The Biological Problem of To-day: Preformation Or Epigenesis?

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Oscar Hertwig. The Biological Problem of To-day: Preformation Or Epigenesis?

The Biological Problem of To-day: Preformation Or Epigenesis?

Table of Contents

PREFACE

TRANSLATOR'S INTRODUCTION

THE BIOLOGICAL PROBLEM OF TO-DAY

INTRODUCTION

Footnote

PART I

WEISMANN'S THEORY OF THE GERMPLASM AND DOCTRINE OF DETERMINANTS

Criticism of the Germplasm Theory.[8]

I. Objections to the Hypothesis of Differentiating Division

FIRST GROUP OF FACTS.—UNICELLULAR ORGANISMS

SECOND GROUP OF FACTS.—THE LOWER MULTI-CELLULAR ORGANISMS

THIRD GROUP OF FACTS.—THE PHENOMENA OF REPRODUCTION AND REGENERATION IN PLANTS AND ANIMALS

FOURTH GROUP OF FACTS.—THE PHENOMENA OF HETEROMORPHOSIS.[12]

FIFTH GROUP OF FACTS.—PHENOMENA OF VEGETATIVE AFFINITY.[16]

SUMMARY OF THE CONCLUSIONS IN THE FIRST SECTION

II. ARGUMENTS AGAINST THE DOCTRINE OF DETERMINANTS

Footnote

PART II

THOUGHTS TOWARDS A THEORY OF THE DEVELOPMENT OF ORGANISMS.[17]

Footnote

INDEX AND GLOSSARY

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Oscar Hertwig

The Basis of a Theory of Organic Development

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None the less, who seeks in Wolff's 'Theoria Generationis' an account of the means or forces by which Nature builds up organic forms will seek in vain. The vis essentialis (inherent force) with which Wolff endowed his plastic organic material, or the nisus formativus (formative force), afterwards suggested to science by Blumenbach—what are they but empty words by which men seek to grasp in thought what has eluded them? Wolff's epigenesis was not a complete explanation—indeed, from its fundamental conception it could not possibly be such. For investigation of the natural forces by which development proceeds can advance only slowly and step by step, and for long will constitute the foremost task of biology. The prosecution of biological investigation will continuously endow the theory of epigenesis with a fuller and fuller meaning, but will never transform it into a solution final in the sense of the theory of preformation.

It seems to me that the significance of Wolff's doctrine lies in this: it rejected the purely formal theory of preformation because actual observations were against it. Thereby Wolff freed research from the straitened bonds of prejudice, and entered the only possible path by which science can advance—the path along which the biology of our century has made so great advances.

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