Before submitting to the Royal Society a third paper on the Skull of the Batraehia, it would seem to be better for me to bring forward the results of my work on one of the simpler kinds of Amphibia, namely the Axolotl, a type belonging to the “Urodela.” Through the kindness of friends I have been enabled to follow the Axolotl through many stages, and several other types have been worked out both in their larval and adult stages; some of these fill up lacunæ in the series of Axolotls.