ther
observations on this mollusc, and I hope that you will give a figure and
if possible a coloured figure.

With all good wishes from an old brother naturalist,

I remain, Dear Sir,

Yours faithfully,

Charles Darwin.

Professor E.B. Wilson has kindly given the following account of the
circumstances under which he had written to Darwin: "The case to which
Darwin's letter refers is that of the nudibranch mollusc Scyllaea,
which lives on the floating Sargassum and shows a really astonishing
resemblance to the plant, having leaf-shaped processes very closely
similar to the fronds of the sea-weed both in shape and in colour. The
concealment of the animal may be judged from the fact that we found
the animal quite by accident on a piece of Sargassum that had been in a
glass jar in the laboratory for some time and had been closely examined
in the search for hydroids and the like without disclosing the presence
upon it of two large specimens of the Scyllaea (the animal, as I recall
it, is about two inches long). It was first detected by its movements
alone, by someone (I think a casual visitor to the laboratory) who was
looking closely at the Sargassum and exclaimed 'Why, the sea-weed is
moving its leaves'! We found the example in the summer of 1880 or 1881
at Beaufort, N.C., where the Johns Hopkins laboratory was located for
the time being. It must have been seen by many others, before or since.

"I wrote and sent to Darwin a short description of the case at the
suggestion of Brooks, with whom I was at the time a student. I was, of
course, entirely unknown to Darwin (or to anyone else) and to me the
principal interest of Darwin's letter is the evidence that it gives of
his extraordinary kindness and friendliness towards an obscure youngster
who had of course absolutely no claim upon his time or attention. The
little incident made an indelible impression upon my memory and taught
me a lesson that was worth learning."

VARIABLE PROTECTIVE RESEMBLANCE.

The wonderful power of rapid colour adjustment possessed by the
cuttle-fish was observed by Darwin in 1832 at St Jago, Cape de Verd
Islands, the first place visited during the voyage of the "Beagle".
From Rio he wrote to Henslow, giving the following account of his
observations, May 18, 1832: "I took several specimens of an Octopus
which possessed a most marvellous power of changing its colours,
equalling any chameleon, and evidently accommodating the changes to the
c