Dear Sir

I am very much obliged to you for your interesting letter of Jan 11^th.¹ I was aware that the cells of Bees varied a little in dimensions, but did not in the least know to what a degree the variability extended.² Your statements make the proposition of some, I think, French savant that the size of the cell sh^d be the standard of all measurements, quite ludicrous.³ This variability of size agrees well with the view which we both I think take of all instincts.⁴ Your case of the 2 cells separated by a flat bottom appears to me particularly interesting.⁵

As so much has been written of late about Bees cells, I cannot but think that your facts w^d be well worth publishing in a separate paper: should you intend doing so, I sh^d be grateful for a copy.⁶ I had not heard of the fossil tadpole-nests,⁷ nor of M^r Puttnam’s paper on the cells of humble bees; I wish he had sent me a copy of it.⁸

With respect to your remark that the hexagonal cell always results from the co-operation of several bees, you must remember the comb began by the solitary female wasp.⁹ M^r F. Smith of the Brit. Museum has lately adduced in Proc. of Ent. Soc. of London several cases of hexagonal combs made by single insects, & others with hexagonal cells at the extreme circumference;¹⁰ But in the specimens which I have seen, the hexagons were not very perfect at the circumference. I am glad that you have been attending a little to this subject; I formerly found it very interesting but I have not looked over my notes for several years.¹¹

I may add that Prof. Miller carefully measured for me the thickness of the cell-walls & found great variability in their thickness.¹² With my best thanks for your kindness in writing

I remain dear Sir yours very faithfully | Ch. Darwin