Herdmania shows brain or nerve ganglion. It is 4 mm long. It is present in the mantle in between the two siphons. A neural gland is present above the brain. From the brain three nerves arise, one goes to the bronchial siphon, and two will go to the atrial siphon. The brain represents the degenerated nervous system of the larva.
- Red pigmented spots on the test are photoreceptors. They are sensitive to light.
- Sensory cells of the margins of siphons and tentacles are tango receptors. They are sensitive to touch.
- The cells on the margins of siphons are rheo receptors. They are sensitive to water currents.
- Cells lining the siphons are thermo receptors. They are sensitive to changes of temperature.