SCANNING ELECTRON-MICROSCOPY OF SUPPORTING CELL CRYSTALS IN THE LARVAL PINEAL ORGAN OF THE LAMPREY, GEOTRIA-AUSTRALIS (GREY)

In order to demonstrate (a) the arrangement and shapes of crystals wit hin the supporting cells of the larval pineal organ of Geotria austral is and (b) the presence or absence of ''projecting knobs'' into the pi neal lumen, ten specimens were examined under the scanning electron mi croscope. No cellular protrusions were noticed and the crystals, being approximately 0.8 mum long and 0.4 gm wide, were found to be both num erous and randomly oriented. The absence of any kind of alignment or l ayering of the crystals is interpreted by us as a sign that the princi pal function of the pineal organ is that of a detector of ambient ligh t levels rather than that of an image-forming ''third eye''.