General aspects of the human ontogenesis are analyzed theoretically from the view point of behavioural biology. The functional integration of the three levels of individual development--actual genesis, ontogenesis, phylogenesis--leads the author to the term "hologenesis". Based on the concept of hologenesis developmental problems are discussed in terms of behavioural biology. In this context behaviour is defined as the organismic interaction with the environment on the basis on information of the hologenetic process. Behavioural data on fetal, neonatal, and postnatal life are discussed in relation to interaction with the peristatic milieu.