BODY SIZE AS A FACTOR IN THE METAMORPHOSIS OF TADPOLES

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Abstract
Tadpoles of Rana sylvatica and R. pipiens were weighed and observed at intervals of 1 to 5 days during metamorphosis. Emergence of the forelegs was taken as the time (age) of comparison. When sufficiently retarded in growth by crowding, they did not metamorphose at the same ages as those not crowded but metamorphosed later while still small. Meanwhile those only slightly retarded in growth at 19[degree] C. metamorphosed at the usual time, becoming small frogs. Within certain limits a deficiency of body weight was compensated by a surplus of age, and a correlation of the two factors was drawn. Through retardation of growth in size the larval stage could be prolonged to 3 or 4 times its usual duration. Body size is therefore a tangible quantitative factor in the complex of conditions regulating the onset of metamorphosis.