Comparative neurological studies of the evolutionary development of struc- tures within the central nervous system of vertebrates have depended to a large extent upon morphological rather than functional criteria. Classical comparative anatomical studies, which have attempted to demonstrate homologies between parts of the brain in representatives of different vertebrate classes may be grouped under three general headings: 1. comparison of the embryological development of brain structures; 2. comparison in adult forms of the topographical relations of neuron groupings and fiber tracts, and of...