Dear M^r. Darwin

I have to thank you and the excellent translator very much for the opportunity of reading Malm’s paper on Flat-fish¹

My own ignorance of the languages of Scandinavia renders a translation of any portion of its zoolo-literature most acceptable, and when the subject is of such interest as the production of asymmetry in the Pleuronectidæ my obligations for being put in possession of it are especially great.²

Malm’s observations appear to be quite reliable. I think we may regard the retention of the eye on a level with the surface of the head as established by them, and its migration through the skull as untenable.³

I have been reminded by this paper of another point which has doubtless also struck yourself. I refer to the apparent connexion between the stalked condition of the eye in the podophthalmic crustacea and the habits of the animal. I believe that in the Podophthalmia the direction of locomotion in swimming is always retrograde— it certainly is so in the macrourous species, and the connexion between this form of locomotion and the possession of an eye seated on a moveable stalk which enables it to be turned in the direction of the locomotion is obvious.⁴

The bracyurous forms moreover are macrourous and eminently natatory with retrograde progression in the zoea stage with—if I remember rightly—the eye-stalks excessively developed in this stage.⁵

I do not think that the sessile-eyed Crustacea are retrograde in their motions. You will perhaps remember how it is with the young barnacle.

Believe me | Ve⁠⟨⁠ry⁠⟩⁠ sincerly yours | ⁠⟨⁠Ge⁠⟩⁠o. J. Allman

I return the translation of Malms paper by this post.