The primitive shell-sac or shell-gland is well marked at this stage, and the pharynx is seen as a new ingrowth (the stomodaeum), about to fuse with and open into the primitively invaginated arch-enteron (fig. [Please select]
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Like the Floscule, the Stephanoceros is readily alarmed, and retreats into her house, carrying with her the invaginated portion. [Please select]
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The dead outer layer or ectocyst lines part of the portion thus invaginated and forms the walls of a cavity within the orifice. [Please select]
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The diaphragm, however, does not constitute the limit of the invaginated portion of the zooecium, for the living inner wall or endocyst is dragged in still further and forms a sheath round the retracted tentacles. [Please select]
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