undulating membrane un·du·lat·ing membrane (ŭn'jə-lā'tĭng, ŭn'dyə-, -də-)
An organelle of locomotion in certain flagellate parasites consisting of a finlike extension of the cytoplasmic membrane with the flagellar sheath.
The peristome is in the posterior half of the body and an undulating membrane extends from it into the œsophagus.
The right edge of the peristome supports an undulating membrane.
Upon the left edge of the peristome is a high, undulating membrane, sail-like in appearance when extended.
On the right border of the peristome is an undulating membrane.
I do not believe these could be the moving edge of an undulating membrane, for they are quite distinct.
Inside the oral depression is a second undulating membrane, running down to the mouth.
Each side of this groove bears an undulating membrane, the left being much larger and conspicuously striated.
The peristome is long and rather narrow and carries an undulating membrane on its right margin.