CONTENTS 



CIIAPflR PAGE 



FOREWORD 



I. INTRODUCTION I3 



The development of animal organization — The 

 similarity of all young embryos — The three 

 fundamental layers 



II. THE BEGINNING OF DEVELOPMENT 26 



Egg and sperm — Fertilization, heredity, virgin 

 birth — Development begins 



III. MOVEMENTS AND FOLDINGS 4O 



Formation of the three layers in sea-urchins — 

 Frogs and newts — Lampreys — Birds — Mammals 



IV. THE "organization CENTRE*' 61 



The technique of micro-surgery — The focus 

 around which the embryo is integrated — Birds 

 — Mammals — Sea-urchins — Insects 



V. THE ADDITION OF DETAILS 78 



Secondary organization centres — Special fac- 

 tories making special parts — Mosaic eggs — 

 Different ways of* building up similar struc- 

 tures — Larvae 



VI. THE DEVELOPMENT OF PATTERN 93 



How the organizer works — Particular causes 

 and the general pattern — Regeneration 



VII. THE FINAL ADJUSTMENTS 102 



How embryos are fed — Growth — The influence 

 of function — The nervous system and develop- 

 ment — Hormones — Sex — The activity of genes 

 in development 



INDEX 135 



