Die Entwicklungsreihe besteht demnach aus 9 Gliedern.
The developmental series thus consists of 9 members.

developmental series = Entwicklungsreihe Sherwood only has “series”. Entwicklung also has a mathematical meaning; see p. 17, s. 6.

members = Glieder Bateson has “classes”, Sherwood “terms”. This word as well was routinely used in mathematics to refer to the elements manipulated in combinatorics; see Andreas von Ettingshausen, Die combinatorische Analysis als Vorbereitungslehre zum Studium der theoretischen höhern Mathematik (Vienna: Wallishausser, 1826), passim, but especially p. 85, where the author deals with polynomials. As the English “member”, Glied originally designates body parts, especially extremities, but was used metaphorically for any part of a whole (such as a member of a political organisation); see Jacob and Wilhelm Grimm, Deutsches Wörterbuch, online-edition, s.v. “glied” (1936), VIII. Mendel also uses the term to designate taxonomic units or elements within his experimental design (see p. 15, s. 12 and p. 13, s. 6). In English, the word “term” has become the common expression in mathematical contexts, so Sherwood’s translation is more idiomatic. We have chosen the more literal “member”, throughout our translation in order to preserve the organicist connotations.