +as a cumulation; they indeed <em>might</em> 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.</p> + +<p>But any transformistic theory, which locates the very<span class="pagenum" title="305"><a name="Page_305" id="Page_305"></a></span> +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 <em>might</em> be evolution, and in fact I cannot admit +more than this <i lang="la" xml:lang="la">a priori</i>, 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 <i lang="la" xml:lang="la">ad infinitum</i>.<a name="FNanchor_163_163" id="FNanchor_163_163"></a><a href="#Footnote_163_163" class="fnanchor">163</a> 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 <span class="nowrap">without.<a name="FNanchor_164_164" id="FNanchor_164_164"></a><a href="#Footnote_164_164" class="fnanchor">164</a></span></p> + +<p>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.</p> + +<p><span class="pagenum" title="306"><a name="Page_306" id="Page_306"></a></span></p> + + +<h4 class="fs120">3. <span class="smcap">The History of Mankind</span></h4> + +<p>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 <em>mere fact</em> 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, +<em>has happened</em>, and where we also know at least some of the +factors concerned in it.</p> + +<p>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 <em>are</em> historical facts: +let us try to find out what these facts can teach us about +their succession.</p> + +<p>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<span class="pagenum" title="307"><a name="Page_307" id="Page_307"></a></span> +philosophical view of the universe. We shall try to treat +our subject as impartially as possible.</p> + +<p>Hegel says, in the introduction to his <cite lang="de" xml:lang="de">Phänomenologie +des Geistes</cite>: “<cite lang="de" xml:lang="de">Die Philosophie muss sich hüten erbaulich +sein zu wollen</cite>” (“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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="308"><a name="Page_308" id="Page_308"></a></span> +takes, and which I myself take in history in spite of this +unsatisfactory state of things?</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">CUMULATIONS IN HUMAN HISTORY</span></p> + +<p>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 <em>cumulations</em>, 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<span class="pagenum" title="309"><a name="Page_309" id="Page_309"></a></span> +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.</p> + +<p>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 <em>element</em> +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, +<i lang="la" xml:lang="la">qua</i> individual, which is concerned in <em>every</em> kind of history.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="310"><a name="Page_310" id="Page_310"></a></span> +form of rules, but these rules are <em>known</em> 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.</p> + +<p>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.</p> + +<p>If the mere <i lang="la" xml:lang="la">rerum cognoscere causas</i> 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 <i lang="de" xml:lang="de">den +ruhenden Pol in der Erscheinungen Flucht</i>.</p> + +<p><span class="pagenum" title="311"><a name="Page_311" id="Page_311"></a></span></p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">HUMAN HISTORY NOT AN “EVOLUTION”</span></p> + +<p>Quite another view of history has been maintained by +Hegel, if his explanations about the <i lang="de" xml:lang="de">Entwicklung des +objectiven Geistes</i> (“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 <em>evolution</em> 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?</p> + +<p>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<span class="pagenum" title="312"><a name="Page_312" id="Page_312"></a></span> +here simply what we meet everywhere in history—a sort +of cumulation resting upon a psychological basis.</p> + +<p>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 <em>human</em> mind. In the history of those +sciences which are wholly or chiefly of the <i lang="la" xml:lang="la">a priori</i> 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<span class="pagenum" title="313"><a name="Page_313" id="Page_313"></a></span> +instance, and there are still other points in morality which +are claimed as ideals at least by a great majority of moral +thinkers.</p> + +<p>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 +<em>might</em> come to an end in <em>one</em> 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 <span class="nowrap">evolution.<a name="FNanchor_165_165" id="FNanchor_165_165"></a><a href="#Footnote_165_165" class="fnanchor">165</a></span></p> + +<p>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 <em>not one</em>, 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<span class="pagenum" title="314"><a name="Page_314" id="Page_314"></a></span> +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 <em>one</em> +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 <em>necessarily</em> be an +“evolution.” Even then the paths taken by different +individuals or different branches of the human race on their +way to redemption <em>can</em> be regarded as independent lines.</p> + +<p>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.</p> + +<p>All this, of course, is not to be understood to affirm +that there never <em>will</em> be discovered any real evolutionary +element in human history—in the so-called <span class="pagenum" title="315"><a name="Page_315" id="Page_315"></a></span>“subconscious” +sphere perhaps—but at present we certainly are ignorant +of such an element.</p> + + +<p class="tac pt12b02em"><span class="lowercase smcap">THE PROBLEM OF THE “SINGLE” AS SUCH</span></p> + +<p>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 <em>for</em> individual psychology but not <em>as</em> +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.</p> + +<p>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.</p> + +<p>As a matter of fact, such new reasoning has been tried, +and <span class="nowrap">Rickert,<a name="FNanchor_166_166" id="FNanchor_166_166"></a><a href="#Footnote_166_166" class="fnanchor">166</a></span> 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<span class="pagenum" title="316"><a name="Page_316" id="Page_316"></a></span> +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”?</p> + +<p>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 <em>actual and true specification</em> 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.</p> + +<p>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 <em>unit</em> in reality: as +soon as it was that, it would have become a logical<span class="pagenum" title="317"><a name="Page_317" id="Page_317"></a></span> +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.</p> + +<p>But what importance does Rickert attach to his history +specified and non-repeatably single?</p> + +<p>History has a logic of its own, he says; the scheme +of its logic is not the syllogism, but the <em>relation to “values.”</em> +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?</p> + +<p>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?</p> + +<p>The relation to values is not to include any kind of +“Bewertung” of judgment, Rickert allows. In fact, history<span class="pagenum" title="318"><a name="Page_318" id="Page_318"></a></span> +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.</p> + +<p>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.</p> + +<p>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<span class="pagenum" title="319"><a name="Page_319" id="Page_319"></a></span> +must bear some relation in order to become important +historically.</p> + +<p>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?</p> + +<p>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 <em>any</em> 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 +<span class="nowrap">universality<a name="FNanchor_167_167" id="FNanchor_167_167"></a><a href="#Footnote_167_167" class="fnanchor">167</a></span> 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 <i lang="la" xml:lang="la">consensus omnium</i> with +regard to these “values.”</p> + +<p>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 <em>interests</em> him +personally.</p> + +<p>Here now we have met definitively the ambiguous +word: history indeed is to end in “interest” and in being<span class="pagenum" title="320"><a name="Page_320" id="Page_320"></a></span> +“interesting.” There is nothing like a real “value” in +any sense underlying history; the word <em>value</em> 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 <span class="nowrap">history.<a name="FNanchor_168_168" id="FNanchor_168_168"></a><a href="#Footnote_168_168" class="fnanchor">168</a></span></p> + +<p>And it follows that history as regarded by Rickert cannot +serve as the preliminary to philosophy. It <em>may</em> <span class="nowrap">be<a name="FNanchor_169_169" id="FNanchor_169_169"></a><a href="#Footnote_169_169" class="fnanchor">169</a></span> 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.</p> + +<p>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 <em>instances</em> +of certain types of actions and occurrences which have been<span class="pagenum" title="321"><a name="Page_321" id="Page_321"></a></span> +proved to be “valuable,” <i>i.e.</i> 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 <em>any</em> “values” whatever—if +there were any generally conceded—would become +“non-historical” just as well: for the <em>generalities</em> 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.</p> + +<p>The “limits of concepts in natural sciences” then are +the same as the limits of <em>intellectual</em> concepts in general. +For intellectual, <i>i.e.</i> 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.</p> + +<hr class="short" /> + +<p><span class="pagenum" title="322"><a name="Page_322" id="Page_322"></a></span></p> + + + + +<h3><span class="smcap">Conclusions about Systematics and History in +General</span></h3> + + +<p>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.</p> + +<p>What we have learnt from this analysis, though certainly +important in itself, has not afforded us any new result for +theoretical biology.</p> + +<p>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.</p> + +<p>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.</p> + +<p>We now leave the theory of human history, which has +been to us nothing more than a branch of biological<span class="pagenum" title="323"><a name="Page_323" id="Page_323"></a></span> +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 <em>about</em> 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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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,<span class="pagenum" title="324"><a name="Page_324" id="Page_324"></a></span> +taken by themselves, could only be of practical or emotional +interest.</p> + +<p>Thus it is from the study of the living <em>individual</em> 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.</p> + +<hr class="chap" /> + +<p><span class="pagenum" title="325"><a name="Page_325" id="Page_325"></a></span></p> + + + + +<h2>INDEX</h2> + + +<p> +Absolute, <a href="#Page_5">5</a><br /> +Acclimatisation, <a href="#Page_191">191</a><br /> +Acquired characters, <a href="#Page_217">217</a>, <a href="#Page_276">276</a> f.<br /> +Adaptation (definition), <a href="#Page_166">166</a>, <a href="#Page_171">171</a>, <a href="#Page_185">185</a><br /> +<span class="ml1em">to changes from without, <a href="#Page_172">172</a> ff.</span><br /> +<span class="ml1em">functional, <a href="#Page_114">114</a>, <a href="#Page_176">176</a> ff.</span><br /> +<span class="ml1em">and Lamarckism, <a href="#Page_272">272</a>, <a href="#Page_280">280</a></span><br /> +<span class="ml1em">mechanical, <a href="#Page_177">177</a> f.</span><br /> +<span class="ml1em">morphological, <a href="#Page_168">168</a> ff.</span><br /> +<span class="ml1em">physiological, <a href="#Page_184">184</a> ff.</span><br /> +<span class="ml1em">primary and secondary, <a href="#Page_188">188</a> f.</span><br /> +Adaptedness, <a href="#Page_186">186</a> f.<br /> +<i>Adiantum</i>, <a href="#Page_279">279</a><br /> +Adventitious, <a href="#Page_55">55</a>, <a href="#Page_74">74</a>, <a href="#Page_111">111</a>, <a href="#Page_221">221</a><br /> +Albumen, <a href="#Page_200">200</a><br /> +Allelomorphs, <a href="#Page_231">231</a><br /> +Amphibious plants, <a href="#Page_172">172</a> ff.<br /> +Annelids, <a href="#Page_65">65</a>, <a href="#Page_70">70</a>, <a href="#Page_221">221</a><br /> +Answering reaction, <a href="#Page_181">181</a><br /> +Anti-bodies, <a href="#Page_206">206</a> f.<br /> +Antitoxins, <a href="#Page_207">207</a> f.<br /> +<i>A priori</i>, <a href="#Page_6">6</a><br /> +Aristotle, <a href="#Page_144">144</a><br /> +<i>Ascaris</i>, <a href="#Page_93">93</a><br /> +<i>Aspergillus</i>, <a href="#Page_195">195</a><br /> +Assimilation, <a href="#Page_17">17</a><br /> +Atrophy, <a href="#Page_178">178</a><br /> +Autonomy of life, <a href="#Page_143">143</a>, <a href="#Page_224">224</a> f., <a href="#Page_324">324</a><br /> +<br /> +Babák, <a href="#Page_177">177</a><br /> +Baer, C. E. v., <a href="#Page_48">48</a> f. 282<br /> +Bateson, <a href="#Page_229">229</a> ff., <a href="#Page_238">238</a><br /> +Bayliss, <a href="#Page_204">204</a>, <a href="#Page_212">212</a><br /> +<i>Begonia</i>, <a href="#Page_221">221</a><br /> +Bergson, <a href="#Page_305">305</a><br /> +Berkeley, <a href="#Page_6">6</a><br /> +Berthold, <a href="#Page_91">91</a><br /> +Biogenetisches Grundgesetz, <a href="#Page_248">248</a><br /> +Biology, <a href="#Page_8">8</a> ff., <a href="#Page_15">15</a> f.<br /> +Blaringhem, <a href="#Page_238">238</a>, <a href="#Page_276">276</a><br /> +Blastoderm, <a href="#Page_39">39</a><br /> +Blastomeres, <a href="#Page_36">36</a>, <a href="#Page_59">59</a>, <a href="#Page_61">61</a> f., <a href="#Page_79">79</a><br /> +Blastula, <a href="#Page_37">37</a>, <a href="#Page_61">61</a>, <a href="#Page_79">79</a><br /> +Blumenbach, <a href="#Page_26">26</a><br /> +Boirivant, <a href="#Page_174">174</a><br /> +Bonnet, <a href="#Page_26">26</a><br /> +Boveri, <a href="#Page_29">29</a>, <a href="#Page_60">60</a>, <a href="#Page_95">95</a>, <a href="#Page_235">235</a> f.<br /> +Buckle, <a href="#Page_308">308</a>, <a href="#Page_310">310</a><br /> +Bunge, v., <a href="#Page_248">248</a><br /> +Bütschli, <a href="#Page_91">91</a><br /> +<br /> +Calcium, <a href="#Page_97">97</a><br /> +Calkins, <a href="#Page_33">33</a><br /> +Cambium, <a href="#Page_120">120</a>, <a href="#Page_183">183</a>, <a href="#Page_220">220</a><br /> +Catalysis, <a href="#Page_164">164</a>, <a href="#Page_203">203</a><br /> +Categories, <a href="#Page_6">6</a> f.<br /> +Cause, <a href="#Page_99">99</a> ff.<br /> +Cell, <a href="#Page_27">27</a> f.<br /> +<span class="ml1em">-division, <a href="#Page_28">28</a> ff., <a href="#Page_53">53</a>, <a href="#Page_94">94</a></span><br /> +<span class="ml1em">-lineage, <a href="#Page_58">58</a>, <a href="#Page_70">70</a></span><br /> +<span class="ml1em">-theory, <a href="#Page_27">27</a> f.</span><br /> +Chemical theory (of morphogenesis), <a href="#Page_134">134</a> ff.<br /> +Chemistry, systematics of, <a href="#Page_244">244</a>.<br /> +Child, C. M., <a href="#Page_180">180</a><br /> +Chromatic regulations, <a href="#Page_197">197</a><br /> +Chromatin, <a href="#Page_28">28</a> f.<br /> +Chromosomes, <a href="#Page_30">30</a>, <a href="#Page_237">237</a><br /> +Chun, <a href="#Page_66">66</a><br /> +Classification, <a href="#Page_246">246</a> f.<br /> +<i>Clavellina</i>, <a href="#Page_129">129</a>, <a href="#Page_154">154</a>, <a href="#Page_162">162</a> f.<br /> +Cleavage, <a href="#Page_35">35</a> ff., <a href="#Page_53">53</a>, <a href="#Page_58">58</a>, <a href="#Page_60">60</a>, <a href="#Page_63">63</a>, <a href="#Page_71">71</a>, <a href="#Page_92">92</a><br /> +Colloids, <a href="#Page_187">187</a><br /> +Compensatory process, <a href="#Page_112">112</a><br /> +Complex potencies, <a href="#Page_112">112</a>, <a href="#Page_120">120</a><br /> +Conic sections, <a href="#Page_243">243</a><br /> +Conjugation, <a href="#Page_33">33</a><br /> +Conklin, <a href="#Page_86">86</a><br /> +Contingency, <a href="#Page_218">218</a>, <a href="#Page_284">284</a> ff. 304<br /> +Continuity of germ-plasm, <a href="#Page_215">215</a>, <a href="#Page_227">227</a><br /> +<span class="pagenum" title="326"><a name="Page_326" id="Page_326"></a></span><br /> +Cope, <a href="#Page_273">273</a><br /> +Correlation (of masses), <a href="#Page_93">93</a><br /> +<span class="ml1em">(of parts), <a href="#Page_247">247</a></span><br /> +Correns, <a href="#Page_228">228</a><br /> +Crampton, <a href="#Page_70">70</a> f.<br /> +Crayfish, <a href="#Page_105">105</a><br /> +Ctenophores, <a href="#Page_66">66</a><br /> +Cumulation, <a href="#Page_301">301</a> ff., <a href="#Page_308">308</a> ff., <a href="#Page_314">314</a>, <a href="#Page_317">317</a><br /> +Cuvier, <a href="#Page_247">247</a><br /> +<br /> +Darwin, Ch., <a href="#Page_260">260</a> ff., <a href="#Page_271">271</a>, <a href="#Page_283">283</a><br /> +Darwinism, <a href="#Page_260">260</a> ff., <a href="#Page_271">271</a>, <a href="#Page_283">283</a> ff., <a href="#Page_293">293</a> ff., <a href="#Page_304">304</a><br /> +Davenport, <a href="#Page_191">191</a>, <a href="#Page_206">206</a><br /> +Delage, <a href="#Page_32">32</a><br /> +Descent, theory of, <a href="#Page_250">250</a> ff.<br /> +Description, <a href="#Page_12">12</a>, <a href="#Page_50">50</a><br /> +Detto, <a href="#Page_172">172</a><br /> +Directive stimuli, <a href="#Page_102">102</a> ff.<br /> +Doncaster, <a href="#Page_232">232</a><br /> +Dreyer, <a href="#Page_92">92</a><br /> +<br /> +<i><a id="Echinus"></a>Echinus</i>, <a href="#Page_27">27</a>, <a href="#Page_33">33</a> ff., <a href="#Page_60">60</a> ff., <a href="#Page_68">68</a>, <a href="#Page_81">81</a>, <a href="#Page_85">85</a>, <a href="#Page_87">87</a>, <a href="#Page_98">98</a>, <a href="#Page_104">104</a>, <a href="#Page_108">108</a>, <a href="#Page_111">111</a>, <a href="#Page_154">154</a>, <a href="#Page_232">232</a>, <a href="#Page_235">235</a><br /> +Ectoderm, <a href="#Page_41">41</a>, <a href="#Page_81">81</a>, <a href="#Page_122">122</a><br /> +Egg, <a href="#Page_31">31</a>, <a href="#Page_33">33</a> f.<br /> +Ehrlich, <a href="#Page_207">207</a> f.<br /> +Eimer, <a href="#Page_292">292</a><br /> +Elementary organs, <a href="#Page_46">46</a> ff.<br /> +<span class="ml1em">processes, <a href="#Page_46">46</a> ff.</span><br /> +Elements of nature, <a href="#Page_9">9</a><br /> +Embryo, <a href="#Page_44">44</a><br /> +<span class="ml1em">frog’s, <a href="#Page_59">59</a>, <a href="#Page_65">65</a>, <a href="#Page_67">67</a></span><br /> +<span class="ml1em">half, <a href="#Page_59">59</a>, <a href="#Page_61">61</a>, <a href="#Page_66">66</a> ff.</span><br /> +<span class="ml1em">whole, <a href="#Page_61">61</a>, <a href="#Page_67">67</a> f.</span><br /> +Endoderm, <a href="#Page_41">41</a>, <a href="#Page_81">81</a><br /> +Entelechy, <a href="#Page_143">143</a> f., <a href="#Page_224">224</a> f., <a href="#Page_295">295</a><br /> +Entwickelungsmechanik, <a href="#Page_57">57</a>, <a href="#Page_70">70</a>, <a href="#Page_78">78</a>, <a href="#Page_241">241</a><br /> +Enumeration, <a href="#Page_297">297</a>, <a href="#Page_300">300</a><br /> +Enzymes, <a href="#Page_164">164</a>, <a href="#Page_203">203</a><br /> +Epigenesis, <a href="#Page_26">26</a>, <a href="#Page_45">45</a>, <a href="#Page_54">54</a>, <a href="#Page_72">72</a>, <a href="#Page_144">144</a>, <a href="#Page_301">301</a><br /> +Equifinality (of restitutions), <a href="#Page_159">159</a> f.<br /> +Equipotential, <a href="#Page_83">83</a><br /> +Eschenhagen, <a href="#Page_195">195</a><br /> +Evolutio, <a href="#Page_26">26</a>, <a href="#Page_45">45</a> f., <a href="#Page_54">54</a>, <a href="#Page_59">59</a>, <a href="#Page_61">61</a>, <a href="#Page_64">64</a>, <a href="#Page_72">72</a>, <a href="#Page_144">144</a>, <a href="#Page_205">205</a>, <a href="#Page_301">301</a><br /> +Evolution, <a href="#Page_8">8</a>, <a href="#Page_21">21</a>, <a href="#Page_46">46</a>, <a href="#Page_250">250</a>, <a href="#Page_301">301</a>, <a href="#Page_305">305</a>, <a href="#Page_311">311</a> ff., <a href="#Page_317">317</a><br /> +Experience, <a href="#Page_7">7</a> f., <a href="#Page_12">12</a>, <a href="#Page_212">212</a><br /> +Experiment, <a href="#Page_51">51</a>, <a href="#Page_56">56</a> f.<br /> +“Explaining,” 51, <a href="#Page_309">309</a><br /> +Explicit potency, <a href="#Page_84">84</a><br /> +<br /> +Fasting, <a href="#Page_199">199</a> f.<br /> +Ferments, <a href="#Page_164">164</a>, <a href="#Page_203">203</a> f.<br /> +Fertilisation, <a href="#Page_32">32</a> ff.<br /> +Fischer, <a href="#Page_278">278</a><br /> +Foges, <a href="#Page_107">107</a><br /> +Form, closed or open, <a href="#Page_49">49</a><br /> +Form, organic, specific, <a href="#Page_16">16</a> ff., <a href="#Page_25">25</a>, <a href="#Page_92">92</a>, <a href="#Page_293">293</a> ff.<br /> +Forma accidentalis, <a href="#Page_293">293</a><br /> +<span class="ml1em">essentialis, <a href="#Page_294">294</a> f.</span><br /> +Formative stimuli, <a href="#Page_102">102</a> ff., <a href="#Page_113">113</a>, <a href="#Page_118">118</a>, <a href="#Page_133">133</a><br /> +Francé, <a href="#Page_158">158</a>, <a href="#Page_239">239</a><br /> +Frédéricq, <a href="#Page_196">196</a><br /> +Frog, embryo of, <a href="#Page_59">59</a>, <a href="#Page_65">65</a>, <a href="#Page_67">67</a><br /> +Fromm, <a href="#Page_205">205</a><br /> +Function (mathematical), <a href="#Page_80">80</a><br /> +Fungi, metabolism of, <a href="#Page_201">201</a><br /> +<br /> +Gaidukow, <a href="#Page_197">197</a> f.<br /> +Galls, <a href="#Page_101">101</a><br /> +Galton, <a href="#Page_228">228</a>, <a href="#Page_238">238</a><br /> +Gamble and Keeble, <a href="#Page_198">198</a><br /> +Gastrula, <a href="#Page_41">41</a>, <a href="#Page_61">61</a>, <a href="#Page_81">81</a><br /> +Gautier, <a href="#Page_239">239</a><br /> +Geographical distribution, <a href="#Page_251">251</a> f.<br /> +Geometry, solid, <a href="#Page_243">243</a><br /> +Germ-layers, <a href="#Page_41">41</a>, <a href="#Page_44">44</a>, <a href="#Page_61">61</a><br /> +<span class="ml1em">-lineage, <a href="#Page_215">215</a></span><br /> +<span class="ml1em">-plasm, <a href="#Page_52">52</a>, <a href="#Page_215">215</a></span><br /> +Gifford, Lord, <a href="#Page_1">1</a> ff., <a href="#Page_322">322</a><br /> +Godlewski, <a href="#Page_105">105</a>, <a href="#Page_155">155</a>, <a href="#Page_235">235</a><br /> +Goebel, <a href="#Page_116">116</a><br /> +Goethe, <a href="#Page_247">247</a><br /> +Goette, <a href="#Page_48">48</a>, <a href="#Page_56">56</a>, <a href="#Page_214">214</a><br /> +Goltz, <a href="#Page_181">181</a><br /> +Growth, <a href="#Page_30">30</a>, <a href="#Page_93">93</a> f.<br /> +Gruber, <a href="#Page_236">236</a><br /> +<br /> +Haeckel, <a href="#Page_37">37</a>, <a href="#Page_41">41</a><br /> +Half-embryo, <a href="#Page_59">59</a>, <a href="#Page_61">61</a>, <a href="#Page_66">66</a> ff.<br /> +Haller, A. v., <a href="#Page_26">26</a><br /> +Harmony, <a href="#Page_107">107</a> ff., <a href="#Page_117">117</a>, <a href="#Page_295">295</a><br /> +Hausmann, <a href="#Page_206">206</a><br /> +Heat production, <a href="#Page_193">193</a><br /> +Hegel, <a href="#Page_307">307</a>, <a href="#Page_311">311</a> ff.<br /> +Herbst, <a href="#Page_96">96</a> ff., <a href="#Page_102">102</a>, <a href="#Page_104">104</a> ff., <a href="#Page_172">172</a>, <a href="#Page_177">177</a>, <a href="#Page_200">200</a>, <a href="#Page_232">232</a>, <a href="#Page_236">236</a><br /> +Heredity, <a href="#Page_21">21</a>, <a href="#Page_52">52</a><br /> +Hering, <a href="#Page_216">216</a> f.<br /> +Hertwig, O., <a href="#Page_60">60</a>, <a href="#Page_65">65</a><br /> +Hertwig, R., <a href="#Page_32">32</a> f., <a href="#Page_60">60</a>, <a href="#Page_107">107</a><br /> +His, <a href="#Page_56">56</a>, <a href="#Page_93">93</a><br /> +History, <a href="#Page_2">2</a>, <a href="#Page_14">14</a>, <a href="#Page_21">21</a>, <a href="#Page_250">250</a>, <a href="#Page_257">257</a>, <a href="#Page_297">297</a> ff.<br /> +<span class="ml1em">of mankind, <a href="#Page_306">306</a> ff.</span><br /> +Holmes, <a href="#Page_180">180</a><br /> +Hume, <a href="#Page_6">6</a><br /> +Hypertrophy, <a href="#Page_112">112</a>, <a href="#Page_114">114</a><br /> +Hypertypy, <a href="#Page_112">112</a><br /> +<span class="pagenum" title="327"><a name="Page_327" id="Page_327"></a></span><br /> +Idealism, <a href="#Page_5">5</a>, <a href="#Page_7">7</a><br /> +Immunity, <a href="#Page_204">204</a> ff.<br /> +Implicit potency, <a href="#Page_84">84</a><br /> +Improvement (of morphogenesis), <a href="#Page_212">212</a><br /> +Indifferent cells, <a href="#Page_182">182</a><br /> +Inflammation, <a href="#Page_206">206</a><br /> +Inheritance, <a href="#Page_35">35</a>, <a href="#Page_214">214</a> ff.<br /> +<span class="ml1em">of acquired characters, <a href="#Page_217">217</a>, <a href="#Page_275">275</a> ff., <a href="#Page_290">290</a></span><br /> +Irritability, <a href="#Page_190">190</a> ff.<br /> +<br /> +Jacoby, <a href="#Page_207">207</a><br /> +Jaeger, <a href="#Page_214">214</a><br /> +Jennings, <a href="#Page_218">218</a><br /> +<br /> +Kammerer, <a href="#Page_176">176</a>, <a href="#Page_280">280</a><br /> +Kant, <a href="#Page_6">6</a> f.<br /> +Kirchhoff, <a href="#Page_50">50</a><br /> +Klebs, <a href="#Page_96">96</a>, <a href="#Page_170">170</a>, <a href="#Page_180">180</a>, <a href="#Page_238">238</a>, <a href="#Page_276">276</a><br /> +Kölliker, <a href="#Page_292">292</a><br /> +Korshinsky, <a href="#Page_239">239</a><br /> +Krašan, <a href="#Page_221">221</a>, <a href="#Page_251">251</a><br /> +<br /> +Lamarck, <a href="#Page_271">271</a> f., <a href="#Page_291">291</a><br /> +Lamarckism, <a href="#Page_271">271</a> f., <a href="#Page_284">284</a> ff., <a href="#Page_293">293</a> ff., <a href="#Page_304">304</a><br /> +Lamprecht, <a href="#Page_308">308</a>, <a href="#Page_310">310</a><br /> +Larva, <a href="#Page_41">41</a> f., <a href="#Page_44">44</a><br /> +Law of nature, <a href="#Page_13">13</a>, <a href="#Page_16">16</a><br /> +Leibniz, <a href="#Page_6">6</a><br /> +Lens (of eye), <a href="#Page_105">105</a>, <a href="#Page_221">221</a><br /> +Liebmann, <a href="#Page_256">256</a><br /> +Life, <a href="#Page_9">9</a> f., <a href="#Page_16">16</a>, <a href="#Page_21">21</a><br /> +Lillie, R. S., <a href="#Page_236">236</a><br /> +Limits of regulability, <a href="#Page_212">212</a><br /> +Lithium, <a href="#Page_99">99</a><br /> +“Living,” 9, <a href="#Page_16">16</a><br /> +Localisation, <a href="#Page_101">101</a>, <a href="#Page_103">103</a>, <a href="#Page_118">118</a> ff.<br /> +Locke, <a href="#Page_6">6</a><br /> +Loeb, J., <a href="#Page_32">32</a>, <a href="#Page_102">102</a>, <a href="#Page_164">164</a>, <a href="#Page_179">179</a>, <a href="#Page_196">196</a>, <a href="#Page_236">236</a><br /> +Loeb, L., <a href="#Page_208">208</a><br /> +Lyon, <a href="#Page_87">87</a><br /> +<br /> +MacDougal, <a href="#Page_238">238</a> f., <a href="#Page_276">276</a><br /> +Machine (definition), <a href="#Page_139">139</a><br /> +Machine-theory of life, <a href="#Page_138">138</a> ff., <a href="#Page_187">187</a>, <a href="#Page_210">210</a><br /> +Maillard, <a href="#Page_196">196</a><br /> +Manifoldness, <a href="#Page_25">25</a> f., <a href="#Page_30">30</a>, <a href="#Page_45">45</a><br /> +<span class="ml1em">intensive, <a href="#Page_144">144</a></span><br /> +Materialism, <a href="#Page_283">283</a><br /> +Materials, transport of, <a href="#Page_194">194</a><br /> +Matter, theory of, <a href="#Page_8">8</a><br /> +Maturation, <a href="#Page_31">31</a>, <a href="#Page_87">87</a><br /> +Mayenburg, v., <a href="#Page_195">195</a><br /> +Means, of morphogenesis, <a href="#Page_89">89</a> ff., <a href="#Page_101">101</a>, <a href="#Page_113">113</a>, <a href="#Page_118">118</a>, <a href="#Page_228">228</a>, <a href="#Page_234">234</a><br /> +Memory, <a href="#Page_216">216</a> f.<br /> +Mendel, <a href="#Page_229">229</a> f.<br /> +Merrifield, <a href="#Page_198">198</a><br /> +Mesenchyme, <a href="#Page_39">39</a>, <a href="#Page_41">41</a>, <a href="#Page_104">104</a>, <a href="#Page_111">111</a>, <a href="#Page_151">151</a> f.<br /> +Metabolic regulations, <a href="#Page_198">198</a> f.<br /> +Metabolism, <a href="#Page_16">16</a>, <a href="#Page_184">184</a><br /> +<span class="ml1em">of fungi, <a href="#Page_201">201</a></span><br /> +Metschnikoff, <a href="#Page_206">206</a><br /> +Micromeres, <a href="#Page_36">36</a>, <a href="#Page_60">60</a><br /> +Miehe, <a href="#Page_116">116</a><br /> +Mill, J. S., <a href="#Page_57">57</a><br /> +<i>Mimosa</i>, <a href="#Page_191">191</a><br /> +Minkiewicz, <a href="#Page_198">198</a><br /> +Modification, <a href="#Page_277">277</a><br /> +Molluscs, <a href="#Page_70">70</a> f., <a href="#Page_86">86</a><br /> +Morgan, T. H., <a href="#Page_32">32</a>, <a href="#Page_66">66</a> f., <a href="#Page_95">95</a>, <a href="#Page_107">107</a>, <a href="#Page_114">114</a> f., <a href="#Page_162">162</a>, <a href="#Page_230">230</a><br /> +Morphaesthesia, <a href="#Page_157">157</a><br /> +Morphogenesis, <a href="#Page_20">20</a>, <a href="#Page_52">52</a>, <a href="#Page_76">76</a>, <a href="#Page_112">112</a>, <a href="#Page_118">118</a> f.<br /> +Morphology, <a href="#Page_12">12</a><br /> +Movements, organic, <a href="#Page_17">17</a><br /> +Mutations, <a href="#Page_237">237</a> f., <a href="#Page_276">276</a>, <a href="#Page_291">291</a><br /> +<br /> +Nägeli, <a href="#Page_266">266</a>, <a href="#Page_292">292</a><br /> +Nathansohn, <a href="#Page_196">196</a><br /> +Natural selection, <a href="#Page_261">261</a> f., <a href="#Page_290">290</a><br /> +Nature, <a href="#Page_5">5</a> ff.<br /> +Němec, <a href="#Page_116">116</a><br /> +Newport, <a href="#Page_57">57</a><br /> +Newt (regeneration of), <a href="#Page_155">155</a>, <a href="#Page_221">221</a> f.<br /> +Noll, <a href="#Page_146">146</a>, <a href="#Page_157">157</a> f.<br /> +Nomothetic, <a href="#Page_14">14</a> f.<br /> +Normal, <a href="#Page_78">78</a><br /> +Nuclear division, <a href="#Page_28">28</a> f., <a href="#Page_62">62</a>, <a href="#Page_64">64</a> f., <a href="#Page_72">72</a>, <a href="#Page_235">235</a><br /> +Nucleus, <a href="#Page_28">28</a>, <a href="#Page_35">35</a><br /> +<span class="ml1em">rôle of nucleus in inheritance, <a href="#Page_233">233</a> f.</span><br /> +<br /> +Organ-forming substances, <a href="#Page_117">117</a><br /> +<i>Oscillariae</i>, <a href="#Page_197">197</a><br /> +Osmotic pressure, <a href="#Page_93">93</a>, <a href="#Page_187">187</a>, <a href="#Page_194">194</a> f.<br /> +Overton, <a href="#Page_196">196</a> f.<br /> +Oxidation, rôle of, <a href="#Page_198">198</a> f.<br /> +<br /> +Palaeontology, <a href="#Page_252">252</a><br /> +Parallelism (psycho-physical), <a href="#Page_146">146</a><br /> +Parthenogenesis, <a href="#Page_32">32</a><br /> +Pauly, <a href="#Page_146">146</a>, <a href="#Page_217">217</a>, <a href="#Page_273">273</a> f.<br /> +Pawlow, <a href="#Page_204">204</a>, <a href="#Page_210">210</a>, <a href="#Page_212">212</a><br /> +Pearl, R., <a href="#Page_212">212</a><br /> +Pfeffer, <a href="#Page_195">195</a>, <a href="#Page_201">201</a><br /> +Phagocytosis, <a href="#Page_206">206</a><br /> +Phenomenon, <a href="#Page_5">5</a> f.<br /> +Philosophy, natural, <a href="#Page_4">4</a><br /> +<span class="ml1em">of nature, <a href="#Page_4">4</a>, <a href="#Page_7">7</a>, <a href="#Page_9">9</a></span><br /> +<span class="ml1em">of the organism, <a href="#Page_9">9</a>, <a href="#Page_15">15</a></span><br /> +Phylogeny, <a href="#Page_255">255</a>, <a href="#Page_291">291</a>, <a href="#Page_297">297</a>, <a href="#Page_304">304</a> ff.<br /> +<span class="pagenum" title="328"><a name="Page_328" id="Page_328"></a></span><br /> +Physiology, <a href="#Page_12">12</a><br /> +<span class="ml1em">of development (morphogenesis), <a href="#Page_20">20</a></span><br /> +<i>Planaria</i>, <a href="#Page_130">130</a>, <a href="#Page_155">155</a>, <a href="#Page_162">162</a> f., <a href="#Page_200">200</a><br /> +Plants, <a href="#Page_48">48</a> f.<br /> +Plato, <a href="#Page_2">2</a><br /> +Pluteus, <a href="#Page_42">42</a><br /> +Poisons, <a href="#Page_205">205</a> ff.<br /> +Pole, <a href="#Page_36">36</a><br /> +Polarity, <a href="#Page_106">106</a><br /> +Potencies, complex, <a href="#Page_112">112</a>, <a href="#Page_120">120</a><br /> +<span class="ml1em">explicit, <a href="#Page_84">84</a></span><br /> +<span class="ml1em">implicit, <a href="#Page_84">84</a></span><br /> +<span class="ml1em">primary, <a href="#Page_84">84</a>, <a href="#Page_111">111</a></span><br /> +<span class="ml1em">prospective, <a href="#Page_77">77</a> ff., <a href="#Page_83">83</a>, <a href="#Page_89">89</a>, <a href="#Page_118">118</a>, <a href="#Page_125">125</a>, <a href="#Page_241">241</a></span><br /> +<span class="ml1em">secondary, <a href="#Page_84">84</a>, <a href="#Page_110">110</a></span><br /> +Poulton, <a href="#Page_198">198</a><br /> +Precipitin, <a href="#Page_207">207</a> f.<br /> +Pressure experiments, <a href="#Page_63">63</a>, <a href="#Page_141">141</a><br /> +Primary potency, <a href="#Page_84">84</a>, <a href="#Page_111">111</a><br /> +<span class="ml1em">purposefulness, <a href="#Page_146">146</a>, <a href="#Page_287">287</a></span><br /> +<span class="ml1em">regulation, <a href="#Page_85">85</a>, <a href="#Page_174">174</a>, <a href="#Page_188">188</a></span><br /> +Progress, <a href="#Page_305">305</a><br /> +Pronuclei, <a href="#Page_55">55</a><br /> +Prospective potency, <a href="#Page_77">77</a> ff., <a href="#Page_83">83</a>, <a href="#Page_89">89</a>, <a href="#Page_118">118</a>, <a href="#Page_125">125</a>, <a href="#Page_241">241</a><br /> +<span class="ml1em">value, <a href="#Page_77">77</a> f., <a href="#Page_80">80</a>, <a href="#Page_122">122</a></span><br /> +Protista (Protozoa), <a href="#Page_27">27</a>, <a href="#Page_130">130</a>, <a href="#Page_236">236</a><br /> +Protoplasm, <a href="#Page_28">28</a>, <a href="#Page_30">30</a><br /> +<span class="ml1em">morphogenetic rôle of, <a href="#Page_67">67</a></span><br /> +Przibram, <a href="#Page_112">112</a>, <a href="#Page_248">248</a><br /> +<br /> +Rádl, <a href="#Page_247">247</a><br /> +Rauber, <a href="#Page_235">235</a><br /> +Reaction, answering, <a href="#Page_181">181</a><br /> +Reciprocity of harmony, <a href="#Page_156">156</a> f.<br /> +Re-differentiation, <a href="#Page_75">75</a>, <a href="#Page_111">111</a>, <a href="#Page_163">163</a><br /> +Regeneration, <a href="#Page_55">55</a>, <a href="#Page_74">74</a>, <a href="#Page_105">105</a>, <a href="#Page_111">111</a>, <a href="#Page_221">221</a><br /> +<span class="ml1em">super-, <a href="#Page_115">115</a> f.</span><br /> +Regulation, <a href="#Page_68">68</a>, <a href="#Page_73">73</a>, <a href="#Page_85">85</a>, <a href="#Page_111">111</a>, <a href="#Page_165">165</a><br /> +<span class="ml1em">defined, <a href="#Page_166">166</a></span><br /> +<span class="ml1em">metabolic, <a href="#Page_198">198</a> f.</span><br /> +<span class="ml1em">secondary, <a href="#Page_85">85</a>, <a href="#Page_165">165</a>, <a href="#Page_188">188</a></span><br /> +Reinke, <a href="#Page_146">146</a><br /> +Restitution, <a href="#Page_21">21</a>, <a href="#Page_74">74</a>, <a href="#Page_110">110</a>, <a href="#Page_112">112</a> ff.<br /> +<span class="ml1em">defined, <a href="#Page_166">166</a></span><br /> +<span class="ml1em">and Darwinism, <a href="#Page_267">267</a></span><br /> +<span class="ml1em">and Lamarckism, <a href="#Page_286">286</a></span><br /> +<span class="ml1em">of second order, <a href="#Page_158">158</a></span><br /> +Retina, <a href="#Page_191">191</a><br /> +Retro-differentiation, <a href="#Page_163">163</a> f.<br /> +Rhumbler, <a href="#Page_93">93</a><br /> +Ribbert, <a href="#Page_114">114</a><br /> +Rickert, <a href="#Page_315">315</a> ff.<br /> +Roux, <a href="#Page_26">26</a>, <a href="#Page_48">48</a>, <a href="#Page_55">55</a> ff., <a href="#Page_66">66</a> f., <a href="#Page_76">76</a>, <a href="#Page_89">89</a>, <a href="#Page_92">92</a> f., <a href="#Page_108">108</a>, <a href="#Page_161">161</a>, <a href="#Page_176">176</a> f., <a href="#Page_241">241</a><br /> +Rubner, <a href="#Page_193">193</a><br /> +<br /> +Sachs, <a href="#Page_117">117</a><br /> +Sadebeck, <a href="#Page_279">279</a><br /> +<i>Salamandra</i>, <a href="#Page_175">175</a>, <a href="#Page_281">281</a><br /> +Schneider, <a href="#Page_146">146</a><br /> +Schultz, E., <a href="#Page_200">200</a><br /> +Schultze, O., <a href="#Page_67">67</a><br /> +Schwendener, <a href="#Page_177">177</a><br /> +Science, <a href="#Page_14">14</a>, <a href="#Page_297">297</a><br /> +<span class="ml1em">natural, <a href="#Page_1">1</a> ff.</span><br /> +<span class="ml1em">rational, <a href="#Page_12">12</a></span><br /> +Sea-urchin, <i>see</i> <a href="#Echinus">Echinus</a><br /> +Secondary potency, <a href="#Page_84">84</a>, <a href="#Page_110">110</a><br /> +<span class="ml1em">regulation, <a href="#Page_85">85</a>, <a href="#Page_165">165</a>, <a href="#Page_188">188</a></span><br /> +Secretion, internal, <a href="#Page_116">116</a>, <a href="#Page_200">200</a><br /> +Segmentation, <a href="#Page_35">35</a><br /> +Selective qualities (of tissues), <a href="#Page_186">186</a><br /> +Self-differentiation, <a href="#Page_108">108</a><br /> +Semon, <a href="#Page_216">216</a> f.<br /> +Sex, <a href="#Page_107">107</a><br /> +Single, the, <a href="#Page_315">315</a> ff.<br /> +Skeleton, <a href="#Page_40">40</a> ff., <a href="#Page_44">44</a>, <a href="#Page_47">47</a>, <a href="#Page_92">92</a><br /> +Spemann, <a href="#Page_105">105</a><br /> +Spermatozoon (spermia), <a href="#Page_32">32</a> ff.<br /> +Splitting (of hybrids), <a href="#Page_229">229</a> f.<br /> +Stahl, <a href="#Page_197">197</a><br /> +Standfuss, <a href="#Page_278">278</a><br /> +Starfish, <a href="#Page_44">44</a>, <a href="#Page_81">81</a>, <a href="#Page_122">122</a><br /> +Starling, E., <a href="#Page_116">116</a>, <a href="#Page_204">204</a>, <a href="#Page_212">212</a><br /> +<i>Stentor</i>, <a href="#Page_131">131</a><br /> +Stimuli, directive, <a href="#Page_102">102</a> ff.<br /> +<span class="ml1em">formative, <a href="#Page_102">102</a> ff., <a href="#Page_113">113</a>, <a href="#Page_118">118</a>, <a href="#Page_133">133</a></span><br /> +<span class="ml1em">of restitutions, <a href="#Page_113">113</a> f.</span><br /> +Structure of protoplasm, <a href="#Page_66">66</a>, <a href="#Page_69">69</a>, <a href="#Page_72">72</a> f. 85, <a href="#Page_88">88</a><br /> +Substance, living, <a href="#Page_17">17</a><br /> +Sumner, <a href="#Page_196">196</a><br /> +Super-regeneration, <a href="#Page_115">115</a> f.<br /> +Surface-tension, <a href="#Page_91">91</a><br /> +Sutton, <a href="#Page_230">230</a><br /> +Symmetry, <a href="#Page_39">39</a>, <a href="#Page_68">68</a>, <a href="#Page_70">70</a>, <a href="#Page_72">72</a>, <a href="#Page_89">89</a>, <a href="#Page_98">98</a><br /> +System, combined types of, <a href="#Page_153">153</a> ff.<br /> +<span class="ml1em">complex, <a href="#Page_219">219</a> f.</span><br /> +<span class="ml1em">complex-harmonious, <a href="#Page_155">155</a></span><br /> +<span class="ml1em">equipotential, <a href="#Page_120">120</a></span><br /> +<span class="ml1em">harmonious-equipotential, <a href="#Page_121">121</a> ff., <a href="#Page_151">151</a> f.</span><br /> +<span class="ml1em">mixed-equipotential, <a href="#Page_154">154</a></span><br /> +<span class="ml1em">morphogenetic, <a href="#Page_119">119</a> f., <a href="#Page_163">163</a>, <a href="#Page_241">241</a></span><br /> +Systematics, <a href="#Page_14">14</a> ff., <a href="#Page_21">21</a>, <a href="#Page_243">243</a> f., <a href="#Page_253">253</a>, <a href="#Page_264">264</a>, <a href="#Page_293">293</a>, <a href="#Page_296">296</a><br /> +<br /> +Taine, <a href="#Page_308">308</a>, <a href="#Page_310">310</a><br /> +Theology, natural, <a href="#Page_1">1</a> ff.<br /> +Thomson, J. A., <a href="#Page_16">16</a><br /> +Thymus, <a href="#Page_204">204</a><br /> +<span class="pagenum" title="329"><a name="Page_329" id="Page_329"></a></span><br /> +Thyroid, <a href="#Page_204">204</a><br /> +Tissue, <a href="#Page_38">38</a><br /> +Toxins, <a href="#Page_207">207</a> f.<br /> +Transformism, <a href="#Page_251">251</a><br /> +Truth, <a href="#Page_7">7</a><br /> +Tschermak, <a href="#Page_228">228</a><br /> +<i>Tubularia</i>, <a href="#Page_126">126</a> ff., <a href="#Page_133">133</a>, <a href="#Page_158">158</a> ff.<br /> +Type, <a href="#Page_48">48</a>, <a href="#Page_247">247</a> f., <a href="#Page_282">282</a>, <a href="#Page_291">291</a><br /> +<br /> +“Understanding” (historically), <a href="#Page_302">302</a><br /> +Universality, postulate of, <a href="#Page_148">148</a> f.<br /> +Universe, <a href="#Page_5">5</a><br /> +Univocality, principle of, <a href="#Page_161">161</a><br /> +<br /> +“Values,” 317 ff.<br /> +<span class="ml1em">prospective, <a href="#Page_77">77</a> f., <a href="#Page_80">80</a>, <a href="#Page_122">122</a></span><br /> +Variation, <a href="#Page_218">218</a>, <a href="#Page_237">237</a> f., <a href="#Page_276">276</a><br /> +Variation, fluctuating, contingent, <a href="#Page_264">264</a> f., <a href="#Page_273">273</a> f., <a href="#Page_282">282</a>, <a href="#Page_290">290</a><br /> +Vernon, <a href="#Page_232">232</a>, <a href="#Page_238">238</a><br /> +Vitalism, <a href="#Page_143">143</a>, <a href="#Page_145">145</a> f., <a href="#Page_210">210</a> f., <a href="#Page_224">224</a> f., <a href="#Page_234">234</a>, <a href="#Page_240">240</a> f., <a href="#Page_272">272</a>, <a href="#Page_277">277</a><br /> +Vöchting, <a href="#Page_174">174</a>, <a href="#Page_179">179</a> f., <a href="#Page_182">182</a>, <a href="#Page_221">221</a><br /> +Volition, acts of, <a href="#Page_274">274</a><br /> +Vries, de, <a href="#Page_228">228</a>, <a href="#Page_238">238</a> f.<br /> +<br /> +Wallace, <a href="#Page_292">292</a><br /> +Ward, J., <a href="#Page_8">8</a>, <a href="#Page_143">143</a><br /> +Weber, law of, <a href="#Page_191">191</a><br /> +Weinland, <a href="#Page_202">202</a><br /> +Weismann, <a href="#Page_33">33</a>, <a href="#Page_52">52</a> ff., <a href="#Page_58">58</a> f., <a href="#Page_72">72</a>, <a href="#Page_74">74</a> f., <a href="#Page_103">103</a>, <a href="#Page_111">111</a>, <a href="#Page_138">138</a>, <a href="#Page_214">214</a> f., <a href="#Page_237">237</a>, <a href="#Page_277">277</a> f.<br /> +Weldon, <a href="#Page_238">238</a><br /> +Whole, the, <a href="#Page_28">28</a>, <a href="#Page_80">80</a>, <a href="#Page_117">117</a><br /> +<span class="ml1em">-embryo, <a href="#Page_61">61</a>, <a href="#Page_67">67</a> f.</span><br /> +Wigand, <a href="#Page_255">255</a>, <a href="#Page_266">266</a>, <a href="#Page_292">292</a><br /> +Wilson, E. B., <a href="#Page_27">27</a>, <a href="#Page_65">65</a>, <a href="#Page_70">70</a> f., <a href="#Page_86">86</a> f., <a href="#Page_107">107</a><br /> +Windelband, <a href="#Page_13">13</a> f.<br /> +Winkler, <a href="#Page_116">116</a>, <a href="#Page_221">221</a><br /> +Winterstein, <a href="#Page_199">199</a><br /> +Wolff, C. F., <a href="#Page_26">26</a><br /> +Wolff, G., <a href="#Page_105">105</a>, <a href="#Page_146">146</a>, <a href="#Page_255">255</a>, <a href="#Page_266">266</a>, <a href="#Page_287">287</a> f.<br /> +Wolff, J., <a href="#Page_177">177</a><br /> +<br /> +Yung, <a href="#Page_177">177</a><br /> +<br /> +Zeleny, <a href="#Page_112">112</a>, <a href="#Page_115">115</a>, <a href="#Page_212">212</a><br /> +Zur Strassen, <a href="#Page_93">93</a> +</p> + + +<p class="tac fs65"><br /><br /><br /><br />THE END<br /><br /><br /><br /> + +<i>Printed by</i> <span class="smcap">R. & R. Clark, Limited,</span> <i>Edinburgh</i>.</p> + +<p><span class="pagenum hide" title="330"><a name="Page_330" id="Page_330"></a></span><br /><span class="pagenum hide" title="331"><a name="Page_331" id="Page_331"></a></span></p> + + + +<hr class="chap" /> + +<h2>HEREDITY AND SELECTION<br /> +IN SOCIOLOGY</h2> + + +<p class="tac fs65 pt12b02em">BY</p> + +<p class="tac fs120">G. CHATTERTON HILL</p> + +<p class="tac">Demy 8vo, Cloth, 600 pages.</p> + +<p class="tac">Price <b><span class="fs120">12s. 6d.</span></b> net.</p> + +<p class="tac"><i>Post Free, Price</i> <b><span class="fs120">12s. 11d.</span></b></p> + +<p class="tac pt12b02em">SOME PRESS OPINIONS</p> + +<div class="fs85 mlr10em"> +<p>“A most praiseworthy and suggestive work—should certainly be +studied by every serious thinker.”—<cite>Morning Post.</cite></p> + +<p>“Mr. Hill is decidedly doctrinaire, but his book is packed with +scientific and sociological facts, and it gives the reader healthy +intellectual exercise.”—<cite>Christian World.</cite></p> + +<p>“Shows wide reading, is written in a forcible and clear style, and +contains much that is interesting, fresh, and acute.”—<cite>Aberdeen +Free Press.</cite></p> + +<p>“It is a book of equal calibre with Mr. Kidd’s and goes even +deeper than that remarkable production into the springs of life and +conduct.”—<cite>Methodist Recorder.</cite></p> + +<p>“This most suggestive and valuable work, which contains abundant +sociological data.”—<cite>Aberdeen Journal.</cite></p> + +<p>“Mr. George Chatterton Hill has written a volume of surpassing +interest not alone to scientific but to theological students.”—<cite>Catholic +Times.</cite></p> + +<hr /> +<p class="tac"><span class="smcap">Published by</span> A. & C. BLACK, SOHO SQUARE, LONDON, W.<br /><br /><br /></p></div> + +<p><span class="pagenum hide" title="332"><a name="Page_332" id="Page_332"></a></span></p> + + + +<hr class="chap" /> + +<h2>RUDOLF EUCKEN’S<br /> +PHILOSOPHY OF LIFE</h2> + +<p class="tac fs65 pt12b02em">BY</p> + +<p class="tac fs120">W. R. BOYCE GIBSON</p> + +<p class="tac fs65">LECTURER IN PHILOSOPHY IN THE UNIVERSITY OF LONDON</p> + +<p class="tac fs85 pt12b02em">SECOND EDITION</p> + +<p class="tac">Crown 8vo, Cloth, with Frontispiece Portrait of Rudolf Eucken.</p> + +<p class="tac">Price <b><span class="fs120">3s. 6d.</span></b> net.</p> + +<p class="tac"><i>Post Free, Price</i> <b><span class="fs120">3s. 10d.</span></b></p> + +<p class="tac pt12b02em">SOME PRESS OPINIONS</p> + +<div class="fs85 mlr10em"> +<p>“Mr. Gibson has given us in small compass a lucid exposition of the +philosophical system of Eucken, who is Professor of Philosophy in Jena. . . . +This is a most suggestive and stimulating book. In a very real +sense it has brought philosophy down to earth and is deserving of +serious study.”—<cite>Aberdeen Free Press.</cite></p> + +<p>“To it the interested reader will turn with expectation, and his +expectation is likely to be more than realised. For Dr. Boyce Gibson +is himself a scholar, as well as an enthusiastic lover of this great +scholar.”—<cite>Expository Times.</cite></p> + +<p>“No reader should fail to find pleasure in a book so full of fresh +and stimulating thought, expressed with great felicity of language.”—<cite>The +Scottish Review.</cite></p> + +<p>“It is done with just the proper combination of sympathy and +criticism.”—<cite>British Weekly.</cite></p> + +<p>“This little book on Eucken’s Philosophy is of quite exceptional +interest and importance.”—<cite>The Inquirer.</cite></p> + +<p>“Professor Boyce Gibson . . . has performed a real service in +promoting the acquaintance of English, and American students with a +thinker whose distinctive views give him a special claim to their +attention. . . . Professor Gibson has achieved a notable success, +writing briefly, lucidly, and sympathetically.”—<cite>The New Age.</cite></p> + +<hr /> +<p class="tac"><span class="smcap">Published by</span> A. & C. BLACK, SOHO SQUARE, LONDON, W.<br /><br /><br /></p></div> + +<hr class="chap" /> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"> + +<p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">1</span></a> Windelband (<cite lang="de" xml:lang="de">Geschichte und Naturwissenschaft</cite>, 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">2</span></a> See J. Arth. Thomson, <cite>The Science of Life</cite>, London, 1899.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">3</span></a> E. B. Wilson, <cite>The Cell in Development and Inheritance</cite>, New York, +Macmillan, 1896.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_4_4" id="Footnote_4_4"></a><a href="#FNanchor_4_4"><span class="label">4</span></a> <cite>Amer. Journ. Physiol.</cite> vols. iii. and iv. 1900.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">5</span></a> According to Delage (<cite>Arch. Zool. exp.</cite>, 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_6_6" id="Footnote_6_6"></a><a href="#FNanchor_6_6"><span class="label">6</span></a> The older theories, attributing to fertilisation (or to “conjugation,” <i>i.e.</i> +its equivalent in Protozoa), some sort of “renovation” or “rejuvenescence” +of the race, have been almost completely given up. (See Calkins, <cite lang="de" xml:lang="de">Arch. für +Entwickelungsmechanik</cite>, 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!</p></div> + +<div class="footnote"> + +<p><a name="Footnote_7_7" id="Footnote_7_7"></a><a href="#FNanchor_7_7"><span class="label">7</span></a> The phrase “<i lang="la" xml:lang="la">ceteris paribus</i>” 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_8_8" id="Footnote_8_8"></a><a href="#FNanchor_8_8"><span class="label">8</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_9_9" id="Footnote_9_9"></a><a href="#FNanchor_9_9"><span class="label">9</span></a> <cite lang="de" xml:lang="de">Das Keimplasma</cite>, Jena, 1892.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_10_10" id="Footnote_10_10"></a><a href="#FNanchor_10_10"><span class="label">10</span></a> <cite lang="de" xml:lang="de">Die Bedeutung der Kernteilungsfiguren</cite>, Leipzig, 1883.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_11_11" id="Footnote_11_11"></a><a href="#FNanchor_11_11"><span class="label">11</span></a> <cite lang="de" xml:lang="de">Unsere Körperform</cite>, Leipzig, 1875.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_12_12" id="Footnote_12_12"></a><a href="#FNanchor_12_12"><span class="label">12</span></a> <cite lang="de" xml:lang="de">Die Entwickelungsgeschichte der Unke</cite>, Leipzig, 1875.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_13_13" id="Footnote_13_13"></a><a href="#FNanchor_13_13"><span class="label">13</span></a> <cite lang="de" xml:lang="de">Gesammelte Abhandlungen</cite>, Leipzig, 1895. Most important theoretical +papers:—<cite lang="de" xml:lang="de">Zeitschr. Biolog.</cite> 21, 1885; <cite lang="de" xml:lang="de">Die Entwickelungsmechanik der Organismen</cite>, +Wien, 1890; <cite lang="de" xml:lang="de">Vorträge und Aufsätze über Entwickelungsmechanik</cite>, +Heft i., Leipzig, 1905.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_14_14" id="Footnote_14_14"></a><a href="#FNanchor_14_14"><span class="label">14</span></a> <i>Virchow’s Archiv.</i> 114, 1888.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_15_15" id="Footnote_15_15"></a><a href="#FNanchor_15_15"><span class="label">15</span></a> <cite lang="de" xml:lang="de">Zeitschr. wiss. Zool.</cite> 53, 1891.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_16_16" id="Footnote_16_16"></a><a href="#FNanchor_16_16"><span class="label">16</span></a> <cite lang="de" xml:lang="de">Zeitschr. wiss. Zool.</cite> 55, 1892.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_17_17" id="Footnote_17_17"></a><a href="#FNanchor_17_17"><span class="label">17</span></a> In the pressure experiments I had altered the relative position of the +nuclei <i lang="la" xml:lang="la">in origine</i>. 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 <a href="#Page_73">73</a>)—it must suffice here to have mentioned them. (For further information +see my paper in <cite lang="de" xml:lang="de">Archiv. f. Entwickelungsmechanik</cite>, xiv., 1902, page 500.)</p></div> + +<div class="footnote"> + +<p><a name="Footnote_18_18" id="Footnote_18_18"></a><a href="#FNanchor_18_18"><span class="label">18</span></a> <i>Mitteil. Neapel. 11, 1893.</i></p></div> + +<div class="footnote"> + +<p><a name="Footnote_19_19" id="Footnote_19_19"></a><a href="#FNanchor_19_19"><span class="label">19</span></a> But the elementary magnets would have to be bilateral!</p></div> + +<div class="footnote"> + +<p><a name="Footnote_20_20" id="Footnote_20_20"></a><a href="#FNanchor_20_20"><span class="label">20</span></a> <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 2, 1895.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_21_21" id="Footnote_21_21"></a><a href="#FNanchor_21_21"><span class="label">21</span></a> <cite lang="de" xml:lang="de">Anat. Anz.</cite> 10, 1895.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_22_22" id="Footnote_22_22"></a><a href="#FNanchor_22_22"><span class="label">22</span></a> <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 3, 1896.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_23_23" id="Footnote_23_23"></a><a href="#FNanchor_23_23"><span class="label">23</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_24_24" id="Footnote_24_24"></a><a href="#FNanchor_24_24"><span class="label">24</span></a> Compare my <cite lang="de" xml:lang="de">Analytische Theorie der organischen Entwickelung</cite>, Leipzig, +1894, and my reviews in <cite lang="de" xml:lang="de">Ergebnisse der Anatomie und Entwickelungsgeschichte</cite>, +vols. viii. xi. xiv., 1899–1905. A shorter review is given in +<cite lang="de" xml:lang="de">Ergebnisse der Physiologie</cite>, vol. v., 1906. The full literature will be found +in these reviews.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_25_25" id="Footnote_25_25"></a><a href="#FNanchor_25_25"><span class="label">25</span></a> 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 <a href="#Page_65">65</a>, note <a href="#Footnote_17_17">17</a>.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_26_26" id="Footnote_26_26"></a><a href="#FNanchor_26_26"><span class="label">26</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_27_27" id="Footnote_27_27"></a><a href="#FNanchor_27_27"><span class="label">27</span></a> The reader will remember (see page <a href="#Page_65">65</a>, note <a href="#Footnote_17_17">17</a>), 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_28_28" id="Footnote_28_28"></a><a href="#FNanchor_28_28"><span class="label">28</span></a> <cite>Journ. Exp. Zool.</cite> 1, 1904.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_29_29" id="Footnote_29_29"></a><a href="#FNanchor_29_29"><span class="label">29</span></a> 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, <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 23, 1907). +The final decision always depends on experiment.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_30_30" id="Footnote_30_30"></a><a href="#FNanchor_30_30"><span class="label">30</span></a> 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, <cite lang="de" xml:lang="de">Archiv f. Entwickelungsmechanik</cite>, +7, p. 98; and Brachet, <i lang="la" xml:lang="la">ibid.</i> 22, p. 325.)</p></div> + +<div class="footnote"> + +<p><a name="Footnote_31_31" id="Footnote_31_31"></a><a href="#FNanchor_31_31"><span class="label">31</span></a> <cite lang="de" xml:lang="de">Studien über Protoplasmamechanik</cite>, Leipzig, 1886.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_32_32" id="Footnote_32_32"></a><a href="#FNanchor_32_32"><span class="label">32</span></a> <cite lang="de" xml:lang="de">Unters. üb. mikroskopische Schäume und das Protoplasma</cite>, Leipzig, 1892.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_33_33" id="Footnote_33_33"></a><a href="#FNanchor_33_33"><span class="label">33</span></a> <cite lang="de" xml:lang="de">Jena. Zeitschr.</cite> 26, 1892.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_34_34" id="Footnote_34_34"></a><a href="#FNanchor_34_34"><span class="label">34</span></a> According to Zur Strassen’s results the early embryology of <i class="biological-name">Ascaris</i> +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 <i class="biological-name">Ascaris</i> stands quite apart and presents a great +number of unsolved problems; unfortunately, the germ of this form has not +been accessible to experiment hitherto.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_35_35" id="Footnote_35_35"></a><a href="#FNanchor_35_35"><span class="label">35</span></a> 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,” <i>Ergeb. Anat. u. Entw.-gesch.</i> 15, 1906). This <em>very pessimistic</em> survey +is the more valuable as it is written by a convinced “mechanist.”</p></div> + +<div class="footnote"> + +<p><a name="Footnote_36_36" id="Footnote_36_36"></a><a href="#FNanchor_36_36"><span class="label">36</span></a> Compare the analytical discussions of Klebs, to whom we owe a great +series of important discoveries in the field of morphogenetic “means” in +botany. (<cite lang="de" xml:lang="de">Willkürliche Entwickelungsänderungen bei Pflanzen</cite>, Jena, 1903; +see also <cite lang="de" xml:lang="de">Biol. Centralblatt</cite>, vol. xxiv., 1904, and my reply to Klebs, <i lang="la" xml:lang="la">ibid.</i> 23, 1903.)</p></div> + +<div class="footnote"> + +<p><a name="Footnote_37_37" id="Footnote_37_37"></a><a href="#FNanchor_37_37"><span class="label">37</span></a> <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 17, 1904.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_38_38" id="Footnote_38_38"></a><a href="#FNanchor_38_38"><span class="label">38</span></a> <cite lang="de" xml:lang="de">Zeitschr. wiss. Zool.</cite> 55, 1902; and <cite lang="de" xml:lang="de">Mitt. Neapel.</cite> 11, 1903.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_39_39" id="Footnote_39_39"></a><a href="#FNanchor_39_39"><span class="label">39</span></a> In certain cases part of the specific feature of the process in question may +also depend on the “cause” which is localising it, <i>e.g.</i> in the galls of plants.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_40_40" id="Footnote_40_40"></a><a href="#FNanchor_40_40"><span class="label">40</span></a> Herbst, “Ueber die Bedeutung die Reizphysiologie für die kausale +Auffassung von Vorgängen in der tierischen Ontogenese” (<cite lang="de" xml:lang="de">Biol. Centralblatt</cite>, +vols. xiv., 1894, and xv., 1895); <cite lang="de" xml:lang="de">Formative Reize in der tierischen Ontogenese</cite>, +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 <cite lang="de" xml:lang="de">Ergebnisse der Anatomie und Entwickelungsgeschichte</cite>, +vols. xi. and xiv., 1902 and 1905.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_41_41" id="Footnote_41_41"></a><a href="#FNanchor_41_41"><span class="label">41</span></a> Compare the important papers by J. Loeb, <cite lang="de" xml:lang="de">Untersuchungen zur +physiologischen Morphologie der Tiere</cite>, Würzburg, 1891–2.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_42_42" id="Footnote_42_42"></a><a href="#FNanchor_42_42"><span class="label">42</span></a> 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).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_43_43" id="Footnote_43_43"></a><a href="#FNanchor_43_43"><span class="label">43</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_44_44" id="Footnote_44_44"></a><a href="#FNanchor_44_44"><span class="label">44</span></a> A full account of the present state of the subject will be found in +Morgan’s <cite>Experimental Zoology</cite>, New York, 1907.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_45_45" id="Footnote_45_45"></a><a href="#FNanchor_45_45"><span class="label">45</span></a> 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, <i>Pflüger’s Arch.</i> +93, 1902.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_46_46" id="Footnote_46_46"></a><a href="#FNanchor_46_46"><span class="label">46</span></a> It seems that in some cases (<i class="biological-name">Dinophilus</i>, certain Arthropods) the sexual +products are invariably determined as “arrenogennetic” or as “thelygennetic” +(Wilson, <cite>Journ. Exp. Zool.</cite> 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, <cite lang="de" xml:lang="de">Verh. D. Zool. Ges.</cite> 1905–7).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_47_47" id="Footnote_47_47"></a><a href="#FNanchor_47_47"><span class="label">47</span></a> Driesch, <cite lang="de" xml:lang="de">Die organischen Regulationen</cite>, Leipzig, 1901; Morgan, <cite>Regeneration</cite>, +New York, 1901.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_48_48" id="Footnote_48_48"></a><a href="#FNanchor_48_48"><span class="label">48</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_49_49" id="Footnote_49_49"></a><a href="#FNanchor_49_49"><span class="label">49</span></a> 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).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_50_50" id="Footnote_50_50"></a><a href="#FNanchor_50_50"><span class="label">50</span></a> 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 <em>whole</em> these single “formative stimuli” +might properly be said to belong to its “internal means”—in the widest +sense of the word.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_51_51" id="Footnote_51_51"></a><a href="#FNanchor_51_51"><span class="label">51</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_52_52" id="Footnote_52_52"></a><a href="#FNanchor_52_52"><span class="label">52</span></a> I merely mention here the still “simpler” one—applicable of course +to regeneration proper exclusively—that for the simple reason of being +“wounded,” <i>i.e.</i> being a surface open to the medium, the “wound” brings +forth all that is necessary to complete the organism.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_53_53" id="Footnote_53_53"></a><a href="#FNanchor_53_53"><span class="label">53</span></a> 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. (<cite lang="de" xml:lang="de">Arch. Entw. +Mech.</cite> 1, 1894, p. 69.)</p></div> + +<div class="footnote"> + +<p><a name="Footnote_54_54" id="Footnote_54_54"></a><a href="#FNanchor_54_54"><span class="label">54</span></a> 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, <cite>Journ. exp. Zool.</cite> 2, 1905).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_55_55" id="Footnote_55_55"></a><a href="#FNanchor_55_55"><span class="label">55</span></a> For a good discussion of “super-regeneration” in the roots of plants see +Němec, <cite lang="de" xml:lang="de">Studien über die Regeneration</cite>, 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.). (<cite lang="de" xml:lang="de">Biol. Centralbl.</cite> 22, 1902, p. 385; <cite lang="de" xml:lang="de">Ber. +Bot. Ges.</cite> 20, 1902, p. 81.) A fine experiment is due to Miehe. The alga +<i class="biological-name">Cladophora</i> 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. (<cite lang="de" xml:lang="de">Ber. Bot. Ges.</cite> 23, 1905, p. 257.) For fuller analysis of all +the problems of this chapter see my Organische Regulationen, my reviews +in the <cite lang="de" xml:lang="de">Ergebnisse der Anatomie und Entwickelungsgeschichte</cite>, vols. viii. xi. +xiv., and my Boston address mentioned above. Compare also Fitting, +<cite lang="de" xml:lang="de">Ergebn. d. Physiol.</cite> vols. iv. and v.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_56_56" id="Footnote_56_56"></a><a href="#FNanchor_56_56"><span class="label">56</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_57_57" id="Footnote_57_57"></a><a href="#FNanchor_57_57"><span class="label">57</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_58_58" id="Footnote_58_58"></a><a href="#FNanchor_58_58"><span class="label">58</span></a> The distance of the other boundary line from <i>a</i> or <i>b</i> would be given by +the value of <i>s</i>.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_59_59" id="Footnote_59_59"></a><a href="#FNanchor_59_59"><span class="label">59</span></a> A far more thorough analysis of this differentiation has been attempted +in my paper, “Die Localisation morphogenetischer Vorgänge. Ein Beweis +vitalistischen Geschehens,” Leipzig, 1899.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_60_60" id="Footnote_60_60"></a><a href="#FNanchor_60_60"><span class="label">60</span></a> This statement is <em>not strictly</em> correct for <i class="biological-name">Tubularia</i>. I found (<cite lang="de" xml:lang="de">Archiv f. +Entwickelungsmechanik</cite>, 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.”</p></div> + +<div class="footnote"> + +<p><a name="Footnote_61_61" id="Footnote_61_61"></a><a href="#FNanchor_61_61"><span class="label">61</span></a> One might object here that in a piece of a <i class="biological-name">Tubularia</i> 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 <em>absolute size</em> 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 +<em>independent</em> way. These would never result in any “harmonious,” any +proportionate structure, but a structure of the “normal” proportionality +<em>and size</em> at its two ends and non-existent in the middle!</p></div> + +<div class="footnote"> + +<p><a name="Footnote_62_62" id="Footnote_62_62"></a><a href="#FNanchor_62_62"><span class="label">62</span></a> See my article in <cite lang="de" xml:lang="de">Biolog. Centralblatt</cite>, 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 <i class="biological-name">Clavellina</i> could be transformed, by chemical processes exclusively, into +a system of which only a certain <em>part</em> consists of that substance of which +the starting-point had been composed in its <em>completeness</em>.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_63_63" id="Footnote_63_63"></a><a href="#FNanchor_63_63"><span class="label">63</span></a> Besides the specified poles determined by the polar-bilateral structure +of the protoplasm.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_64_64" id="Footnote_64_64"></a><a href="#FNanchor_64_64"><span class="label">64</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_65_65" id="Footnote_65_65"></a><a href="#FNanchor_65_65"><span class="label">65</span></a> My “first proof of vitalism” was first developed in the paper, “Die +Localisation morphogenetischer Vorgänge,” Leipzig, 1899. (See additional +remarks in <cite lang="de" xml:lang="de">Organische Regulationem</cite>, Leipzig, 1901, and in <cite lang="de" xml:lang="de">Archiv für +Entwickelungsmechanik</cite>, 14, 1902.) I cannot admit that any really serious +objection has been brought forward against it. (See my articles in <cite lang="de" xml:lang="de">Biologisches +Centralblatt</cite>, 22, 23, 27, and in <cite lang="de" xml:lang="de">Ergebnisse d. Anat. u. Entwickelungsgesch</cite>. +11, 14.) An historical sketch of vitalism will be found in my book, <cite lang="de" xml:lang="de">Der +Vitalismus als Geschichte und als Lehre</cite>, Leipzig, 1905.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_66_66" id="Footnote_66_66"></a><a href="#FNanchor_66_66"><span class="label">66</span></a> 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.)</p></div> + +<div class="footnote"> + +<p><a name="Footnote_67_67" id="Footnote_67_67"></a><a href="#FNanchor_67_67"><span class="label">67</span></a> 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 <a href="#Page_65">65</a> note <a href="#Footnote_17_17">17</a>, and page <a href="#Page_73">73</a>.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_68_68" id="Footnote_68_68"></a><a href="#FNanchor_68_68"><span class="label">68</span></a> 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. <a href="#Page_109">109</a>). 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_69_69" id="Footnote_69_69"></a><a href="#FNanchor_69_69"><span class="label">69</span></a> <cite lang="de" xml:lang="de">Biol. Centralblatt.</cite> 23, 1903.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_70_70" id="Footnote_70_70"></a><a href="#FNanchor_70_70"><span class="label">70</span></a> Certain phenomena of the physiology of growth of <i class="biological-name">Geranium Robertianum</i>, +recently discussed by Francé from a vitalistic point of view (<cite lang="de" xml:lang="de">Zeitschr. Entw. +lehre</cite>. 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_71_71" id="Footnote_71_71"></a><a href="#FNanchor_71_71"><span class="label">71</span></a> Driesch, <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 5, 1897.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_72_72" id="Footnote_72_72"></a><a href="#FNanchor_72_72"><span class="label">72</span></a> Driesch, <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 14, 1902.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_73_73" id="Footnote_73_73"></a><a href="#FNanchor_73_73"><span class="label">73</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_74_74" id="Footnote_74_74"></a><a href="#FNanchor_74_74"><span class="label">74</span></a> “Retro”-differentiation, of course, is not “Re”-differentiation (“Umdifferenzierung,” +see p. <a href="#Page_111">111</a>), though it may help it to occur.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_75_75" id="Footnote_75_75"></a><a href="#FNanchor_75_75"><span class="label">75</span></a> Of course such a real decay of parts may happen in other cases.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_76_76" id="Footnote_76_76"></a><a href="#FNanchor_76_76"><span class="label">76</span></a> Certain cases of retro-differentiation occurring under conditions of strict +fasting will be described in a later chapter.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_77_77" id="Footnote_77_77"></a><a href="#FNanchor_77_77"><span class="label">77</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_78_78" id="Footnote_78_78"></a><a href="#FNanchor_78_78"><span class="label">78</span></a> Compare Herbst, <cite lang="de" xml:lang="de">Biol. Centralbl.</cite> 15, 1895; and Detto, <cite lang="de" xml:lang="de">Die Theorie der +direkten Anpassung</cite>, Jena, 1904. A full account of the literature will be +found in these papers.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_79_79" id="Footnote_79_79"></a><a href="#FNanchor_79_79"><span class="label">79</span></a> Vöchting (<cite lang="de" xml:lang="de">Jahrb. wiss. Bot.</cite> 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 +<cite lang="de" xml:lang="de">Organische Regulationen</cite>, 1901, p. 84.) A true and simple instance of a +“secondary adaptation” seems to be furnished in a case described by +Boirivant. In <i class="biological-name">Robinia</i> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_80_80" id="Footnote_80_80"></a><a href="#FNanchor_80_80"><span class="label">80</span></a> <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 17, 1904.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_81_81" id="Footnote_81_81"></a><a href="#FNanchor_81_81"><span class="label">81</span></a> Roux, <cite lang="de" xml:lang="de">Gesammelte Abhandlungen</cite>, vol. i. 1895; in particular, <cite lang="de" xml:lang="de">Der Kampf +der Teile im Organismus</cite>, Leipzig, 1881.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_82_82" id="Footnote_82_82"></a><a href="#FNanchor_82_82"><span class="label">82</span></a> <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 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.)</p></div> + +<div class="footnote"> + +<p><a name="Footnote_83_83" id="Footnote_83_83"></a><a href="#FNanchor_83_83"><span class="label">83</span></a> Atrophy of muscles by inactivity is not to be confused with atrophy by +cutting the motor nerve; the latter is very much more complete.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_84_84" id="Footnote_84_84"></a><a href="#FNanchor_84_84"><span class="label">84</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_85_85" id="Footnote_85_85"></a><a href="#FNanchor_85_85"><span class="label">85</span></a> What has been really <em>proved</em> 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, <cite>Journ. exp. Zool.</cite> 3, 1906, where Child has given a summary of +his theory.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_86_86" id="Footnote_86_86"></a><a href="#FNanchor_86_86"><span class="label">86</span></a> Even in Vöchting’s experiments (see page <a href="#Page_174">174</a>, note <a href="#Footnote_79_79">79</a>), 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 <a href="#Page_113">113</a>). 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_87_87" id="Footnote_87_87"></a><a href="#FNanchor_87_87"><span class="label">87</span></a> <cite lang="de" xml:lang="de">Beiträge zur Lehre von den Functionen der Nervencentren des Frosches</cite>, +Berlin, 1869.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_88_88" id="Footnote_88_88"></a><a href="#FNanchor_88_88"><span class="label">88</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_89_89" id="Footnote_89_89"></a><a href="#FNanchor_89_89"><span class="label">89</span></a> General literature: Fröhlich, <cite lang="de" xml:lang="de">Das natürliche Zweckmüssigkeitsprincip +in seiner Bedeutung für Krankheit und Heilung</cite>, 1894. Driesch, <cite lang="de" xml:lang="de">Die +organischen Regulationen</cite>, 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,” <cite lang="de" xml:lang="de">Annal. d. Naturphil.</cite> 5, 1906. Among the +general text-books of physiology those by Pfeffer (<cite lang="de" xml:lang="de">Pflanzenphysiologie</cite>, 1897–1904) +and von Bunge (<cite lang="de" xml:lang="de">Lehrbuch d. Phys. d. Menschen</cite>, 1901) are the fullest on +the subject of “regulations.” See also different papers on general pathology +by Ribbert.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_90_90" id="Footnote_90_90"></a><a href="#FNanchor_90_90"><span class="label">90</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_91_91" id="Footnote_91_91"></a><a href="#FNanchor_91_91"><span class="label">91</span></a> 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. +</p> +<p> +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, <cite lang="de" xml:lang="de">Arch. f. Entw. +Mech.</cite> 2, p. 227). “Acclimatisation” does not allow of a sharp general definition; +it may be the result of very <em>different</em> kinds of adaptations in our sense +of the word.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_92_92" id="Footnote_92_92"></a><a href="#FNanchor_92_92"><span class="label">92</span></a> 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 <i class="biological-name">Mimosa</i> +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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_93_93" id="Footnote_93_93"></a><a href="#FNanchor_93_93"><span class="label">93</span></a> Rubner, <cite lang="de" xml:lang="de">Die Gesetze des Energieverbrauches bei der Ernährung</cite>, Leipzig +u. Wein, 1902.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_94_94" id="Footnote_94_94"></a><a href="#FNanchor_94_94"><span class="label">94</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_95_95" id="Footnote_95_95"></a><a href="#FNanchor_95_95"><span class="label">95</span></a> <cite lang="de" xml:lang="de">Jahrb. wiss. Bot.</cite> 36, 1901.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_96_96" id="Footnote_96_96"></a><a href="#FNanchor_96_96"><span class="label">96</span></a> 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 (<cite lang="fr" xml:lang="fr">C. rend. Soc. Biol.</cite> 53, 1901, p. 880).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_97_97" id="Footnote_97_97"></a><a href="#FNanchor_97_97"><span class="label">97</span></a> In the different experiments of Nathansohn (<cite lang="de" xml:lang="de">Jahrb. wiss. Bot.</cite> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_98_98" id="Footnote_98_98"></a><a href="#FNanchor_98_98"><span class="label">98</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_99_99" id="Footnote_99_99"></a><a href="#FNanchor_99_99"><span class="label">99</span></a> See Stahl, <cite lang="de" xml:lang="de">Naturw. Wochenschrift</cite>, N. F. 5, 1906, No. 19.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_100_100" id="Footnote_100_100"></a><a href="#FNanchor_100_100"><span class="label">100</span></a> <cite>Arch. Anat. Phys.</cite>, Phys. Abt. Suppl., 1902.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_101_101" id="Footnote_101_101"></a><a href="#FNanchor_101_101"><span class="label">101</span></a> 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, <cite>Phil. Trans. London</cite>, 178 B, 1888; Merrifield, <cite>Trans. Ent. Soc. +London</cite>, 1898). The same holds for chromatic adaptations in crabs (Gamble +and Keeble, <cite>Quart. Journ. Micr. Sci.</cite> 43, 1900; Minkiewicz, <cite>Arch. Zool. exp. +et gén.</cite> sér. 4, 7, notes, 1907).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_102_102" id="Footnote_102_102"></a><a href="#FNanchor_102_102"><span class="label">102</span></a> The theory of oxidation we have shortly sketched here was developed +in chapter B. 5, of my <cite lang="de" xml:lang="de">Organische Regulationen</cite>. Recent discoveries of +Winterstein’s (<cite lang="de" xml:lang="de">Zeitschr. allg. Physiol.</cite> 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.”</p></div> + +<div class="footnote"> + +<p><a name="Footnote_103_103" id="Footnote_103_103"></a><a href="#FNanchor_103_103"><span class="label">103</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_104_104" id="Footnote_104_104"></a><a href="#FNanchor_104_104"><span class="label">104</span></a> <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 18, 1904.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_105_105" id="Footnote_105_105"></a><a href="#FNanchor_105_105"><span class="label">105</span></a> 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 <i lang="fr" xml:lang="fr">sécrétion interne</i> +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 <i class="biological-name">Planaria</i> and infusorians.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_106_106" id="Footnote_106_106"></a><a href="#FNanchor_106_106"><span class="label">106</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_107_107" id="Footnote_107_107"></a><a href="#FNanchor_107_107"><span class="label">107</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_108_108" id="Footnote_108_108"></a><a href="#FNanchor_108_108"><span class="label">108</span></a> Compare the excellent review of the subject by Bayliss and Starling in +the <cite lang="de" xml:lang="de">Ergebnisse der Physiologie</cite>, 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_109_109" id="Footnote_109_109"></a><a href="#FNanchor_109_109"><span class="label">109</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_110_110" id="Footnote_110_110"></a><a href="#FNanchor_110_110"><span class="label">110</span></a> A good review is given by E. Fromm, <cite lang="de" xml:lang="de">Die chemischen Schutzmittel des +Tierkörpers bei Vergiftungen</cite>, Strassburg, 1903.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_111_111" id="Footnote_111_111"></a><a href="#FNanchor_111_111"><span class="label">111</span></a> Davenport, <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 2, 1895–1896, and Hausmann, <i>Pflüger’s +Arch.</i> 113, 1906.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_112_112" id="Footnote_112_112"></a><a href="#FNanchor_112_112"><span class="label">112</span></a> <i>Leçons sur la pathologie comparée de l’inflammation</i>, Paris, 1902.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_113_113" id="Footnote_113_113"></a><a href="#FNanchor_113_113"><span class="label">113</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_114_114" id="Footnote_114_114"></a><a href="#FNanchor_114_114"><span class="label">114</span></a> See Jacoby, <cite lang="de" xml:lang="de">Immunität und Disposition</cite>, Wiesbaden, 1906.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_115_115" id="Footnote_115_115"></a><a href="#FNanchor_115_115"><span class="label">115</span></a> <cite>Collected Studies on Immunity by Ehrlich and his Collaborators</cite>, translated +by Ch. Bolduan, New York and London, 1906.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_116_116" id="Footnote_116_116"></a><a href="#FNanchor_116_116"><span class="label">116</span></a> 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, <cite>Biol. Bull.</cite> +9, 1905.)</p></div> + +<div class="footnote"> + +<p><a name="Footnote_117_117" id="Footnote_117_117"></a><a href="#FNanchor_117_117"><span class="label">117</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_118_118" id="Footnote_118_118"></a><a href="#FNanchor_118_118"><span class="label">118</span></a> Here again I should like to except from this statement the discoveries +of Pawlow. See page <a href="#Page_204">204</a>, note <a href="#Footnote_108_108">108</a>.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_119_119" id="Footnote_119_119"></a><a href="#FNanchor_119_119"><span class="label">119</span></a> 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 (<cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 5, 1897). The same is true, it seems to me, +with regard to certain recent discoveries made by R. Pearl on <i class="biological-name">Ceratophyllum</i> +(<cite>Carnegie Inst. Wash. Publ.</cite> No. 58, 1907); and by Zeleny on a medusa +(<cite>Journ. exp. Zool.</cite> 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, <cite lang="de" xml:lang="de">Ergeb. +Physiol.</cite> 5, 1906, p. 682).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_120_120" id="Footnote_120_120"></a><a href="#FNanchor_120_120"><span class="label">120</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_121_121" id="Footnote_121_121"></a><a href="#FNanchor_121_121"><span class="label">121</span></a> <cite lang="de" xml:lang="de">Ueber das Gedächtnis als eine allgemeine Function der organischen +Materie</cite>, Wien, 1870. New edition in <cite lang="de" xml:lang="de">Klassiker d. exakt. Wiss.</cite>, Leipzig, +Engelmann.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_122_122" id="Footnote_122_122"></a><a href="#FNanchor_122_122"><span class="label">122</span></a> <cite lang="de" xml:lang="de">Die Mneme</cite>, Leipzig, 1904.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_123_123" id="Footnote_123_123"></a><a href="#FNanchor_123_123"><span class="label">123</span></a> Driesch, <cite lang="de" xml:lang="de">Organ. Regul.</cite> 1901.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_124_124" id="Footnote_124_124"></a><a href="#FNanchor_124_124"><span class="label">124</span></a> The “ideal whole” is also proved to exist, if any <em>given</em> “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 <a href="#Page_112">112</a>, note <a href="#Footnote_48_48">48</a>, and my <cite lang="de" xml:lang="de">Organ. Regul.</cite> pp. 77, 78.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_125_125" id="Footnote_125_125"></a><a href="#FNanchor_125_125"><span class="label">125</span></a> 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.”</p></div> + +<div class="footnote"> + +<p><a name="Footnote_126_126" id="Footnote_126_126"></a><a href="#FNanchor_126_126"><span class="label">126</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_127_127" id="Footnote_127_127"></a><a href="#FNanchor_127_127"><span class="label">127</span></a> A full “analytical theory of regeneration” has been developed elsewhere +(<cite lang="de" xml:lang="de">Organ. Regul.</cite> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_128_128" id="Footnote_128_128"></a><a href="#FNanchor_128_128"><span class="label">128</span></a> 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.”</p></div> + +<div class="footnote"> + +<p><a name="Footnote_129_129" id="Footnote_129_129"></a><a href="#FNanchor_129_129"><span class="label">129</span></a> New edition in the “Klassiker d. exakt. Wiss.” Leipzig, Engelmann; +see also Bateson, <i>Mendel’s Principles of Heredity</i>, Cambridge, 1902.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_130_130" id="Footnote_130_130"></a><a href="#FNanchor_130_130"><span class="label">130</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_131_131" id="Footnote_131_131"></a><a href="#FNanchor_131_131"><span class="label">131</span></a> 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 <cite>Experimental Zoology</cite>, New York, 1907, +a full account of the whole matter is given.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_132_132" id="Footnote_132_132"></a><a href="#FNanchor_132_132"><span class="label">132</span></a> <cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 21, 22, and 24, 1906–7; see also Doncaster, <cite>Phil. Trans. +Royal Soc.</cite> 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 +<em>as such</em>, at least with regard to certain features of its organisation.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_133_133" id="Footnote_133_133"></a><a href="#FNanchor_133_133"><span class="label">133</span></a> Only the nucleus of the egg had entered its first stages of activity.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_134_134" id="Footnote_134_134"></a><a href="#FNanchor_134_134"><span class="label">134</span></a> The first proof of vitalism, indeed, rests upon the analysis of the +differentiation of an harmonious-equipotential system as a <em>whole</em>: this <em>whole</em> +cannot be a machine that would relate to differentiation as a <em>whole</em>; the +question whether there might be any machines distributed <em>in</em> the whole, in +the form of the nuclei is of no importance at all in this argument. Moreover +the pressure experiments (see page <a href="#Page_63">63</a>) 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 <em>any</em> way.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_135_135" id="Footnote_135_135"></a><a href="#FNanchor_135_135"><span class="label">135</span></a> Boveri tried to fertilise enucleated fragments of the egg of <i class="biological-name">Sphaerechinus</i> +with the sperm of <i class="biological-name">Echinus</i>. He failed to get any results in isolated experiments, +but found a few small larvae of the pure <i class="biological-name">Echinus</i> type in large +cultures consisting of shaken eggs. But later experiments on hybridisation +in sea-urchins have shown that a full hybrid of <i class="biological-name">Echinus</i> and <i class="biological-name">Sphaerechinus</i> +may be purely paternal also.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_136_136" id="Footnote_136_136"></a><a href="#FNanchor_136_136"><span class="label">136</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_137_137" id="Footnote_137_137"></a><a href="#FNanchor_137_137"><span class="label">137</span></a> Boveri (<cite lang="de" xml:lang="de">Ergebn. üb. d. Konstitution etc. des Zellkerns</cite>, Jena, 1904; +and “Zellen-Studien VI.” <cite lang="de" xml:lang="de">Jen. Zeitschr.</cite> 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 <em>means</em> 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 <a href="#Page_107">107</a>, note <a href="#Footnote_46_46">46</a>), that the +morphogenetic singularity of <em>one</em> certain specific chromosome can be said to +be proved.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_138_138" id="Footnote_138_138"></a><a href="#FNanchor_138_138"><span class="label">138</span></a> H. M. Vernon, <cite>Variations in Animals and Plants</cite>, London, 1903.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_139_139" id="Footnote_139_139"></a><a href="#FNanchor_139_139"><span class="label">139</span></a> De Vries, <cite lang="de" xml:lang="de">Die Mutationstheorie</cite>, i., 1901; and Klebs, <cite lang="de" xml:lang="de">Jahrb. wiss. Bot.</cite> +42, 1905.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_140_140" id="Footnote_140_140"></a><a href="#FNanchor_140_140"><span class="label">140</span></a> They would not be “real exceptions” if Klebs (<cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 24, +1907) were right in saying that both variations and mutations owe their +existence to external agents. What is really <em>proved</em> by Klebs is the possibility +of changing the <em>type</em> of a curve of variation and of provoking certain discontinuous +varieties by external means. See also Blaringhem (<cite lang="fr" xml:lang="fr">Comptes rend.</cite> +1905–6, and <cite lang="fr" xml:lang="fr">Soc. de Biol.</cite> 59, 1905), and MacDougal (<i>Rep. Depart. Bot. Res., +5th Year-book Carnegie Inst.</i>, Washington, 129).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_141_141" id="Footnote_141_141"></a><a href="#FNanchor_141_141"><span class="label">141</span></a> H. de Vries, <i>Species and Varieties: their Origin by Mutation</i>, London, +1905. A short review of the “mutation-theory” is given by Francé in +<cite lang="de" xml:lang="de">Zeitschrift f. d. Ausbau d. Entwickelungslehre</cite>, 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_142_142" id="Footnote_142_142"></a><a href="#FNanchor_142_142"><span class="label">142</span></a> 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.).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_143_143" id="Footnote_143_143"></a><a href="#FNanchor_143_143"><span class="label">143</span></a> 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, +(<cite lang="de" xml:lang="de">Ausichten und Gespräche über die individuelle und specifische Gestaltung +in der Natur</cite>) 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.”</p></div> + +<div class="footnote"> + +<p><a name="Footnote_144_144" id="Footnote_144_144"></a><a href="#FNanchor_144_144"><span class="label">144</span></a> It seems to me that my argument gives a broader logical basis to the +theory of descent than does that of G. Wolff (<cite lang="de" xml:lang="de">Die Begründung der +Abstammungslehre</cite>, 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_145_145" id="Footnote_145_145"></a><a href="#FNanchor_145_145"><span class="label">145</span></a> See Wigand, <i>Der Darwinismus und die Naturforschung Newton’s und +Cuvier’s</i>, Braunschweig, 1874–7; Nägeli, <i>Mechanisch-physiologische Theorie +der Abstammungslehre</i>, München, 1884; G. Wolff, <i>Beiträge zur Kritik der +Darwin’schen Lehre</i>, 2nd ed. Leipzig, 1898; etc.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_146_146" id="Footnote_146_146"></a><a href="#FNanchor_146_146"><span class="label">146</span></a> <cite lang="de" xml:lang="de">Darwinismus und Lamarckismus</cite>, München, 1905.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_147_147" id="Footnote_147_147"></a><a href="#FNanchor_147_147"><span class="label">147</span></a> This would not be true, if the varieties of plants produced by Blaringhem, +Klebs, and MacDougal by means of <em>external</em> agents were really +“mutations” (comp. page 238, note 3).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_148_148" id="Footnote_148_148"></a><a href="#FNanchor_148_148"><span class="label">148</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_149_149" id="Footnote_149_149"></a><a href="#FNanchor_149_149"><span class="label">149</span></a> Comp. page 238, note 2.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_150_150" id="Footnote_150_150"></a><a href="#FNanchor_150_150"><span class="label">150</span></a> Certain English authors have applied the term “modification” to all kinds +of organic properties acquired from without, whether they are adapted or not.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_151_151" id="Footnote_151_151"></a><a href="#FNanchor_151_151"><span class="label">151</span></a> Of course the inheritance of specific values from the results of fluctuating +variations, leading to new averages of variability (see p. <a href="#Page_265">265</a>), may also be +understood in this manner, the conditions of nourishment acting upon the +adult and upon its germs equally well.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_152_152" id="Footnote_152_152"></a><a href="#FNanchor_152_152"><span class="label">152</span></a> <cite lang="de" xml:lang="de">Berichte üb. d. Sitzung. d. Ges. f. Bot.</cite>, Hamburg, 1887, 3 Heft.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_153_153" id="Footnote_153_153"></a><a href="#FNanchor_153_153"><span class="label">153</span></a> Quite recently Kammerer (<cite lang="de" xml:lang="de">Arch. Entw. Mech.</cite> 25, 1907, p. 7) has +published very important experiments on the inheritance of “acquired” +modifications with regard to the peculiarities of reproduction in <i class="biological-name">Salamandra +atra</i> and <i class="biological-name">S. maculosa</i>. It seems rather improbable—though not absolutely +impossible—that the germ cells were directly affected by the external +modifying agent in this case.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_154_154" id="Footnote_154_154"></a><a href="#FNanchor_154_154"><span class="label">154</span></a> 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” (<i>see</i> p. <a href="#Page_186">186</a>) +<em>might</em> be due to the inheritance of the results of active immunity as an +adaptation, just as adaptive congenital structures <em>might</em> be due to such +an inheritance.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_155_155" id="Footnote_155_155"></a><a href="#FNanchor_155_155"><span class="label">155</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_156_156" id="Footnote_156_156"></a><a href="#FNanchor_156_156"><span class="label">156</span></a> I repeat once more that we are dealing here with dogmatic “Neo-”Lamarckism +exclusively. This theory indeed claims to explain <em>all</em> 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 <em>all</em> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_157_157" id="Footnote_157_157"></a><a href="#FNanchor_157_157"><span class="label">157</span></a> Compare also the excellent criticism of Lamarckism lately given by +G. Wolff, <cite lang="de" xml:lang="de">Die Begründung der Abstammungslehre</cite>, München, 1907.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_158_158" id="Footnote_158_158"></a><a href="#FNanchor_158_158"><span class="label">158</span></a> 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 <em>taken by itself</em>, it seems to me, would not be +fatal to Neo-Lamarckism in the special form August Pauly gave to this +doctrine.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_159_159" id="Footnote_159_159"></a><a href="#FNanchor_159_159"><span class="label">159</span></a> 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 <em>external</em> means have strengthened +their importance for the general theory of transformism.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_160_160" id="Footnote_160_160"></a><a href="#FNanchor_160_160"><span class="label">160</span></a> 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 <a href="#Page_264">264</a>).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_161_161" id="Footnote_161_161"></a><a href="#FNanchor_161_161"><span class="label">161</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_162_162" id="Footnote_162_162"></a><a href="#FNanchor_162_162"><span class="label">162</span></a> See pp. <a href="#Page_26">26</a>, <a href="#Page_45">45</a>, <a href="#Page_54">54</a>, etc.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_163_163" id="Footnote_163_163"></a><a href="#FNanchor_163_163"><span class="label">163</span></a> An immanent vitalistic phylogeny <em>without</em> a pre-established end has +recently been advocated by H. Bergson (<i>L’évolution créatrice</i>, Paris, 1907).</p></div> + +<div class="footnote"> + +<p><a name="Footnote_164_164" id="Footnote_164_164"></a><a href="#FNanchor_164_164"><span class="label">164</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_165_165" id="Footnote_165_165"></a><a href="#FNanchor_165_165"><span class="label">165</span></a> 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.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_166_166" id="Footnote_166_166"></a><a href="#FNanchor_166_166"><span class="label">166</span></a> <cite lang="de" xml:lang="de">Die Grenzen der naturwissenschaftlichen Begriffsbildung</cite>, Tübingen and +Leipzig, 1902.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_167_167" id="Footnote_167_167"></a><a href="#FNanchor_167_167"><span class="label">167</span></a> The word “universality” to be understood here in quite an unpretentious +quasi-popular meaning, not strictly epistemologically.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_168_168" id="Footnote_168_168"></a><a href="#FNanchor_168_168"><span class="label">168</span></a> To avoid mistakes I wish to say here most emphatically that, according +to Rickert, the method of history is regarded as completely <em>free</em> from subjectivity +as soon as its “values” are once <em>established</em>. But this cannot +avail to save the theory.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_169_169" id="Footnote_169_169"></a><a href="#FNanchor_169_169"><span class="label">169</span></a> 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.</p></div></div> + +<div>*** END OF THE PROJECT GUTENBERG EBOOK 44388 ***</div> +</body> +</html> diff --git a/44388-h/images/fig01.jpg b/44388-h/images/fig01.jpg Binary files differnew file mode 100644 index 0000000..1d3003e --- /dev/null +++ b/44388-h/images/fig01.jpg diff --git a/44388-h/images/fig02.jpg b/44388-h/images/fig02.jpg Binary files differnew file mode 100644 index 0000000..8dc443b --- /dev/null +++ b/44388-h/images/fig02.jpg diff --git a/44388-h/images/fig03.jpg b/44388-h/images/fig03.jpg Binary files differnew file mode 100644 index 0000000..3cd511b --- /dev/null +++ b/44388-h/images/fig03.jpg diff --git a/44388-h/images/fig04.jpg b/44388-h/images/fig04.jpg Binary files differnew file mode 100644 index 0000000..6f6003b --- /dev/null +++ b/44388-h/images/fig04.jpg diff --git a/44388-h/images/fig05.jpg b/44388-h/images/fig05.jpg Binary files differnew file mode 100644 index 0000000..9833ff2 --- /dev/null +++ b/44388-h/images/fig05.jpg diff --git a/44388-h/images/fig06.jpg b/44388-h/images/fig06.jpg Binary files differnew file mode 100644 index 0000000..d959ca4 --- /dev/null +++ b/44388-h/images/fig06.jpg diff --git a/44388-h/images/fig07.jpg b/44388-h/images/fig07.jpg Binary files differnew file mode 100644 index 0000000..df62eff --- /dev/null +++ b/44388-h/images/fig07.jpg diff --git a/44388-h/images/fig08.jpg b/44388-h/images/fig08.jpg Binary files differnew file mode 100644 index 0000000..2823dbe --- /dev/null +++ b/44388-h/images/fig08.jpg diff --git a/44388-h/images/fig09.jpg b/44388-h/images/fig09.jpg Binary files differnew file mode 100644 index 0000000..9c6cf75 --- /dev/null +++ b/44388-h/images/fig09.jpg diff --git a/44388-h/images/fig10.jpg b/44388-h/images/fig10.jpg Binary files differnew file mode 100644 index 0000000..bcfa5e1 --- /dev/null +++ b/44388-h/images/fig10.jpg diff --git a/44388-h/images/fig11.jpg b/44388-h/images/fig11.jpg Binary files differnew file mode 100644 index 0000000..96263f8 --- /dev/null +++ b/44388-h/images/fig11.jpg diff --git a/44388-h/images/fig12.jpg b/44388-h/images/fig12.jpg Binary files differnew file mode 100644 index 0000000..d7a4469 --- /dev/null +++ b/44388-h/images/fig12.jpg diff --git a/44388-h/images/fig13.jpg b/44388-h/images/fig13.jpg Binary files differnew file mode 100644 index 0000000..322df74 --- /dev/null +++ b/44388-h/images/fig13.jpg diff --git a/44388-h/images/fig14.jpg b/44388-h/images/fig14.jpg Binary files differnew file mode 100644 index 0000000..0651886 --- /dev/null +++ b/44388-h/images/fig14.jpg diff --git a/44388-h/images/logo.png b/44388-h/images/logo.png Binary files differnew file mode 100644 index 0000000..3e48335 --- /dev/null +++ b/44388-h/images/logo.png diff --git a/44388-h/images/titlepage.jpg b/44388-h/images/titlepage.jpg Binary files differnew file mode 100644 index 0000000..1bfa61b --- /dev/null +++ b/44388-h/images/titlepage.jpg |
