Figure 34.25: Evolution of the Vertebrate Brain A reasonably representative brain of a modern species in each group is shown. In the mammal, the large cerebral hemispheres keep us from seeing the pituitary, which is found in a position similar to other groups. The optic tectum is involved in processing visual information. Medulla oblongata, a term used with several variations in exact meaning, is here used in its most general sense.