part of start stage end stage epiphysis A circumscribed swelling, includes the pineal primordium that appears late in the segmentation period in the dorsal midline of the diencephalon. It is located directly rostral to the posterior commissure and dorsal to the habenular commissure. pineal organ zebrafish_anatomy corpus pineale ZFA:0000019 TAO:0000019 pineal gland visual system endocrine system pineal complex multi-tissue structure segmentation:10-13 somites adult