the _Beagle_ Darwin saw fossil
armadillos like existing species, and on the islands of the
Galapagos group a gradually increased diversity of species of
every kind. All this suggested that species gradually become
modified. Notes gathered of facts bearing on the question.
Observes that it is the variation between one animal and
another which gives the breeder his opportunity. Reads
Malthus on Population, a work which points out the keen
struggle for existence and that favourable variations tend to
be preserved. In 1842 draws up a brief abstract of the theory
of "natural selection." In 1856 begins an elaborate work on
the same theme, but in 1858, hearing that Wallace has written
an essay advancing an independent theory of natural selection,
offers a summary of his argument to the Linnean Society
of London. Writes "The Origin of Species," which is published
most successfully, November, 1859. 35

DARWIN, CHARLES

THE DESCENT OF MAN: THE ARGUMENT IN BRIEF

Since evolution is probable for all other animals, it is
probable for man. The human form has so much in common with
the forms of other animals that community of descent is
strongly suggested. Man, like other creatures, is subject to
the struggle for existence. Evidence shows that it is likely
that man is descended from a tailed and hairy quadruped that
dwelt in trees. Man's mental power has been the chief factor
in his advance, especially in his development of language.
Conscience is due to social instincts, love of approbation,
memory, imagination and religious feeling. Sexual selection
in its effects upon human advancement. 45

WALLACE, ALFRED R.

MIMICRY AND OTHER PROTECTIVE RESEMBLANCES AMONG ANIMALS

The colours of animals are useful for concealment from their
prey, from the creatures upon which they prey. The lion is
scarcely visible as he crouches on the sand or among desert
rocks and stones. Larks, quails and many other birds are so
tinted and mottled that their detection is difficult. The
polar bear, living amid ice and snow, is white. Reptiles and
fish are so coloured as to be almost invisible in the grass
or gravel where they rest. Many beetles and other insects
are so like the leaves or bark on which they feed tha