Fig. 4

Immunohistochemistry of Owenia fusiformis a: Numbers indicate the different tentacles (1–4) of the tentacular crown. The brain ring gives rise to two main nerves (arrowhead) per tentacle. The tentacle epidermis contains a fine nerve plexus (tp). ca: caudal; fo: frontal; tc: tentacle crown. b: Lateral part of the brain ring. The neurites (ne) of the brain (br) ring are arranged in parallel. No tracts are discernable. Somata (so) are distributed along the course of the neuropil. c: Detail of B. Somata (so) are of the same small type. ne: neurites. d: Cross section of epidermis. Sensory cells (sc) are located inside the epidermis (ep) and are connected to the epidermal plexus (epp). e: Posterior to the brain an epidermal plexus (epp) is present. Neurites (ne) are arranged in a net-like manner