From the TRAnsmutation notebooks of Charles Darwin

We see gradation to mans mind in Vertebrate Kingdom, in more instincts in rodents than in other animals; & again in mans mind, in different races being unequally developed. — ? is not elephant intellectually developed amongst Pachydermata like man amongst monkeys or dog in Carnivora. —

Man in his arrogance thinks himself a great work worthy the interposition of a
deity, more humble &
I believe truer to consider him created from animals.

Study Mr. Blyths papers on Instinct. —His distinction between reason & instinct very just; but these faculties being viewed as replacing each other it is hiatus & not saltus. —

The greater individuality of mind in man is analogous to greater individuality of bodies of some animals over those of others. — The mind of different animals less divided. — But as man has hereditary tendencies, his mind is still only, divided body. language seems to supply instincts,—& those powers which allow of acquirement of language hereditary, acquirable. — therefore mans mind not so different from that of brutes.

Hard to say what is instinct in animals & what reason, in precisely same way not possible to say what habitual in man & what reasonable. Some action may be either in same individual. — is not squirrel hoarding & killing grain acquirable through hoarding from short time. — My theory must encounter all these difficulties, knowing that animals have some reason, & actions habitual, it surely is not worthy interposition of deity to teach squirrel to kill ears of corn. According to my views, habits give structure, habits precede structure, habitual instincts precede structure. — duckling runs to water before it is conscious of web-feet. —

Mr.Blyths arguments against squirrel using reason in hiding its food is applicable to My theory drives me to say that there can be no animal at present time having an intermediate affinity between two classes. — there may be some descendant of some intermediate link. — the only connection between two such classes will be those of analogy, which when sufficiently multiplied become affinity yet often retaining a family likeness, & this I believe the case. — Any animal really connecting the fish & mammalia must be sprung from some source anterior to giving off of these two families, but we see analogies between fish. — Birds same remarks.