1. THIS elaborate and important monograph monopolizes the first two parts of the sixth volume of the Journal of Morphology. It is the second of a projected series on “Vertebrate Cephalogenesis.” Its predecessor was published in the same journal two years ago, and the instalment now under consideration has been anticipated by three shorter communications (Nos. 5, 7, and 8 of the literature cited) of a distinctly sensational character. The 320 pages of contents are illustrated by 26 simple woodcuts; and by 12 magnificent folding plates, printed in colour, and bearing the charmed, names of Werner and Winter.