 Sections  2  and  3  described how the original genotype-phenotype distinction was operationalized under special, controlled conditions, namely, the growing and crossing of inbred lines raised under uniform conditions.  Section 4  laid out pathways from the experimentally based distinction: reintegrate, engineer, generalize theoretically, liken, and experiment more. Yet biology and philosophy of biology have not emphasized the need to reintegrate what has been abstracted away as a necessary step if the genotype-conception of heredity is to be extended beyond those special conditions (Figures  2  and  3)  and applied to the study of heredity for natural varying populations  (Figure 1).  Therefore, to highlight the implications of basing the genotype-phenotype distinction in controlled conditions, this section considers what control and possible reintegration might entail in the different realms reviewed so far.