Summary

Both JDH’s and Bates’s letters are excellent. JDH has said all that can be said against direct effect of conditions, but CD still sticks to his own and Bates’s side. CD should have done what JDH suggests (since naturally he is pleased to attribute little to conditions) – viz., started on the fundamental principle that variation is innate and stated that afterwards, perhaps, this principle would be made explicable. Variation will show that "use and disuse" have some effect. Does not believe in perfect reversion. Demurs at JDH’s "centrifugal variation"; the doctrine of the good of diversification amply accounts for variation being centrifugal.

The wonderful mechanism of Mormodes ignea.

Summary

Gives CD advice on the illness of one of his sons [presumably Horace].

Summary

Variations are centrifugal because the chances are a million to one that identity of form once lost will return.

In the human race, we find no reversion "that would lead us to confound a man with his ancestors".