Which book by Charles Darwin did Thomas Henry Huxley defend in public debates?

Thomas Henry Huxley, often referred to as "Darwin’s bulldog," famously defended Charles Darwin’s seminal work, On the Origin of Species, in public debates.12

Huxley utilized the book as a powerful tool in his campaign to establish an independent scientific elite, framing the discourse around evolution and natural selection in clear, non-miraculous terms. A defining moment of this advocacy occurred during a debate at the 1860 meeting of the British Association for the Advancement of Science in Oxford, where he challenged the conservative views of Samuel Wilberforce regarding human ancestry.1