Tadpole grows with no morphological changes. Accelerated growth of hind limbs. Tail is resorbed. Shape of head changes. Gills are replaced by lungs.
Ocular muscles develop.
Change from ammonia excretion to urea excretion. C. Endocrine control. Friedrich Gudernatsch fed horse thyroid to tadpoles, causing premature metamorphosis. T 3 and T 4 levels are low during premetamorphosis and peak during metamorphic climax. Thyroidectomy or antithyroid drugs inhibit metamorphosis.