Fig. 6. Immunostaining with antisera against amino acids and escapin in ink gland of Aplysia californica. Tissue is 0.5 µm thick plastic sections. A, B and C are from three different ink glands, each a set of four sections from the same region of tissue labeled with different antisera, i.e. antiserum against either escapin, alanine, taurine, arginine, cysteine or aspartate. `Preimmune' is the control, being labeled with preimmune serum. Vesicles labeled `a' are strongly immunopositive for many amino acids but not escapin; vesicles labeled `e' are intensely immunopositive for escapin but not for amino acids; vesicles labeled `c' are clear and not strongly immunopositive either for amino acids or escapin.