My dear Miller,

I had no thought that you would measure thickness of walls of cells; but if you will, and allow me to give your measurements it will be immense advantage.² As it is no trouble, I send more specimens. If you measure please observe that I measured thickness of walls of hexagonal prisms not very near base: but from your very interesting remarks the lower part of walls ought to be measured—

Thank you for suggestion about how bees judge of angles and distances.³ I will keep it in mind. It is a complete perplexity to me, and yet certainly insects can rudely somehow judge of distances. There are special difficulties on account of gradation in size between worker-cells and the larger drone-cells. I am trying to test the case practically by getting combs of different species, and of our own bee from different climates. I have lately had some from W. Indies of our common bee,⁴ but cells seem certainly to be larger; but they have not yet been carefully measured. I will keep your suggestion in mind whenever I return to experiments on living Bees; but that will not be soon.

As you have been considering my little discussion in relation to L^d Brougham,⁵ and as I have been more vituperated for this part than for almost any other, I should like just to tell you how I think the case stands. The discussion viewed by itself is worth little more than the paper on which it is printed, exepting in so far as it contains 3 or 4 certainly new facts. But to those who are inclined to believe the general truth of the conclusion that species and their instincts are slowly modified by what I call natural selection, I think my discussion nearly removes a very great difficulty. I believe in its truth chiefly from the existence of the Melipona, which makes a comb so intermediate in structure between that of Humble and Hive bee; and especially from the new and curious fact of the bees making smooth cups or saucers, when they excavated in a thick wax, which saucers stood so close that hexagons were built on their intersecting edges. And lastly because when they excavated on their slip of wax, the excavation on both sides of similar smooth basins was stopped, and flat planes left between the nearly opposed basins. If my view were wholly false these cases would I think never have occurred. Sedgwick and C^o may abuse me to their hearts content,⁶ but I shall as yet continue to think that mine is a rational explanation (as far as it goes) of their method of work.

With cordial thanks for all your great kindness. | Yours very sincerely | C. Darwin