An ultrastructural study of the thyroid gland in the pre-metamorphic Xenopus laevis (Daudin) tadpole.

A simple method for obtaining the thyroid tissue of anuran tadpoles for ultrastructural study has been described. Follicle and colloid formation in the thyroid gland have been observed in Xenopus laevis tadpoles at an early stage. The activity of the thyroid gland of pre-metamorphic tadpoles does not seem to depend on the activity of the hypophysis cerebri and the hypothalamus. Both 'light' and 'parafollicular' cells are present in the thyroid gland of premetamorphic Xenopus laevis tadpoles.