My dear Miller

I thank you much for your letter.² Had I seen the interest of my remark I would have made many more measurements though I did make several. I stated the facts merely to give the general reader idea of thickness of walls.³

Especially if I had seen that the fact had any general bearing I should have stated that as far as I could measure, the walls are by no means perfectly of the same thickness. Also I should have stated that the chief difference is when the thickness of walls of the upper part of the hexagon and of the pyramidal basal plates are contrasted    Will you oblige me by looking with a strong lens at the bit of comb, brushing off with a knife the upper thickened edges, and then compare, by eye alone, the thickness of walls there with the thickness of the basal plates, as seen in any cross section. I should very much like to hear whether, even in this way, the difference is not perceptible. It is generally thus perceptible by comparing the thickness of the walls of the hexagon (if not taken very close to the angle) near to the basal plates, where the comparison by eye is of course easier. Your letter actually turned me sick with panic, from not seeing any great importance of fact, till I looked at my notes, I did not remember that I made several measurements.⁴ I have now repeated some⁵ measurements roughly with same general results but difference I think is hardly double.⁶

I should not have mentioned the thickness of the basal plates at all, had I not thought it would give an unfair notion of the thickness of the walls, to state the lesser measurements alone—

With cordial and sincere thanks | Yours very truly | C. Darwin