. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 3 TEETH 4 TEETH Fig. 80. Sertularella: internal teeth (adcauline side on right). In certain genera {Abietinaria, Amphisbetia, Calamphora, Crateritheca, Hydrallmania, Parascyphus, Sertularella, Sertularia, Symplectoscyphus and Thuiaria) contraction of the hydranth into the hydrotheca causes the proximal part of the gastral cavity wall to be folded into a blind caecum on the abcau- line side. This is due in part to the attachment of the ectoderm of this region to the hydrothecal wall preventing its com
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 3 TEETH 4 TEETH Fig. 80. Sertularella: internal teeth (adcauline side on right). In certain genera {Abietinaria, Amphisbetia, Calamphora, Crateritheca, Hydrallmania, Parascyphus, Sertularella, Sertularia, Symplectoscyphus and Thuiaria) contraction of the hydranth into the hydrotheca causes the proximal part of the gastral cavity wall to be folded into a blind caecum on the abcau- line side. This is due in part to the attachment of the ectoderm of this region to the hydrothecal wall preventing its complete withdrawal. This blind caecum is useful in generic diagnosis, but it must be borne in mind that it can only be observed in the contracted hydranth. It imparts a bilateral symmetry to the hydranth. In other genera the hydranth is withdrawn symmetrically into the hydrotheca and there is no caecum, Dictyocladium, Diphasia, Dynamena, Idiellana and Salacia. In Thyroscyphus withdrawal of the hydranth causes an annular folding all round the body, and Splettstosser (1929) considers this to be an early stage in the evolution of a blind Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original South African Museum. Cape Town : The Museum
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
