Starting from the assumption that variations in primary ego and drive endowment may color the manner in which a child will experience and master each developmental step, this paper discusses problems in assessing these primary factors and in tracing their continuity in the constantly changing manifestations of later development. It was suggested that individual differences in the neonate's way of dealing with internal and external stimuli may reflect derivatives of these primary endowment factors; also, that the study of the style of development may furnish continuities in behavior otherwise obscured by changing content. Nine neonatal variables, all involving response to internal and external stimuli, were suggested for study

and hypothetical directions in which these variables may find expression in later development were outlined.