Chaetognaths, or arrow-worms, are voracious carnivores which are exceptionally abundant in all the seas of the world. It is highly likely that their vast numbers render them of major ecological significance in marine planktonic communities, yet very little is known of the group, largely because of the lack (until now) of easily accessible information about them. This first comprehensive survey deals with all aspects of chaetognath biology, including much recent and unpublished work.The twelve chapters of the book are contributed by leading scientists in chaetognath biology. Two chapters are devoted to taxonomic relationships both within the chaetognaths and between them and other animal groups; two chapters cover morphology and anatomy; four chapters are concerned with physiology and behaviour; three are devoted to ecology, including distributions and parasitism; and one chapter provides detailed information about the techniques necessary for studying chaetognaths.