The justification of the following paper is found in the fact that, notwithstanding the investigations of Dugés (1834), Gegenbaur (1861, 1862, 1876), Goette (1875), Schwegmann (1884), Hasse (1892), Peter (1895), Gadow (1896), Ridewood (1897), Kapelkin (1900), Schainsland (1906), and Emelianof (1925). which deal with the vertebral column in Anura, there still remains a great deal of uncertainty as to formation of the centrum. We are not certain, first, whether the Anuran centrum is formed from the dorsal arcualia or has an independent origin; secondly, whether the intervertebral body is formed from the dorsal arcualia, or has an independent origin; thirdly, whether any change takes place in the developing vertebra as it passes from its cartilaginous condition to its ossified stage, for none of the above-mentioned workers have traced it up to its full development in the adult condition; fourthly, how the ninth vertebra, both in the case of Rana temporaia and Bufo melanostictus comes to have two condyles to articulate with the urostyle; fifthly, how the first (atlas) vertebra develops, and what is its relation to the occipital region ; lastly, how the Anuran skull has developed two condyles for articulation with the first vertebra. The writer desires to acknowledge his indebtedness to Prof. E. W. MacBride, who with valuable advice and criticism has greatly facilitated these researches. He has also to acknowledge his obligations to Mr. H. R. H ewer*, Mr. N. Murti, Mr. P. Gray, and Mr. C. John for their kind assistance, which has led to the improvement of this paper.