On Comparative Longevity in Man and the Lower Animals-E. Ray Lankester

Movement of Animals (or On the Motion of Animals; Greek Περὶ ζῴων κινήσεως; Latin De Motu Animalium) begins with a discussion of the physics of motion and asks whether God, the Unmoved Mover, exists outside of our Universe. Progression of Animals (or On the Gait of Animals; Greek: Περὶ πορείας ζῴων; Latin: De Incessu Animalium) asks why animals have the parts they do and to what end these parts are possessed. - Summary by Geoffrey Edwards