Fig. 4. Localisation of calcium in the swimming muscle of Polyorchis penicillatus by potassium dichromate precipitation. (A) Within the nucleus, grainy electron-dense precipitates (EDPs) can be seen. (B) Vesicles in the somal region show a high calcium content. The arrowhead indicates the plasma membrane, showing EDPs located on the inner side of the membrane. (C) Vesicles (arrow) in the subsarcolemma (arrowhead) contain EDPs. (D) Large vesicles between mitochondria and myofilaments in the subsarcolemma contain EDPs (arrow), which are located on the inner side of the membrane. The arrowhead indicates the sarcolemma membrane. Mi, mitochondria; Me, mesoglea. All scale bars are 1 µm.
