• Table of Contents
• Preface

Table of Contents

Section I. INTRODUCTION

Chapter 1 Characteristics of Metazoan Development
Gary J. Brusca, Richard C. Brusca, and Scott F. Gilbert

Chapter 2 The Concept of Larvae
Paul E. Fell

Section II. PRIMITIVE MULTICELLULAR ORGANISMS

Chapter 3. Dicyemid Mesozoans
Piroschka Horvath

Chapter 4 Porifera, the Sponges
Paul E. Fell

Section III. RADIATE ANIMAL PHYLA

Chapter 5 Cnidarians, the Jellyfish and Hydras
Vicki J. Martin

Chapter 6 Ctenophorans, the Comb Jellies
Mark Q. Martindale and Jonathan Henry

Section IV. BILATERAL ANIMAL PHYLA: ACOELOMATES AND PSEUDOCOELOMATES

Chapter 7 Platyhelminths, the Flatworms
Charles H. Ellis, Jr. and Anne Fausto-Sterling

Chapter 8 Nematodes, the Roundworms
Einhard Schierenberg

Section V. BILATERAL ANIMAL PHYLA: PROTOSTOME COELOMATES

Chapter 9 Nemerteans, the Ribbon Worms
Jonathan Henry and Mark Q. Martindale

Chapter 10 Sipunculans and Echiurans
John F. Pilger

Chapter 11 Gastropods, the Snails
J. R. Collier

Chapter 12 Annelids, the Segmented Worms
Marty Shankland and Robert M. Savage

Chapter 13 Arthropods: The Crustaceans, Spiders, and Myriapods
Scott F. Gilbert

Chapter 14 Arthropods: The Insects
Fritz E. Schwalm

Chapter 15 The Lophophorate Phyla: Phoronida, Brachiopoda, and Bryozoa
Russel L. Zimmer

Section VI. BILATERAL ANIMAL PHYLA: DEUTEROSTOME COELOMATES

Chapter 16 Echinoderms
Gregory A. Wray

Chapter 17 Tunicates
William R. Jeffery and Billie J. Swalla

Chapter 18 Cephalochordates, the Lancelets
J. Richard Whittaker

Chapter 19 Fishes
James Langeland and Charles Kimmel

Chapter 20 Amphibians
Richard Elinson

Chapter 21 Reptiles and Birds
Gary Schoenwolf

Chapter 22 Mammals
Yolanda Cruz

Section VII. PLANTS

Chapter 23 Plant Life Cyles and Angiosperm Development
Susan R. Singer

Preface
Why, in the last years of the twentieth century, would one want a new embryology book? Didn't developmental biology replace embryology? Wasn't the phenotypic science of embryonic anatomy put on a cellular and molecular basis during the last half of this century?

There are several ways to answer the question as to why a new embryology book is needed. The first answer is that the replacement of embryology by developmental biology has been very selective. Only a few organisms--the fly Drosophila melanogaster, the nematode Caenorhabditis elegans, the frog Xenopus laevis, the mouse Mus musculus, and, increasingly, the fish Danio rerio, the chick Gallus domesticus, and the primate Homo sapiens--have been privileged to be studied on the molecular level. In other words, of the millions of insect species, only one is known on a significant developmental level; of the millions of amphibians, only one species represents the whole remarkably diverse class.

The second answer, contingent on the first, is that without knowledge of many other species, one cannot due significant comparative studies. There is much new material in this volume. Indeed, we are beginning to see a Renaissance of embryological studies. Where new techniques are being utilized, major changes are being wrought in our knowledge of embryos.

The third answer is that without knowledge of many other species, one cannot due significant evolutionary studies. Macroevolution is increasingly being seen as being caused by changes in developmental processes. This renewed interest in the causal mechanisms of macroevolution is fueling a new generation of studies in comparative embryology, and oligonucleotide probes are complementing traditional dyes in this analysis.

The fourth answer is that textbooks of developmental biology have become upper-level courses dependent upon one's students having some knowledge of cell biology and genetics. This has created a vacuum at the sophomore level. Students come to our developmental biology classes remarkably aware of transcription and translation but knowing nothing about the teloblasts or neural crest cells. Students have to know the "what" before they can ask the "how." Dollinger, the mentor of von Baer, noted that students must first be shown the embryo. Then they will ask the appropriate questions as to how these changes can possibly occur. We hope that this Embryology book will inspire students to learn the "what" and ask those "how" questions that are addressed in the developmental biology texts.

The fifth answer is that textbooks in developmental biology (such as that written by one of the editors) report the success stories. They discuss the materials about which we know the most. This Embryology book is going to discuss the things we don't know. While developmental biology books highlight the development of those few organisms that have been extensively studied, this Embryology book is going to report about those organisms whose development is not well known. The student of developmental biology should discover whole new worlds to explore. The organisms of most animal classes have not had their fate maps drawn with new markers nor had their patterns of gene expression probed.

The sixth answer is aesthetic. Most of the older developmental biologists have entered the field because of a fascination with the beauty, order, and interactions of real developing organisms. Whole embryos and larvae are wonder-full forms of life and should be brought back into the curriculum. Embryos and larvae have suffered from the negative connotations that Western culture has placed on things ephemeral and transitional. The adult is valued more than the transitory stages that came before it. Being is valued higher than becoming. But embryology is a science of becoming. It is a science of emerging complexity; hense it may be the science of the next century. When one realizes that the adult Cecropia moth flies only once to find its mate and then dies, one realizes that the larval stages are not a small portion of the moth's life.

This book sees a continuity between the changing anatomy emphasized in Embryology courses and changing patterns of cells and gene expression emphasized in developmental biology courses. One approach cannot be complete without the other. Alfred North Whitehead (a philosopher of process and change much admired by embryologists of the 1930s and 1940s) wrote that there is no true distinction between the reality of an object and the processes that cause its being. This is consistent with our studies in development.

This is a "timeless" book. No contributor had the time to write it. Each chapter is an act of love from the author to the readers. Each author wanted to write these chapters to introduce students to the wonderful organisms that are so worthwhile to know. It is to them that we owe a big thank you. Scott's job was to round up these people and convince them that if they didn't write these chapters, students wouldn't be introduced to the incredible organisms they study. Anne's job was to read these chapters and to make certain that someone with a basic biological knowledge (but not a specialist's insight) could understand them. Although it has been fun putting these chapters together, it made the editors nostalgic for the summers that they were at the shore studying the embryology of some of these organisms. There is no substitute for seeing the real creature.

Scott F. Gilbert
Anne Raunio