[Strobila periodicity of Spirometra (Cestoda: Diphyllobothriidae)]

The non-induced, endogeneous periodic destrobilation in Spirometra is conceived as an extreme of pseudapolysis. The patent time of S. erinaceieuropaei and S. sp. with single or with simultaneous infestations is arranged in separate patent periods marked off from each other by negative phases. This phenomenon is due to a periodicity of the strobila. In dissections during the negative phase only the scolex and neck alone or provided with a very short strobila could be found in the intestine. There were no striking differences between single and simultaneous infestations. The periodicity altogether, however, showed a great variability. A synchronization of the periodicity of egg shedding and destrobilation is concluded from one simultaneous infestation with demonstrably at least 2 tapeworms. After successive superinvasion, however, the periodicity evidently does not become synchronous, the periodicity of egg shedding is masked.