"I could think of nothing for days after your lesson on coral reefs, but of the top of submerged continents. It is all true, but do not flatter youself that you will be believed, till you are growing bald, like me, with hard work & vexation at the incredulity in the world."

Galapagos land birds and reptiles.

No two naturalists agree on any fundamental idea [of species]. "Everything is arbitrary."

Has been with Richard Owen going over the S. American fossils.

Has worked out the non-relation between animals’ bulk and luxuriance of vegetation.

The horse once common on the Pampas. The mystery of the extinction of these animals.