[Anatomy of the neural apparatus of cestodes of the families Amphicotylidae and Diphyllobothriidae (Pseudophyllidea)].

Studies were carried out of the nervous apparatus of Eubothrium salvelini, E. rugosum, E. crassum, E. vittevitellatus, Diphyllobothrium latum and D. dendriticum (Cestoda, Pseudophyllidea) at different stages of their life cycle. Scolexes of adult cestodes are innervated with 5 pairs of longitudinal nerve trunks, the number of which in the strobile gradually increases up to 17 pairs in species of Eubothrium and up to 60 pairs (in the wildest parts of the strobile) in species of Diphyllobothrium. There were noted differences in of longitudinal trunks in different species and in the specimens of the same species but from different hosts, the width of the strobile being the same. The main lateral trunks are situated in the medullar parenchima. In species of Eubothrium they are wide apart while in Diphyllobothrium they are drawn closer to one another. The description of the rough and inner nerve plexuses is given. Judging by the larval developmental phases the well developed orthogon with 3 pairs of longitudinal nerve trunks can be taken for the initial state of the nervous apparatus in Pseudophyllidea. This means that the initial forms belonged to advanced turbellarians rather than to primitive ones.