| 1. | The paired pedal protractor and retractor muscles operate the animal's foot.
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| 2. | The penis retractor muscle is situated beside the right tentacle.
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| 3. | A set of retractor muscles help pull the proboscis back inside the sheath once feeding is completed.
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| 4. | The apparent absence of retractor muscles correlates with " Ancalagon "'s inability to significantly invert its proboscis.
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| 5. | It snaps back in because the retractor muscles start to tense up even before it reaches its target.
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| 6. | _The long retractor muscles, anchored in the hips, start to tighten even before the tongue is all the way out.
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| 7. | Sheath; with a single retractor muscle, inserting rather close to the beginning of the vas deferens, without a flagellum or caecum.
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| 8. | retractor muscle contracts to retract the penis into the sheath and relaxes to allow the penis to extend from the sheath.
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| 9. | The retractor muscles : The buccal mass and pedal retractors are fused together posteriorly where they unite with the Helix ".
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| 10. | As this structure is embedded in the retractor muscle itself rather than extraneous to it, it may represent a unique development in animals.
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