F.J.A. Hort played a major role in bringing the textual problem associated with Jn 1:18b to light (F.J.A. Hort. Two Dissertations. London: Macmillan, 1876). These variants are discussed further in Elizabeth Harris' Prologue and Gospel: The Theology of the Fourth Evangelist (Sheffield: Sheffield Academic Press, 1994). She outlines the three readings of this controversial text as follows:
(1) hO MONOGENHS hUIOS
(2) MONOGENHS QEOS (hO MONOGENHS QEOS)
(3) hO MONOGENHS
The Byzantine text (including A and C) contain reading number (1). The Western tradition also has this variant in the OL, Syriac and "what came to be called the Caesarean tradition, fam 1, fam 13" (Harris, 102).
Harris also notes that there is evidence in the Fathers for this reading, although the patristic corpus is difficult to evaluate since there are times when it is not clear if an early Father is citing Jn 1:18 or not (Ibid).
Number (2) is the variant contained in Sinaiticus, B and C and L, P66 and P75 (hO MONOGENHS QEOS), the Peshitta, the Harclean margin, the Coptic boh., Ethiopic and the Arabic Diatessaron (Ibid). Irenaeus likewise claims that some Gnostics such as Valentinus preferred the lectio, MONOGENHS QEOS.
The problem with option (3) above is that there is "no Greek MS support" for this variant (Ibid). J.N. Sanders and B.A. Mastin (A Commentary on the Gospel According to St John. London: A & C Black, 1968. Page 85) note that hO MONOGENHS appears in the Latin Vulgate, Ephrem, Aphraat, Cyril of Jerusalem and Nestorius. Despite such lack of Greek MS support, however, they think that this reading is "to be preferred," and Sanders and Mastin translate it: "No one has ever yet seen God; the only-begotten, who is in the bosom of the Father, is the one that revealed
The rendering of Mastin and Sanders appears to sidestep the problems that usually accompany this verse. But is this reading truly to be preferred? After a stringent analysis, Elizabeth Harris concludes that MONOGENHS QEOS, if correct, would not only round off the statement made at the beginning of the prologue (KAI QEOS HN hO LOGOS), but it would also prepare the way for other so-called divine prerogative motifs in John's Gospels. While I prefer to bracket the question of John's ontological teaching vis-a-vis the Son in this submission, it seems clear that the MS evidence supports reading number (2).
Note what J.H. Bernard also writes in the first volume of his critical commentary about John's Gospel (A Critical and Exegetical Commentary on the Gospel According to St John. 2 vols. Edinburgh: T & T Clark, 1928):
"This [MONOGENHS QEOS] is the reading of aleph, B C *L 33 (the best of the cursives), Peshitta, Clem. Alex., Origen, Epiphanius, etc., while the rec. hO MONOGENHS hUIOS is found in all other uncials (D is lacking from v. 16 to 3:26) and cursives, the Latin vss. and Syr. cur. (Syr. sin. is lacking here) Chrysostom and the Latin Fathers generally. An exhaustive look at the textual evidence was made by Hort, and his conclusion that the true reading is MONOGENHS QEOS has been generally accepted. There can be no doubt that the evidence of MSS., versions, and Fathers is
overwhelmingly on this side" (Bernard, page 31).
But vide Edwyn Clement Hoskyns. The Fourth Gospel (Volume 1). London: Faber and Faber, 1940. Consult pp. 150-152.