“But if, as has been argued in preceding chapters, genes do not create traits according to a plan written in their very structure, even by operating on conveniently available “raw materials,” if phenotypic characteristics arise only when sufficient interactants are present in the proper place and at the proper time, and if all these factors are therefore given comparable causal and formative significance, then defining heredity as the passing on of all developmental conditions, in whatever manner, is preferable to defining it by genetic information.”