My dear Mr. Darwin,

I enclose a specimen just received from Fritz Müller which you may perhaps like to see—a branchiated Trichopteron! You will see from his letter the special interest which attaches to the insect. The branchiæ can be seen projecting from between the segments. I must beg you to return the specimen as I will exhibit it at the next meeting of the Entom. Soc.¹

Weismann’s book is getting on—² The 1^st. essay (Seasonal dimorphism) is nearly ready for publication & about $\frac{1}{2}$ the 2^nd. essay roughly translated.

I sent an abstract of the article in Kosmos on Epicalia Acontius to Nature a long time ago but suppose it has been ‘crowded out’ as it has not yet appeared.³ It would have been very appropriate in this week’s Nature as a check upon Wallace’s restrictions upon sexual selection in his review of Grant Allen’s “Colour in Nature”.⁴ In this review Wallace states “We may also remark that the sexual allurement of a peculiar odour given out by special patches of scales on butterflies’ wings has been discovered by Fritz Müller in the genera Mechanitis, Dircenna, & Thecla, all very brilliantly coloured groups, a clear indication that colour is not a sexual allurement or we should find it most developed, not in conjunction with, but in the absence of, the attraction of odour.”⁵ The words which I have italicised are open to criticism— in fact I venture to think the argument totally fallacious. It does not follow that because colour has been acquired through Sexual Selec. the same agency should not have added other attractions in the same species. Do you concur in this?

Yours very faithfully, | R. Meldola.

Ch. Darwin Esq^re. LLD. F.R.S. &c.