f an orderly
development under the action of natural causes was there. In Darwin's
mind this at once found acceptance, and was destined to a fruition its
author had expressly disclaimed.

The narrative of this voyage, as subsequently written, describes the
islands visited by the _Beagle_ in crossing the Atlantic Ocean. The
contrast between the simple and general interest in these islands and
the care with which Darwin described the Galapagos and the Keeling
Atoll visited later in the voyage are speaking evidence of the rapid
development going on in the mind of the young naturalist.

Reaching the shore of South America, Darwin first turns to its
geology. But before long the animal life attracts his attention. In
the Brazilian forest Darwin had his first experience of the wealth of
animal and plant life in the tropics, and, like all naturalists, he
was very enthusiastic over it. Among the animals that particularly
attracted his attention was the sloth, a peculiar creature climbing
slowly about the trees, small of size and sluggish of habit. Another
animal that interested him greatly was the little armadillo with its
interesting habit of curling up in its plated skin.

Captain Fitzroy soon finished what work he was required to do in this
neighborhood, and Darwin was called back to the _Beagle_ to continue
his voyage. When they arrived at the mouth of La Plata their most
serious work began. Here there was much tedious charting for Fitzroy,
and Darwin could now leave the vessel for a lengthy trip on shore.
This was doubly welcome. Seasickness was nearly constant with Darwin
while on this entire voyage and every opportunity to work on land was
eagerly seized. This region, too, was rich in objects of interest and
in strange people. While exploring the pampas, beyond Buenos Ayres,
Darwin came across the skeletons of the great mammals some of which
Cuvier had previously described. He studied these bones with much
care, and recognized at once in the megatherium a great similarity in
structure to the sloth he had seen in Brazil. The enormous skeletons
of the glyptodons struck him also as strangely similar to that of the
armadillo. One evening, seated alone in the broad expanse of the
pampas, the idea suddenly swept over him, stimulated, of course, by
his study of Lyell: "Can it be that the little armadillo and the sloth
of to-day are the degenerate descendants of the enormous megatherium
and glyptodon of the past?" But his mind