To F. S. Arnold   31 December [1878]¹

Dear Sir

I do not think that the two passages essentially contradict each other, but if I had to write them again I would owing to your criticism slightly modify them.² The forms which most jostle each other I believe to be generally “varieties of the same species, & species of the same genus or of related genera”.— I would now insert “closely related genera”. In the other passage (p. 89) the forms which are able to live when exposed to severe competition are not varieties of the same species or sub-species but “belong to what we call distinct genera and orders”.— I would now add “quite distinct genera” or something to the same effect. But I know well that I often fail to think clearly & to express myself clearly.