Removal of the eyes (Reiter, 1968) or of the olfactory bulbs (Orbach & Kling, 1966) slightly delays gonadal maturation in rats. The gonadal inhibitory effect of blinding is prevented if animals are pinealectomized (Reiter, 1968 ). It was found recently that if weanling male rats have both their eyes and olfactory bulbs removed, the testes are less than half their normal size at 70 days of age; this entire effect is reversed if the animals also have their pineal gland removed. This indicates

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... another external factor, in addition to the photo-period, may influence directly or indirectly the antigonadotrophic activity of the pineal gland. The experiment was repeated and the following data illustrate some interrelationships between olfaction, photo-period, the pineal gland and reproduction. Sixty-four 21to 23-day-old male Sprague-Dawley rats were divided into seven groups (Table 1 ). Although not indicated in the Table or mentioned hereafter, all non-pinealectomized animals were subjected to a sham pinealectomy; this operation had no apparent effect on the results. The methods for performing real pinealectomy (Hoffman & Reiter, 1965) and blinding (Reiter, Sorrentino, Hoffmann & Rubin, 1968) have been previously described. Olfactory bulbs were aspirated with mild suction through two holes (2 mm diameter) which were drilled in the skull overlying these structures. Animals were kept two to a cage in temperature-(23\m=+-\2\ s=deg\ C) and light-(14 hr of light/day) controlled rooms. Light was provided by 40-watt 'cool white' fluorescent bulbs with an intensity of 20 to 85 footcandles within the cage. Food was placed on the floor of the cages to ensure that it could be found by all animals. Rats were killed, between 10.00 and 13.00 hours, at 68 days of age and the testes, seminal vesicles and coagulating glands were weighed and prepared for microscopy. Pineal glands of non-pinealectomized rats were weighed and assayed for their content of hydroxyindole-O-methyltransferase (HIOMT) according to the method of Axelrod, Wurtman & Snyder (1965). HIOMT, an enzyme found only within the pineal gland of mammals, is required for the synthesis of melatonin, a pineal antigonadotrophic substance (Wurtman, 1967) . Blinded rats (Table 1 , Group 2), as expected, had smaller than normal reproductive organs (absolutely and relatively) unless they were pinealectomized (Group 3). Anosmia, alone (Group 4