The answer to Marshall's opening riddle, "What do you get when you cross a tomato with a fish?" , almost was, and actually could someday soon be, found in your supermarket's produce section rather than in a joke book. As the author explains in this dry but methodical account, Dolly the sheep, the bovine growth hormone, a host of virus resistant cultivars, and the famous (or notorious, depending on your point of view) Flavr Savr tomato are only the beginning. Students looking for a discussion of the techniques and implications of gene splicing to create new types of food plants and animals will find this just the ticket.