his classical paper. Such an arrangement is inconvenient, and I have
followed Wallace in keeping the two categories distinct.

The visible colours of animals are far more commonly adapted for
Protective Resemblance than for any other purpose. The concealment
of animals by their colours, shapes and attitudes, must have been well
known from the period at which human beings first began to take an
intelligent interest in Nature. An interesting early record is that of
Samuel Felton, who ( Dec. 2, 1763) figured and gave some account
of an Acridian (Phyllotettix) from Jamaica. Of this insect he says
"the thorax is like a leaf that is raised perpendicularly from the
body ¹."

Both Protective and Aggressive Resemblances were appreciated
and clearly explained by Erasmus Darwin in 1794: "The colours of
many animals seem adapted to their purposes of concealing them-
selves either to avoid danger, or to spring upon their prey ²."

Protective Resemblance of a very marked and beautiful kind is
found in certain plants, inhabitants of desert areas. Examples ob-
served by Burchell almost exactly a hundred years ago have already
been mentioned on p. 273. In addition to the resemblance to stones
Burchell observed, although he did not publish the fact, a South
African plant concealed by its likeness to the dung of birds ³. 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 Makkwárin 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 color as the ground and
must for ever escape observation unless a person sit on the ground
and observe very attentively."

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