Step 1: Understanding the Problem:
Hugo de Vries conducted extensive experiments on the evening primrose plant ({Oenothera lamarckiana}) and subsequently proposed the Mutation Theory of evolution.
Step 2: Approach and Formula:
Identify the primary mechanism of evolution (speciation) proposed specifically by Hugo De Vries and contrast it with Darwinian principles.
Step 3: Detailed Explanation:
Charles Darwin posited that evolution was driven by the gradual accumulation of minor, continuous, directional variations over long periods.
In stark contrast, Hugo de Vries proposed a radically different mechanism. He suggested that evolution and the formation of entirely new species (speciation) occur suddenly due to massive, discontinuous genetic changes.
He introduced the term Saltation to describe this specific phenomenon, which he definitively defined as a "single-step large mutation."
According to his theory, these mutations are entirely random and directionless, rapidly generating new species.
Step 4: Final Answer:
According to Hugo de Vries, speciation is due to a single-step large mutation.