COMPARATIVE EFFECTS OF LIGHT STIMULATION AND ADMINISTRATION OF GONADOTROPIC HORMONES ON FEMALE SPARROWS1

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Abstract
[female] sparrows (Passer domesticus) were exposed to lengthened daily light periods (electrical lighting) during fall, winter and spring. Exposure periods from 21 to 75 days induced only a moderate degree of ovarial development. The birds were partially refractory to injs. of gonadotropic substances in the fall. No refractory cases were found after Feb. Ovulation and eggshell formation were observed in several cases. The ineffectiveness of additional light periods indicates a low degree of responsiveness of the $ pituitary to light. Behavior factors, not given free play in the expt., are probably essential to the final hypophyseal stimulation and growth of ovaries to the breeding condition.

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