. The biology of the amphibia. Amphibians. 278 THE BIOLOGY OF THE AMPHIBIA and Bufo vulgaris & temperature of 25° produces a very high excess of males. A temperature of 20° is neutral in the toad but has a slight masculinizing effect in the frog. In the toad the reversal of sex has apparently been accom- plished but under different conditions. In the tadpole of Bufo, the anterior portion of each gonad becomes enlarged and in the adult, forms the Bidder's organ, a structure which has been frequently compared to a rudimentary ovary. Harms (1926) and Ponse (1926) found that removing the teste
. The biology of the amphibia. Amphibians. 278 THE BIOLOGY OF THE AMPHIBIA and Bufo vulgaris & temperature of 25° produces a very high excess of males. A temperature of 20° is neutral in the toad but has a slight masculinizing effect in the frog. In the toad the reversal of sex has apparently been accom- plished but under different conditions. In the tadpole of Bufo, the anterior portion of each gonad becomes enlarged and in the adult, forms the Bidder's organ, a structure which has been frequently compared to a rudimentary ovary. Harms (1926) and Ponse (1926) found that removing the testes caused the Fig. 100.—Sex reversal in a toad. Three and a half months after removing the testes of the adult toad, part of the Bidder's organ has developed into an ovary. B., urinary bladder; , fat body; Liv., liver; Ov., rudimentary ovary. {After Harms.) Bidder's organ to develop into a functional ovary (Fig. 100) If Bufo is assumed to be hermaphroditic, this would not be a case of sex reversal but merely a growth of the ovary after the inhibitory effect of the testes was removed (Ponse, 1927). The cells of Bidder's organ, however, have the appearance of indiffer- ent germ cells which, although potential sperm, are transformed into ova by the conditions of the experiment. Sex reversal has also been accomplished in salamanders in a more decisive manner. Burns (1925) joined pairs of Ambystoma together at an early stage before sex differences in the gonads were visible. When the salamanders developed, the sex of the mem-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Noble, Gladwyn Kingsley, 1894-1940. New York : McGraw-Hill
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