The recipient has been identified as Williams & Norgate, the booksellers who distributed the monograph series Fauna und Flora des Golfes von Neapel und der angrenzenden Meeres-Abschnitte in London (see letter from Anton Dohrn, 18 February 1881). The date is taken from the dealer’s catalogue.

CD may have decided to subscribe to Fauna und Flora des Golfes von Neapel und der angrenzenden Meeres-Abschnitte after seeing a notice in Nature, 3 February 1881, pp. 315–16, stating that the work did not yet have any English subscribers. He would have received Williams & Norgate’s account before the arrival of the letter from Anton Dohrn, 18 February 1881, telling him that he would receive the publication gratis.