Dear Sir

In reading your new book, an idea with regard to the erection of its feathers by a bird, & of its hair by a beast, has occurred to me, which I have thought I might dare to communicate to you.² Please p⁠⟨⁠a⁠⟩⁠rdon me if m⁠⟨⁠y⁠⟩⁠ suggest⁠⟨⁠ion⁠⟩⁠ is [1 or 2 words illeg] It seems to me that this habit must be of real use for defence. Surely a hen with its feathers ruffled, (and its head drawn back to its body) is to a great extent defended against the attack of a dog.³ Similarly the bristling mane of a lion is a great protection against the teeth of an other animal. His enemy would hardly know ‘where to have him’, & would perhaps get merely a mouthful of hair ins⁠⟨⁠tea⁠⟩⁠d of a grip of the lion’s throat. Even in the case of the monkey & snake, the snake would have greater difficulty in fixing its fangs if the hair of the monkey were erected.⁴ This defence-theory seems to me so obvious, to have so strong a primâ facie probability on its side that I cannot but think that you have rejected it with very good reason for the expression-theory.⁵ I therefore beg again that you pardon me for troubling you with this letter.

Your obed^t Servant | A. Smither

Chas Darwin. Esq. M.A. &c.