Abstract
Summary
Adult female starlings in the quiescent season are a favorable material for the study of the biological properties of natural and synthetic sex hormones. Their ovaries and oviducts are capable of increasing in weight 100 to 150 times and the wolffian ducts 10 to 20 times. The bill color and the wolffian ducts react only on stimulation by androgens while the oviducts react in an identical way on either male or female hormones. Stilbestrol produces purely gynogenic effects and is considerably more potent than equal doses of estrone. Progesterone even in high doses or in combination with estrone gives no effects; it does not seem to be one of the hormones that take a part, normally, in the endocrine physiology of passerine birds.
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