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To even consider writing a book on comparative placentation is daunting, given the diversity that is found in placental structures. That the authors have carried this off, providing in compact form an excellent indication of the extent of diversity and the fascinating ways in which placentas form and function, is remarkable.

The first two chapters of the book provide an introduction and information concerning implantation, exchanges between maternal and fetal components, and vascular relationships. Although these chapters include the most comments concerning function, such comments also appear in subsequent more morphologically oriented chapters. The third chapter on non-mammalian vertebrate placentation (fish, amphibian, bird and reptile) brings together diverse papers to lead one into this interesting area. The fourth chapter is on monotreme and marsupial placentation. The next four chapters are on placentas of eutherian mammals, arranged by morphological relationship of the interhemal areas of the chorioallantoic placenta. They are on epitheliochorial, synepitheliochorial, endotheliochorial, and hemochorial placentas, respectively. In each chapter considerable information on a few examples is given. Although the commonly used animals receive the most attention, the presence of some other species with each placental type is often added. The ninth chapter introduces the subjects of placental immunology, viviparity, and briefly evolution, and the final chapter of only three pages is entitled hybridisation, cloning and fetal origins of adult disease.

There are no colour illustrations, but the abundant micrographs are very well-selected and also well-reproduced. Figure 6.17 of the 50-day goat placenta is perhaps the finest low-magnification electron micrograph I have ever seen! The numerous drawings add clarity although often presenting some compromises as drawings inevitably do. For example, in figure 1.2 they have amnion formation in the human by splitting, whereas in the text it is more accurately by cavitation. They also have an allantois with a considerable allantoic cavity in human development in this drawing.

In gathering together and integrating so much information, personal choices must be made and individual investigators will find statements with which they would quibble, and a few errors can be found. However, these minor problems detract little from the book.

Anyone with a smattering of knowledge of placentation could open this book almost anywhere and find interesting information. Someone who has worked only with one species should perhaps look first at the introductory chapters. The index is minimal. However, one of the major advantages of the book is the presence of an extensive outline in the table of contents, allowing the reader to quickly go to an area that might be of special interest. This is not a compilation of data on all families, nor do the authors agonize over definitions. I personally would use some terms differently, such as trophoblast, which has precedence over trophectoderm, which also suffers from being used differently in different species. Their definition of decidua is so broad that they state “In most primates…decidualisation starts before fertilization…” This statement may be a bit confusing to readers who know that differentiation of decidual cells per se occurs after implantation in this group.

The overall result is that the book is readable rather than overwhelming. A great deal of interesting information is available, and readers can use the extensive bibliography to look for more information on subjects presented in this appealing book. Helpfully, in the text the authors refer directly to the senior author of each paper rather than using numbers, making it easier to keep in mind the sources of the information.