Book excerpt: Advances in Comparative Physiology and Biochemistry, Volume 3 focuses on phylogenetic and taxonomic value of enzyme variation between species; synthesis of proteins in the formation of specialized cells; and how organisms metabolize compounds. The selection first offers information on variation in enzyme structure and function and molecular aspects of cytodifferentiation. Discussions focus on molecular basis of enzyme evolution, genetic basis of evolution, technical difficulties in the comparative study of enzymes, and enzyme evolution and phylogeny. The text then takes a look at the comparative metabolism of xenobiotics, including oxidations, reductions, dechlorinations and dehydrochlorinations, bromination, formation of peptides, acetylation, and evolutionary and taxonomic aspects of detoxication. The manuscript examines the biochemistry of supporting materials in organisms and crustacean metabolism. Topics include survey of natural supporting materials, properties of supporting materials and their consequences, carbohydrate and lipid metabolism, terminal oxidation and energy production, and enzymes, pigments, and biochemical adaptation to environment. The selection is a valuable reference for readers interested in the developments in the processes, methodologies, and approaches in comparative physiology and biochemistry.