NEURAL PROJECTIONS OF THE PINEAL ORGAN IN THE LARVAL SEA LAMPREY (PETROMYZON-MARINUS L.) REVEALED BY INDOCARBOCYANINE DYE TRACING

The distribution of the central neural connections of the pineal organ of the larval sea lamprey was investigated by means of anterograde an d retrograde tracing with the fluorescent lipophilic dye, DiI (1,1'-di octadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate). Pinealof ugal projections are well developed in larvae, extending from the post erior commissure into the diencephalon and mesencephalon. Small number s of neurons were retrogradely labelled in the transition zone between the diencephalon and the mesencephalic tegmentum. These cells may con stitute the first pinealopetal system described in anamniotes.