ABSTRACT
This chapter discusses some of the issues related to the organization of thalamus and cortex that bear on the topic of homologies between structures in reptilian and mammalian forebrains. There has been a considerable increase in knowledge of the connections of the reptilian forebrain since Huber and Crosby, LeGross Clark, and Ingvar postulated that the reptilian nucleus rotundus was homologous to the ventral group of nuclei of the mammalian thalamus based on its topography and cytoarchitecture. In order to establish probable homologies between thalamic and telencephalic cell groups in reptiles, it is necessary to examine the characteristics of individual thalamic nuclei. Recognizing that both reptiles and mammals show thalamic inputs to a visual area in the cortex raises the question of which systems are homologous in each group. The organization of the auditory system constitutes one dramatic divergence between reptiles and mammals.
