For some time Rockefeller U.'s Donald Griffin has raised the question of whether animals are capable of conscious thought--insects and other invertebrates, as well as primates. Coming from a distinguished investigator, such ideas axe not so easily dismissed. In landmark studies 30 years ago, Griffin established that many species of bat locate their prey in the dark by emitting ultrasonic signals and then listening for the echoes as the sounds bounce off the bodies of tiny insects. (Later, colleagues discovered that the bat's moth-prey had auditory receptors that could pick up the bat signals and trigger evasive actions.) Now Griffin has formalized his conjectures in an elegant and gracefully written review of laboratory and field observations of a wide range of species. To his credit, he continues to raise questions rather than assert dogmatic hypotheses--so that even hardnosed skeptics (and diehard behaviorists) can pursue alternate explanations. For the general reader--which could include high school students--the examples are intrinsically fascinating. Griffin extends the familiar examples of waggle-dancing bees, termite-fishing chimpanzees, and rock-using otters to new and subtle heights. We learn that vervet monkeys have distinct alarm cries that signal whether an eagle, python, or leopard has been sighted. We begin to wonder, with Griffin, if the beaver conceives the pond in the mud and branches dragged through the water. There is much on predator-prey behavior, on mating, nest-building, parental care, on social insects, and on the many varieties of animal communication. In due course, Griffin also probes the various definitions of thinking and consciousness and, importantly, suggests the kinds of experiments that might yield answers. Altogether: a wonderfully provocative and always absorbing book.