Black droplets of oil are seen in the epithelial cells lining the secreting tubules.
Belonging primarily to the epithelial layer, the muscular cells may become secondarily sub-epithelial.
The epithelial layer consists of (1) so-called " indifferent " cells secreting the perisarc or cuticle and modified to form glandular cells in places; for example, the adhesive cells in the foot.
The sub-epithelial layer consists primarily of the so-called inter stitial cells, lodged between the narrowed basal portions of the epithelial cells.
The ovaries are epithelial sacs which open into the uteri.