If they [enlightened men] take any interest in examining, in the infancy of our species, the almost obliterated traces of so many nations that have become extinct, they will doubtless take a similar interest in collecting, amidst the darkness which covers the infancy of the globe, the traces of those revolutions which took place anterior to the existence of all nations.

Thus it cannot be denied that the masses which today form our highest mountains were originally in a liquid state; for a long time they were covered by waters which did not sustain any life.

Secondly, the nature of the revolutions which have altered the surface of the earth must have had a more decisive effect on the terrestrial quadrupeds than on the marine animals.

Nurse, it was I who discovered that leeches have red blood.[]On his deathbed when the nurse came to apply leeches

It is to them [fossils] alone that we owe the commencement of even a Theory of the Earth ... By them we are enabled to ascertain, with the utmost certainty, that our earth has not always been covered over by the same external crust, because we are thoroughly assured that the organized bodies to which these fossil remains belong must have lived upon the surface before they came to be buried, as they now are, at a great depth.

Moreover, it thus follows that not a great deal of time was needed for the large animals of the three major parts of the world to become known to the people who spent time on the coasts of those regions.

All organs of an animal form a single system, the parts of which hang together, and act and re-act upon one another; and no modifications can appear in one part without bringing about corresponding modifications in all the rest.