Dear Sir

I have been very much interested by your Volume on the formation of vegetable mould through the action of worms, which you had the great kindness of sending me.¹ I had often observed the freqent occurrence of these worms and their castings, and was acquainted with an account of von Hensen’s paper,² but had not the least suspicion of the prominent part, worms have taken in the formation of the vegetable mould, as I learn from your observations. After reading the first chapters of your book, I have been attending to the habits of worms, and had the good fortune of repeating some of your interesting observations, but it seems that time and wheather are not now favourable to these experiments.

For some time I have been studying the causes of the variations of plants, as described in your Treatise on the variations of animals and plants under domestication,³ and have endeavoured to collect some more facts on this theme. In your Origin of Species you have promised a Volume on the variations of animals and plants in the wild state and I very much hope that some day you will have the kindness of fulfilling this promise and of making us acquainted with the results of your investigations on this most interesting subject.⁴ I have always been especially interested in your hypothesis of Pangenesis, and have collected a series of facts in favour of it, but I am sure, that your promised publications will contain much more evidence on all such points, as I would for many years be able to collect.⁵

With many thanks for your kind present. | Yours sincerely | Hugo de Vries.