From F. J. Cohn 9 January 1875

Schweidnitzer Stadtgraben Nro. 26. | Breslau

9 January 1875

Highly honoured Sir

It is not without embarrassment that I receive your so very kind letter of the first day of the year; if according to the old belief the blessing of the wise brings luck, then the kind wishes that you bestowed upon me must herald a happy year for me. I return your good wishes with all my heart; may the year that has just begun, and many more beyond that, grant you the opportunity to discover new facts, new thoughts for humanity, and to enjoy with undiminished vigour the fruits of your intellectual endeavours, as well as the veneration of your contemporaries.

These days I have been very busy with the preparations for the golden jubilee of my teacher and friend Prof. Goeppert, who, like no other naturalist in our circle, has won the affection of his fellow citizens through his truly humane conduct as an academic teacher. A great number of celebratory gifts, scientific and other, have been prepared for this occasion by friends both local and abroad, and I myself will send you my publication in his honour, on “die Entwicklungsgeschichte der Gattung Volvox”, within the next few days. It is an account of the most remarkable organisation and reproduction of this microscopic “cell state”, and it sheds considerable light on the lowest orders of life. May I also take this opportunity to direct your attention to the fact that in an exceedingly primitive living being, that is scarcely more organised than Bathybius, the building instinct, the capacity to build a shelter for itself from foreign matter, is well developed. I mean the genus Difflugia, a common freshwater species-rich group of the family of Rhizopoda. Their plasma body is not naked like that of Amoeba, nor does it form a corneous or calcareous casing by secretion, like Arcella and the Foraminifera; rather, like the larvae of Phryganeidae, Volvox constructs a casing for itself by gluing together grains of sand, the cell walls of diatoms, and other corpuscles in the water. Such an activity on the lowest level of organisation is mysterious.

Though it has long been printed, my paper on Aldrovanda and Utricularia is still awaiting distribution, because it will appear in a volume whose concluding essay (on bacteria) I have not yet been able to finish.