[Embryonic development of three Cestoda from the genus Acanthobothrium (Tetraphyllidea, Onchobothriidae) (author's transl)].

The embryonic development from the egg to the oncosphere is examined in three Cestoda: Acanthobothrium coronatum (Rud., 1819), Acanthobothrium filicolle, Zschokke, 1888 and Acanthobothrium zschokkei Baer, 1948 (Tetraphyllidea, Onchobothriidae). The three ontogeneses have in common the following data: -- Two vitelline cells pass with the zygote into the ootype where a thin shell is formed out of a material which comes from the vitelline cells. -- At first the cleavage is equal, then it becomes unequal resulting in the formation of four types of blastomeres: macromere, secondary macromere, mesomere and micromere. -- The preoncospheral phase is characterized first by the blastomere multiplication and later by their decreasing number and differentiation. -- The embryonic envelopes are formed within the shell. The vitelline layer includes the cytoplasm, a vitelline nucleus and possibly the secondary macromere, the nucleus of which always lies against the outer membrane of this envelope. The syncytial embryophore develops from mesomeres coming from the embryo. -- The oncosphere is limited by its owm membrane whose posterior region seems to double in order to form a kind of cap bending over the six hook tips. The final number of embryonic hexacantha cells is relatively low.