I had for years been using to myself the terms mutability of species, and transmutation of species, for want of better words to express the feeling, (amounting to a conviction) that in Time species passed insensibly into each other instead of being produced by separate acts of creation. But the idea implied by your principle of Natural Selection taken in connection with the struggle for existence is very different indeed from the vague gropings towards the light in which myself and others with various degrees of hesitation indulged.²

My faith such as it was, was founded on the following considerations. The disputes among Naturalists as to what constitutes a species the wranglings as to whether such & such were distinct species or varieties, the acknowledgment of permanent varieties, the existence of specific & still more of generic centres, of representative species in space, & in time in a geological sense, & the links (especially the rudimentary organs) that bind genera together, especially in the higher Mammalia, when living & fossil forms are considered together. The succession of small miracles required to produce certain species in a formation just a very little different from those in the preceding formation went sadly against my mental stomach & I never could reconcile myself to the idea of a Creator making a number of small experiments as it were of feeling his way in the work of Creation—   And when asked where are the perfect gradations, that show the passage of fossil species, I have always maintained that the record as shown in the succession of formations was too imperfect for us to find this & that it is not till an aberrant branch, multiplied to a vast extent, that we were likely to find fossilized any of its representatives at all.