There are well-developed longitudinal muscles in the tentacles. You saw evidence of their presence if you observed tentacular flicking. There is a pair of long lophophore retractor muscles extending from the posterior end of the zooecium to the base of the lophophore. These are easily seen in extended autozooids. You watched them operate when you induced the animal to retract earlier in the exercise.
Parietal muscles are present to extend the lophophore.
Briefly examine a retracted autozooid. Although their orientation with respect to each other has changed, you should be able to find the retracted lophophore and most of the regions of the gut. When the tentacles are withdrawn, they are enclosed by the retracted body wall. The space thus formed contains the tentacles and is the tentacle sheath . In Zoobotryon and some other bryozoans, there is a second chamber distad the tentacle sheath and similarly enclosed by the retracted body wall.