Genetic atomism is dead. Hereditary stability and hereditary change are both based, not on a mosaic of genes, but on the action of the gene-complex 'as a whole'. But this face-saving expression-which is now coming into increased use-is empty, like so many other holistic formulations, unless we interpolate between the gene-complex as a whole, and the individual gene, a hierarchy of genetic sub-assemblies-self-regulating holons of heredity, which control the development of organs, and also control their possible evolutionary modifications, by canalising the effects of random mutations. A hierarchy with its built-in, self-regulatory safeguards is a stable affair. It cannot be pulled in here, pulled out there, like Patou belabouring his model. It is capable of variation and change, but only in co-ordinated ways and only in limited directions.