BODY SIZE AS A FACTOR IN THE METAMORPHOSIS OF TADPOLES

¹ From the Physiological Laboratory, The University of Rochester School of Medicine and Dentistry, Rochester, N. Y.

1. Tadpoles of Rana sylvatica and R. pipiens if sufficiently retarded in growth by crowding did not metamorphose at the same ages as uncrowded ones. They were able to metamorphose at their small sizes at later times. Those only slightly retarded were able to metamorphose at the usual time, becoming small frogs.

2. Within certain limits a deficiency of body weight is compensated by a surplus of age, and a correlation of the two factors has been established. Through retardation of growth in size the larval stage can be greatly prolonged. Body size is therefore a tangible quantitative factor in the complex of conditions which regulate the onset of metamorphosis.

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