Forms of Becoming

Alessandro Minelli is professor of zoology at the University of Padua in Italy. He is the author of "The Development of Animal Form" and the coeditor of "Evolving Pathways: Key Themes in Evolutionary Developmental Biology".

"Minelli provides his distinctive perspective of the field of evolutionary developmental biology. Whether or not readers agree with himon specific points, he raisesmany interesting questions that might well be fuel for long discussions on a summer evening. Overall, this book is stimulating reading and will provide much food for thought."--Christian Peter Klingenberg, Trends in Ecology and Evolution "I enjoyed reading Forms of Becoming. It added depth to my knowledge of the historical background of comparative morphological studies, and it regrounded my appreciation of the diversity of evolutionary modifications in development across animals. I recommend this book as entry-level reading for non-'evo-devo' folks as well as the many developmental and evolutionary biologists whose research involves phenotype. I also recommend this thought-provoking book to graduate students... In summary, Minelli promotes an integrative view that is timely and immensely valuable."--Paula Mabee, BioScience "This book is a fascinating reading. It will appeal to anyone that has an interest in animal form and development, and also in genetics."--Evelyne Bremond-Hoslet, Mammalia

• Preface ix Part One: Forms and Numbers Chapter 1: Unity in Diversity 3 Two Skeletons 3 Clashes at the Museum 5 Squid and Vertebrate 7 Topsy-turvy 9 Chapter 2: Archetypes 11 The Primeval Plant 11 A Skeleton for Everyone 14 An Exemplary Crayfi sh 16 Chapter 3: Easy Numbers, Forbidden Numbers 18 The Scolopendra's Legs 18 The Nonexistent Variant 22 The Leech's Segments 23 Unexpected Arithmetic 24 The Giraffe's Neck 28 Indirect Effects 29 On the Fingers of One Hand 32 Number and Position 35 Chapter 4: Privileged Genes 38 Unity of Body Plan 38 The Universal Appendage 42 The Zootype 45 Position and Structure 48 "Master Control Genes" 50 Networks 53 Part Two: Constructing Form Chapter 5: Evolution and Development 59 Genes and Determinism 59 Possible Butterfl ies, Real Butterflies 63 Evo-devo 65 Chapter 6: The Logic of Development 68 From Mechanics to Molecules 68 The Lawfulness of "Monsters" 70 A Worm Enters the Scene 72 A Mosaic, or Perhaps Not 75 One Model, Several Models 76 The Adult's Questionable Uniqueness 77 Boxed Generations 78 According to Program 80 Cuticle, Cuticles 81 Cilia and Mitosis 86 Taking Development Seriously 89 Ontogeny and Phylogeny 90 Chapter 7: Paradigm Shifts 94 Science and Language 94 Gene, Genes 95 Busillis 97 Tissues 99 More on Segments 101 Origin, Form, and Function 103 Parallel Worksites 105 What Do We Start From? 107 Which Adult? 109 Siamese Twins and Corals 111 Spare Parts 113 Chapter 8: Comparisons 117 Horns and Antlers 117 Homology 119 One Gene, Several Effects 121 Ars Combinatoria 123 The Limits of Hierarchies 125 Organs, Only When All Is Done 127 Structures, Processes, and Developmental Stages 129 Chapter 9: The Body's Syntax 132 From Tip to Toe 132 The Dual Animal 134 The Sea Urchin 136 The Tapeworm 137 Part Three: Origins Chapter 10: Competition or Cooperation? 145 Apologues and Metaphors 145 The Species: From Inside and from Outside 146 Butterfl ies and Sea Urchins 148 Parasitoids 150 Throw-Away Larvae 150 Competition between Equals, or Not Quite 154 Germ and Soma 158 Authorized Competition among Equals 161 A Virtual Mouth 163 Embryonic Leafl ets 165 Who Is Winning? 167 One Egg, Several Embryos 169 Two Twins, or Rather One 170 Identical Twins, or Maybe Not 171 The Pupa's Balance Sheet 175 Competition and Cooperation: Two Sides of the Same Coin 177 Everything Small 178 Development in Stages 180 Chapter 11: Making and Remaking 183 Many and All Equal, or Few and Different 183 A Product of Factors 186 Calculations without Error 189 Broken Chains 194 Co-option 196 Buds and Appendages 197 Chapter 12: Innovations without Plans 201 Regularity without a Program 201 Inexpensive Symmetry 201 Breaks in Symmetry 204 The Origin of Evolutionary Novelties 205 Modules 208 A Glance at the Clock 209 Epilogue 211 Recommended Readings 215 Index 221