I shall be quite contented if his belief in the immutability of species is at all staggered.
LETTER 87.

TO C.LYELL.
(87/1.

In the "Origin of Species" a section of Chapter X.is devoted to "The succession of the same types within the same areas, during the late Tertiary period" (Edition I., page 339).

Mr.Darwin wrote as follows: "Mr.Clift many years ago showed that the fossil mammals from the Australian caves were closely allied to the living marsupials of that continent." After citing other instances illustrating the same agreement between fossil and recent types, Mr.Darwin continues: "I was so much impressed with these facts that I strongly insisted, in 1839 and 1845, on this 'law of the succession of types,' on 'this wonderful relationship in the same continent between the dead and the living.' Professor Owen has subsequently extended the same generalisation to the mammals of the Old World.") Down, [December] 27th [1859].
Owen wrote to me to ask for the reference to Clift.

As my own notes for the late chapters are all in chaos, I bethought me who was the most trustworthy man of all others to look for references, and I answered myself, "Of course Lyell." In the ["Principles of Geology"], edition of 1833, Volume III., chapter xi., page 144, you will find the reference to Clift in the "Edinburgh New Phil Journal," No.XX., page 394.