 Several of the programs of reintegration sketched in  section 5  rest on the idea that development of traits will eventually be understood in terms of a composite of the influences of DNA variants on the organism. An alternative approach is to observe that germ cells are organized structures, which means that development is always a process of further organization emerging from initial organization. That emphasis was evident, not only in developmental mechanics (Entwickslungsmechanik), but also in a mid-twentieth century form of epigenetics centered on embryological or developmental pathways. Conrad Waddington, for example, undertook experiments on variation in certain characters that was originally seen only in response to an environmental stress, e.g., enlarged anal papillae (a fleshy protuberance) of Drosophila larvae that arose in higher salt concentrations (Waddington 1959). In populations that had been selected for that responsiveness, eventually the trait occurred even when that stress was withdrawn. Waddington’s interpretation is that a genotype (in the sense of a specific set of pairs of genes) had arisen in the population that switched on development of large papillae. Presumably, this could happen through reassortment of genes into new genotypes, not a random mutation. An alternative hypothesis, which places more emphasis on the dynamics of development, is that, if many pathways in a non-inbred population can produce the same response (e.g., enlarged anal papillae in response to salt), selection results in a population of individuals that have a concentration or redundancy of the various pathways. If pathways arise within this concentration where large papillae develop without the salt stress, that is not a logical process to be modeled by population genetic or quantitative genetic models, but a contingent outcome of the dynamics of development in a realm in which a variety of genotypes can influence a variety of paths to a trait. In this light, to call traits phenotypes, and thus suggest that they have a direct association with a specific genotype, is to make it more difficult to conceive and pursue a program of reintegration in which researchers examine cases of traits that are acquired as an appropriate response to environmental condition and then increase in frequency in a population. Moreover, even if such cases turn out not to be common, they trouble the premise that the individual-to-individual barrier to a trait being transmitted back into the genotype barrier means that acquired characters cannot increase in a population during evolution.