My dear Sir

I have often reflected over the two cases to which you refer. When working on Orchids, I have often & long watched the species of Ophrys, because R. Brown thought that their supposed likeness to insects served to keep them away.² This might possibly be advantageous to the Bee Ophrys; but certainly not to the others, as they absolutely require the aid of insects for fertilisation, though they get this aid but rarely or rather rarely.—

I believe (& D^r Hooker³ who happens to be here agrees with me) that the resemblance is fanciful;⁴ the flowers are odd looking & insects are the most natural standard of comparison. Who ever saw a Bee with violet wings like the petals of the Bee Ophrys? The Fly Ophrys is more like. Hooker believes that the Spider ophrys is so called simply from the curved marks on the Labellum like the marks on the backs of some Epeiræ. The Butterfly orchis has hardly any resemblance to a butterfly, & so with some foreign orchids which have received all kinds of fanciful names.—⁵

Your second case seems to me much more difficult: for my own part I believe the beauty of shells is altogether incidental on other causes & of no service whatever to the animals. The form depending on manner & symmetry of growth, & the colour being incidental on the chemical nature of the constituent element of the shell.⁶ To explain what I mean,—nothing is more beautiful than arterial blood, yet no one supposes that the colour has been gained for the sake of colour or beauty, though it gives beauty to the cheeks of Caucasian maidens. Or again, & this is a better illustration; the extreme beauty of the Eolidæ is due to their biliary secretions & organs being seen through their transparent tissues; but no one will suppose that their bile has been coloured for beauty, but is incidental on its chemical nature, as much as the recently discovered aniline colours.⁷ Nothing in this note can, I think, be of the least service to you, but you are welcome to use it as [illeg] from me, if you think fit. I have introduced these illustrations in my M.S. on sexual selection.—⁸

Pray believe me | My dear Sir | Yours sincerely | Ch. Darwin

Pray forgive this untidy & ill-expressed letter from want of time.—

Bearing in mind the magnificent colours of many artificial organic substances made by elements, it w^d be wonderful if such had not been produced under nature, without being of any special use: if there had been no such beautiful colours, this fact w^d. have had been to have been accounted for—

I think of the beauty & splendour of the withering leaves in an American forest.—