ill not be inclined to
consider the suggestion far-fetched.) The observation is recorded in
one of the manuscript journals kept by the great explorer during his
journey. I owe the opportunity of studying it to the kindness of Mr
Francis A. Burchell of the Rhodes University College, Grahamstown. The
following account is given under the date July 5, 1812, when Burchell
was at the Makkwarin River, about half-way between the Kuruman River and
Litakun the old capital of the Bachapins (Bechuanas): "I found a curious
little Crassula (not in flower) so snow white, that I should never has
(have) distinguished it from the white limestones... It was an inch high
and a little branchy,... and was at first mistaken for the dung of birds
of the passerine order. I have often had occasion to remark that in
stony place(s) there grow many small succulent plants and abound insects
(chiefly Grylli) which have exactly the same colour as the ground and
must for ever escape observation unless a person sit on the ground and
observe very attentively."

The cryptic resemblances of animals impressed Darwin and Wallace in
very different degrees, probably in part due to the fact that Wallace's
tropical experiences were so largely derived from the insect world, in
part to the importance assigned by Darwin to Sexual Selection "a
subject which had always greatly interested me," as he says in his
"Autobiography", ("Life and Letters", Vol. I. page 94.) There is no
reference to Cryptic Resemblance in Darwin's section of the Joint Essay,
although he gives an excellent short account of Sexual Selection (see
page 295). Wallace's section on the other hand contains the following
statement: "Even the peculiar colours of many animals, especially
insects, so closely resembling the soil or the leaves or the trunks on
which they habitually reside, are explained on the same principle; for
though in the course of ages varieties of many tints may have occurred,
YET THOSE RACES HAVING COLOURS BEST ADAPTED TO CONCEALMENT FROM THEIR
ENEMIES WOULD INEVITABLY SURVIVE THE LONGEST." ("Journ. Proc. Linn.
Soc." Vol. III. 1859, page 61. The italics are Wallace's.)

It would occupy too much space to attempt any discussion of the
difference between the views of these two naturalists, but it is clear
that Darwin, although fully believing in the efficiency of protective
resemblance and replying to St George Mivart's contention that Natural
Selection was incompetent to produce it (