ABSTRACT
The immediate mechanism of the process is explained perfectly, and usually, to a biologist, that is sufficient. The same is probably true in biology: every epigenetic or homeostatic process is susceptible of a double interpretation, deterministic and finallistic. The old idea that sexuality is necessary in some way to recharge the morphogenetic potential has been abandoned in favor of finalistic arguments on the benefits of genetic exchange; perhaps this merits re-examination. None of the transformations that the authors has encountered is fundamentally irreversible; they are only difficult to reverse. The preceding scheme affords a good explanation of the classical law of recapitulation according to which the embryo retraces its phylogeny during development. In respect to evolution, there is a great difference between bacteria and Metazoa. The bacterial mechanism is relatively rigid, and a modification of any importance in the environment requires, almost ipso facto, a modification of the genome, a mutation.
