 Unlike Turing’s more holistic model, in which patterns emerge from initial random instability due to interaction of multiple morphogens, Crick’s model grounds morphogenesis in simple chemical diffusion. Agutter, Malone, and Wheatley (2000) and Vecchi and Hernández (2014) argue that Crick’s model lacks explanatory power. However, Minelli (2009) suggests an updated source-sink model, informed by advances in molecular and cell biology.