I was flicking through my copy of volume one of The Life and Letters of Thomas Henry Huxley by his son Leonard Huxley (1900) yesterday, when I came across this photograph of the fresh-faced Huxley taken shortly before he set off for New Guinea and Australia aboard HMS Rattlesnake.

I had no recollection of this photograph, although a subsequent search showed that it also appears in volume one of Adrian Desmond's biography of Huxley. But the photograph did not appear when I carried out a quick Google search for images of Huxley. So I thought I'd better publish it here to ensure that it turns up in future searches.
I'm rather pleased to own copies of the two volumes of The Life and Letters of Thomas Henry Huxley. I picked them up in a second-hand bookshop many years ago. Previously, they had resided in the Scottish Liberal Club's Gladstone Memorial Library.
See also: HMS Rattlesnake figurehead