Figure 2

Comparison of the neuroarchitecture of the brain. a-c: Horizontal sections through the ventral lobes of the brain. The brain is composed of neuropil which is surrounded by densely packed somata. The ventral lobes are connected by the ventral commissural tract (vct). Posteriorly, the ventral part of the brain merges with the paired medullary cords (mc). Medially, the esophageal nerves (arrowheads in a) arise from the ventral lobes. Cephalic nerves (arrow in a) extend from the ventral lobes of the brain towards the anterior tip of the animal. The cerebral organs (co) are attached to the brain posteriorly (c-e). d-f: Horizontal sections through the dorsal lobes of the brain. The dorsal lobes are connected by a dorsal commissural tract (dct), as well. The brain is penetrated by the proboscis (p) which exhibits a cylindrical plexus in the immunostainings (d, g). g-h: Cross sections demonstrate that the brain and its commissural tracts form a ring surrounding the proboscis (p). cs cephalic slits. Scale bars: a,d,g,h = 200 μm; b,c,e,f = 500 μm.