Fig. 1. Lateral views of the brains of a number of extant vertebrate species (the brains are not drawn to the same scale). While there is tremendous variation in both overall brain size (see Fig. 2) and the size of most brain divisions, most vertebrates possess brains that can be divided into the same number of divisions. aob, accessory olfactory bulb (cross-hatched); cb, cerebellum (stippled); ch, cerebral hemispheres (cross-hatched); m, medulla oblongata; ob, olfactory bulb (cross-hatched); ot, optic tectum (black); and p, pituitary gland. Modified from Braun and Northcutt (1999)