AbstractEvidence for a direct neural projection from the retina to the hypothalamus in the golden hamster (Mesocricetus auratus) is presented. In 25 blinded animals degeneration was followed in sections prepared according to the Wiitanen ('69) silver impregnation method. Degenerative axons were found in the optic tract, chiasm, and nerve, terminating in the lateral geniculate body and superior colliculus. A large collateral bundle of degenerating axons was observed curving medially and dorsally to enter the hypothalamus at the level of the mamillary body. This bundle turned diffusely rostrally and terminated on neurons in the ventromedial nucleus of the hypothalamus.It is proposed that two alternate pathways exist for the effect of photoperiodicity on the reproductive cycle in the hamster, one involving the pineal gland directly and the hypothalamus indirectly, and the other a direct retino‐hypothalamic projection.