Without photos, the translucent, gelatinous aspect of the jellyfish is impossible to grasp; without adequate drawings and diagrams it is difficult to understand his curious umbrella-like structure (there's a side view but none from below) or his complex life cycle; and--to be picky--the dramatic coloration of many jellyfishes is obscured in black-and-white. All the more to be regretted because the jellyfish is ipso facto fascinating and the text pinpoints much that is known--and, equally interesting, not known--about him. Besides information on structure, sense perception, protectiveness, mode of swimming and feeding, fertilization and successive transformations--all the fundamentals--there are chapters on famous and rare forms (including the Portuguese Man-of-War) and the history of jellyfishes. And, for youngsters who want to investigate further, instructions on making a model, observing a live specimen, avoiding stings and treating them if you don't. Also an appropriate bibliography. Though self-limited, this is still the fullest source on the subject.