The entire internal anatomy of the squid can be seen in diagram E. The digestive organs and the sexual organs can be seen plainly in the center of the squid (DG) (Gd). These organs are protected from the outside by the mantle (M) which is the shield shaped tissue.
The nervous system of the squid is located underneath the internal organs and is composed of a Giant Axon (GA) and Stellate Ganglion (SG). Diagram B shows the mantle without the non-nervous system organs. The two Giant Axons (GA) can be seen running from the anterior (top) to posterior (bottom) down either side of the pen. The pen is the only remnant of the shell in squid.