Abstract

James Valentine's "On the Origin of Phyla" is divided into three main sections: "Evidence of the Origins of Metazoan Phyla," "The Metazoan Phyla," and "The Evolution of the Phyla." The second section is the zoological core of the book, a more or less conventional treatment of major animal taxa, arranged in chain-of-being fashion from sponges to cnidarians to "worms" of many kinds, and so onward to arthropods, echinoderms, chordates, and all others in between. Philosophically inclined readers will be most interested in the first and third sections of the volume, which treat phylogenetic principles and macroevolution respectively. These sections are rich in detail, but Valentine adopts something of a rear-guard position on many issues, arguing in favor of a number of concepts that most systematists have now abandoned. The publisher's advertisement describes "On the Origin of Phyla" as "one of the classic scientific texts of the twentieth century," and for us in the 21st century, that may be the best way to regard it. It will be of greatest value to zoologists who want a good compendium of current comparative data, and to historians and philosophers of science who have an interest in the complex development of phylogenetic "tree-thinking" in systematic biology.