In Amblystoma, a genus of the amphibian Urodela, one finds an enlightening approach to the study of behavior. Unlike the Anura (frogs, toads, etc.), Amblystoma does not resorb the tail in metamorphosis from the tadpole or larval stage to the adult condition. The trunk and tail, on the other hand, continue throughout life as a flexible, integrated organ, the bending of which gives the animal its power of aquatic locomotion and, subsequently, becomes the primary component of locomotion on land. This lack of anatomic and physiologic specialization in the axial organization of Amblystoma makes the animal peculiarly adapted to the study of the development of behavior, and I have taken advantage of this adaptation by observing the behavior of different species of Amblystoma from the earliest movements till the general adult pattern of action is established.
As a result of this investigation of the development of behavior a general principle