From my observations it is clear that, in the opossum of the first day in the pouch, there are functional commissural relations at the level of the brachial plexus, a descending (motor) path as far caudad as the lower thoracic level (for stimulation of the m. rectus abdominis) and an ascending pathway from the lumbosacral region to the upper cervical segments or the brain; also that the hind legs become motile on the 7th day in the pouch, and at a more advanced stage they become integrated with the fore legs SO as to execute the walking gait before they are capable of reflex action. In the development of walking, therefore, in the opossum as in amblystoma (Coghill7), the gait is essentially a total pattern of action while reflexes serve for orientation and adjustment to surfaces.