Figure 5: RER and granulate cells in the ink glands of Aplysia juliana ((a)–(d)) and A. parvula ((e) and (f)). (a) In RER cells the rer is closely appressed, only expanding into few vacuoles containing material of medium electron density or occurring as a whorl adjacent to the nucleus (b) or a Golgi-like stack of membranes with inflated tips (c). (d) A granulate cell has numerous dense granules, sieve areas, and a nucleolus. (e) RER cells have vacuoles containing dense material (arrows) appearing as dense granules with light microscopy (and similar in appearance to those in granulate cells). (f) These vacuoles contained aggregations of short, microtubule-like rods. ca, caveolae; Cmt, cross section of microtubule; g, dense granule; Lmt, longitudinal view of microtubule; m, muscle; mi, mitochondrion; n, nucleus; no, nucleolus; r, ribosome; rer, rough endoplasmic reticulum; sa, sieve area. Scale bars: (a)–(e) = 10 μm; (f) = 100 nm.