From the Reviews of Previous Volumes "In reviewing this volume as a whole, one is struck by the quality and scholarship of the various chapters and the obviously efficient editing." -PARASITOLOGY "The policy of the editors of Advances in Parasitology to include reviews from any aspect of parasitology and the high standard of individual papers have resulted in this series of volumes becoming an indispensable source for students, teachers, and research workers." -ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY