Figure 2.

CNS organization along the anterior-posterior axis in ascidians and vertebrates. Left is a schematic drawing of the vertebrate CNS compartments indicated as boxes, with forebrain colored in red, midbrain in orange, mid-hindbrain (MHB) in green, hindbrain in tan and spinal cord in yellow. Right are four models of the ascidian CNS with the different morphological compartments (sensory vesicle, neck, trunk ganglion and tail nerve cord) indicated as boxes. Colors indicate equivalence to vertebrate CNS compartments in four different models. White indicates no (or uncertain) homology. Models are based on information in [63]-Model i; [44]-Model ii; [57]-Model iii; with Model iv showing an integrated summary of previous and recent data (see text for details).