Numerous investigations have been carried out in an effort to determine the significance of the pineal eye as a photoreceptor. Francotte (1897) cauterized the eyes of the lizard Anguis fragilis and tested the receptive functions of the pineal eye. His results, while inconclusive, suggest that this organ may act as a light receptor in this species of lizard. Nowikoff ('07) studied the effect of light on the pineal eye in the lizards Lacerta agilis and Anguis fragilis and showed that the movement of pigment granules in the retina of the pineal eye was dependent upon the intensity of light used as a stimulus. Dendy ( ,ll) focused a light of relatively high intensity above the pineal eye of the Rhynchocephalian Sphenodon punctatus and failed to observe any resulting influence. Clausen and Poris ('37) showed that the pineal of Anolis carolinensis was not the primary avenue of light reception for testis activation but that obliteration of the pineal eye resulted in an accelerated testicular activity. It was suggested in this investigation that light reception through the pineal eye might however act as a n inhibition of testicular activity by some indirect means.
I n the following series of experiments an attempt has been made to determine, by comparative oxygen consumption tests, whether o r not the pineal eye served as a photoreceptor in the lizard Anolis carolinensis. Throughout the following discussion we will use the term pineal and restrict its use herein to that specific structure of the ephiphyseal complex generally referred to as the parietal eye in most reptiles. A preliminary report of the results was published in abstract form (Clausen and Mofshin, '36). This investigation has been aided by a grant from the Josiah Maoy, Jr. Foundation.
a Assistance in the preparation of these materials was furnished by the personnel of Works Progress Administration Official Project No. 465-97-3-67.