This is about a possible allusion by Alfred Parsons to Henry Holiday.

[left]: The Study at Down (from the The Century illustrated monthly magazine, v.25 1882-1883, p. 420, Indiana University Library)
Illustration from a painting (1882, from a photo) by Alfred Parsons
Engraver: J. Tynan
(Scan from original 19th century source:
Francis Darwin: The Life and Letters of Charles Darwin, Vol. 1, 1888, p. 101)

[right]: illustration by Henry Holiday to Lewis Carroll's The Hunting of the Snark, 1876

The comparison of these two images started in June 2010. Alfred Parsons may have alluded to Henry Holiday's illustration. I am not so sure about that, but if Parson played Holiday's game with Holiday's illustration, then Parsons must have manipulated the reality of Darwin's study a bit.