Pentactaea sentence example
- Semon called this stage the Pentactula, and supposed that, in its early history, the class had passed through a similar stage, which he called the Pentactaea, and regarded as the ancestor of all Echinoderms. It has since been proved that the five tentacles with their canals are interradial, so that one can scarcely look on the Pentactula as a primitive stage, while the apparent simplicity of the Synaptidae, at least as compared with other holothurians, is now believed to be the result of regressive vlu.
- The Pentactaea, at all events as it sprang from the brain of Semon, must pass to the limbo of mythological ancestors.
- The Pentactaea again suggested a search for some primitive type in which quinqueradiate symmetry was exhibited in circumoral appendages, but had not affected the nervous, water-vascular, muscular or skeletal systems to any great extent, and the generative organs not at all.