Abstract
A biological investigation of cercarial dermatitis in Manitoba has revealed that three species of apharyngeal brevifurcate cercariae are responsible for the disease. An ecological study of the organisms and their molluscan hosts has been carried out, and descriptions of the general types of habitats are given in addition to the distribution of the organisms. A synopsis of the dermatitis-provoking cercariae and the adult schistosomes of the world is given, and the classification of the adults is revised in part. The results of a survey of mammals and birds for adult schistosomes and also the results of experimental exposures of animals are included. A new species of apharyngeal brevifurcate cercaria and two new species of Ornithobilharzia are described. The description of Cercaria wardlei McLeod, 1934, is revised.