The date is conjectured from the relationship between this letter and the letter from Sigmund Fuchs, [1877–8?].

CD probably wrote this draft in the expectation that Francis Darwin would write the reply to Fuchs’s letter of [1877–8?]; the draft is written on the back of that letter. F: father. CD alludes to the debate among zoologists regarding vertebrates and their ancestors. While many, including CD (see Descent 1: 205–6), had supported the view that vertebrates were descended from ascidians (Tunicata), others had argued that they descended from segmented worms (Annelida; see, for example, Correspondence vol. 23, letter from Anton Dohrn, 7 February 1875). Fuchs had asked whether CD agreed with Carl Friedrich Claus’s removal of tunicates from the phylum Mollusca into their own group in the most recent edition of Claus’s textbook, Grundzüge der Zoologie (Claus 1876). Although his reasons for the change were not explicit, Claus had included references to similarities between tunicates and vertebrates in both embryonic and larval stages (see letter from Sigmund Fuchs, [1877–8?] and n. 4).