ABSTRACT
Systematics of the amphistomes is based on traditional principles and satisfies their purposes. Phylogenetic or biogeographic viewpoints have often been omitted from consideration. Adults amphistome type or monostome, evolving from amphistome plan; usually conical, strongly muscular in body; hermaphroditic with posteroterminally located, strongly developed acetabulum. Cercariae amphistome type with well-developed acetabulum. Eyespot and other pigmentation absent. Excretory vesicle thin-walled, saccate. Besides examinations of the phylogenetic relationships, based on holomorphological traits, the cytogenetic analysis can give further information to recognize tendencies in the evolutionary history of the amphistomes. Of the amphistomes a relatively small number of species has been studied karyologically; they are 12.2% of the total sum of species and were confined mainly to amphistomes parasitic in mammals. Karyotype analyses have revealed a newer scope of specific features which seem to be more reliable and substantial than those of morphological characters upon which the present systematics of amphistomes have mainly been based.
