Besides the apical tuft, the apical plexus directly underneath the apical tuft may belong to the ground pattern
of apical organ structures in Neuralia, as it is commonly
innervated by flask-shaped, neuropeptidergic sensoryneurosecretory cells from the apical plate or apical organ
proper - in mollusks [101,102], sea urchins [78], hemichordates [74] and, likewise, cnidarians [85,103-107].