XXXI.—The Life-History of Xenopus lævis, Daud

The present communication is intended to be the first of a series dealing with observations on the life-history of the Anura Aglossa and their anatomy at different stages of development. Xenopus lævis, with its small ova and protracted larval free-swimming stages, must necessarily form a basis for the study of the development of that other remarkable Aglossan, Pipa americana. Although the adult Aglossan is an aberrant and specialised Anuran, there are Urodele features in the development of Xenopas which make its embryology of great general interest. These primitive features, combined with others peculiar to the genus, impress a character upon the early life-history of this frog which is widely divergent from that of the Phaneroglossa with small ova.